mold composition and method for detecting ceramic inclusions

专利摘要:
mold composition and method for detecting ceramic inclusions. The present disclosure relates to a titanium-containing article casting mold composition comprising calcium aluminate and a neutron ray or x-ray detectable element. Moreover, the present embodiments teach a method for detecting subsurface ceramic inclusions in a titanium or titanium alloy smelter by combining calcium aluminate, a radiographically denser element than calcium aluminate and a liquid to form a slurry; forming a mold having calcium aluminate and the radiographically dense element from the slurry; introducing a metal containing titanium aluminide into the mold that carries a radiographically dense element; solidifying said titanium aluminide-containing metal to form an article in the mold; Removing the solidified metal article containing titanium aluminide from said mold; subjecting the solidified article containing titanium aluminide to a radiographic inspection to provide a radiograph; and examining said radiograph for the presence of the dense element radiographically on or in the article.
公开号:BR112014007525B1
申请号:R112014007525-5
申请日:2012-09-05
公开日:2018-12-04
发明作者:Bernard Patrick Bewlay；Brian Ellis；Joan McKIEVER；Michael WEIMER
申请人:General Electric Company；
IPC主号:

专利说明:

(54) Title: MOLD COMPOSITION AND METHOD FOR DETECTING CERAMIC INCLUSIONS (73) Holder: GENERAL ELECTRIC COMPANY, American Society. Address: 1 River Road, Schenectady, New York 12345, UNITED STATES OF AMERICA (US) (72) Inventor: BERNARD PATRICK BEWLAY; BRIAN ELLIS; JOAN MCKIEVER; MICHAEL WEIMER.
Validity Period: 20 (twenty) years from 09/05/2012, subject to legal conditions
Issued on: 12/04/2018
Digitally signed by:
Liane Elizabeth Caldeira Lage
Director of Patents, Computer Programs and Topographies of Integrated Circuits
1/42 “MOLD COMPOSITION AND METHOD FOR DETECTING CERAMIC INCLUSIONS”
Field of the Invention [001] The present invention relates in general to casting mold compositions and methods for melting titanium and titanium alloys.
Background of the Invention [002] Modern gas turbines, especially aircraft engines, must satisfy the highest demands in terms of reliability, weight, power, economy and operational service life. In the development of aircraft engines, material selection, the search for suitable new materials, as well as the search for new production methods, among other things, play an important role in reaching standards and meeting demand.
[003] The materials used for aircraft engines or other gas turbines include titanium alloys, nickel alloys (also called superalloys) and high hardness steels. Titanium alloys are generally used for compressor parts, nickel alloys are suitable for hot aircraft engine parts, and high hardness steels are used, for example, for compressor housings and turbine housings. Highly loaded or stressed gas turbine components, such as components for a compressor, for example, are forged parts. The components for a turbine, on the other hand, are usually manufactured as investment castings.
[004] Although investment casting is not a new process, the investment casting market continues to grow as demand for more intricate and complicated parts increases. Because of the high demand for high quality, precision castings, there is continually a need to develop new ways of making castings by
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2/42 faster, more efficient, inexpensive and higher quality investments.
[005] Conventional investment mold compounds consisting of fused silica, cristobalite, plaster or the like, which are used in the foundry jewelry and dental prosthetics industries are not suitable for casting reactive alloys, such as titanium alloys. One reason is that there is a reaction between mold titanium and the investment mold. It is difficult to cast by investment titanium and titanium alloys and similar reactive metals in ceramic molds because of titanium's high affinity for elements such as oxygen, nitrogen and carbon. At high temperatures, titanium and its alloys can react with the mold face coating.
[006] The properties of the final casting are greatly deteriorated if any reaction occurs between the molten alloy and the mold. The form of this deterioration can include a poor surface finish due to gas bubbles, or in more serious cases, the chemistry, microstructure and properties of the foundry are compromised. Roughness and / or pitting on the surfaces of cast alloy components can reduce aerodynamic performance, for example, in turbine blade applications, and increase wear and friction in reciprocating or turning part applications. Therefore, there is a need in the art for new, practical and useful casting mold compositions and methods for detecting inclusions in reactive alloys, such as titanium alloys.
Description of the Invention [007] Aspects of the present invention provide foundry mold compositions, methods for casting and foundry articles that overcome the limitations of the prior art. Some aspect of the invention can be directed towards the manufacture of components for the aerospace industry, for example, turbine engine blades. Additional aspects
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3/42 can be used to manufacture a component in any industry, in particular, the same components that contain titanium and / or titanium alloys.
[008] One aspect of the invention is a mold composition for melting an article containing titanium comprising: a calcium aluminate cement comprising calcium monoaluminate, calcium dialuminate and mayanite; and a neutron or X-ray detectable element. Another aspect of the present invention is an article containing a titanium die-casting composition, comprising calcium aluminate; and a neutron or X-ray detectable element. In one embodiment, the calcium aluminate cement forms an intrinsic face coating of less than about 100 microns when the mold composition forms a mold. In one embodiment, the elements detectable by neutron ray or X-ray are mixed within the mold. In another embodiment, the elements detectable by neutron ray or X-ray are mixed within the mold and become part of the intrinsic face coating. In one embodiment, the mold composition does not have an intrinsic face coating.
[009] In one embodiment, the mold composition additionally comprises oxide particles. The oxide particles may comprise at least one of aluminum oxide particles, magnesium oxide particles, calcium oxide particles, zirconium oxide particles and titanium oxide particles. In addition, in some cases, the oxide particles comprise hollow oxide particles, for example, the hollow oxide particles comprise hollow aluminum oxide particles. In a specific embodiment, the oxide particles are aluminum oxide particles.
[010] In another embodiment, a neutron ray or x-ray detectable element comprises iterium, hafnium, gadolinium, tungsten, thorium,
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4/42 uranium, yttrium, dysprosium, erbium, cerium and compositions thereof. The neutron or X-ray detectable element can be in the range of about 1 to about 4 weight percent in the mold composition. The radiographically dense element may be radiographically denser than the oxide particles. In one embodiment, a radiographically dense element is radiographically denser than calcium aluminate and comprises one or more of iterbium, hafnium, gadolinium, tungsten, thorium, uranium, yttrium, dysprosium, erbium, cerium and compositions thereof.
[011] One aspect of the present invention is a method for detecting ceramic inclusions below the surface in a titanium or titanium alloy foundry, said method comprising: combining calcium aluminate, at least one radiographically denser element than that calcium aluminate and a liquid to form a slurry; forming a mold that has the calcium aluminate and the radiographically dense element from the slurry; introducing a metal containing titanium aluminide into the mold that bears a dense element radiographically; solidifying said metal containing titanium aluminide in order to form an article in the mold; removing the solidified metal article containing titanium aluminide from said mold; subject the solidified article containing titanium aluminide to a radiographic inspection in order to provide a radiography; and examining said radiography for the presence of the radiographically dense element on or in the article.
[012] In one embodiment, the method additionally comprises removing the dense element radiographically from the article. The removal of the radiographically dense element from the article may comprise one or more stages of machining, grinding, polishing or welding. The combining step can further comprise combining oxide particles with the slurry. In one embodiment, the oxide particles comprise
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5/42 hollow oxide particles, for example, hollow aluminum oxide particles.
[013] In one embodiment, the method comprises minimizing the presence of mold material inclusions in cast articles containing titanium aluminide. The cast article containing titanium can comprise an engine or a turbine, or a component of a turbine. For example, the cast article containing titanium comprises a turbine blade. The cast article containing titanium may be an engine containing titanium aluminide, a turbine containing titanium aluminide or a turbine blade containing titanium aluminide.
[014] One aspect of the present invention is a mold composition comprising: calcium aluminate cement comprising calcium monoaluminate, calcium dialuminate and mayanite; and at least one element denser radiographically than calcium aluminate cement. Another aspect of the present invention is a mold composition that comprises calcium aluminate and at least one radiographically denser element than calcium aluminate. In one embodiment, the mold composition additionally comprises oxide particles. In a related embodiment, the radiographically dense element is additionally more radiographically dense than the oxide particles.
[015] Another aspect of the present invention is a mold composition for melting articles containing titanium, which comprises calcium aluminate; and a neutron or X-ray detectable element. For example, one aspect of the present invention may be uniquely suitable for providing mold compositions for use in molds for casting articles or components containing titanium and / or titanium alloy, for example. example, turbine blades that contain titanium.
[016] These and other aspects, features and advantages of this invention will become apparent from the detailed description below of
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6/42 various aspects of the invention taken in conjunction with the attached drawings.
Brief Description of the Drawings [017] The matter, which is considered to be the invention, is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features and advantages of the present invention will be readily understood from the following detailed description of aspects of the invention taken in conjunction with the attached drawings in which:
[018] Figure 1 is a diagram depicting the percentage of aluminum oxide on the X axis and the temperature on the Y axis, showing various ranges of calcium oxide-aluminum oxide composition for calcium aluminate cements, and shows percentages and temperature ranges of aluminum oxide in particular for the compositions according to the revealed achievements.
[019] Figures 2a and 2b show an example of the mold microstructure after high temperature fire discharges. The backscattered electron scanning microscope images of the cross-section of the mold subjected to a fire discharge at 1,000 degrees Celsius are shown, in which Figure 2a points to the alumina particles present and Figure 2b points to the calcium aluminate cement .
[020] Figure 3a and Figure 3b show an example of the mold microstructure after high temperature fire discharges. The backscattered electron scanning microscope images of the cross-section of the mold subjected to a fire discharge at 1,000 degrees Celsius are shown, in which Figure 3a points to a calcium aluminate cement and to precisely sized alumina particles present and Figure 3b points to an alumina particle.
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7/42 [021] Figure 4a and Figure 4b show an example of the mold microstructure after high temperature fire discharges. The backscattered electron scanning microscope images of the cross-section of the mold subjected to a fire discharge at 1000 degrees Celsius are shown, in which Figure 4a points to a large-scale alumina particle and Figure 4b points to a particle of calcium monoaluminate.
[022] Figure 5 shows an example of the mold microstructure after high-temperature fire discharges, which shows alumina and calcium monoaluminate, in which the calcium monoaluminate reacts with alumina to form calcium dialuminate, and in which the mold in one example is subjected to a fire discharge in order to minimize a mayanite content.
[023] Figure 6 shows an example of the mold microstructure after high temperature fire discharges, which shows alumina and calcium monoaluminate, in which the calcium monoaluminate reacts with alumina to form calcium dialuminate, and in which the mold is subjected to a fire discharge in order to minimize a mayanite content.
[024] Figure 7 shows X-ray images in plan view of a molten titanium aluminide article. Figure 7a shows an X-ray image, with arrows pointing to examples of inclusions below the surface and casting porosities. Figure 7b is a zoomed-in view of Figure 7a. Figure 7b shows an example of an embedding below the mold surface that is 5.44 mm long. The casting porosities are also indicated, for example, the porosity diameter is indicated to be 0.99 mm.
[025] Figure 8 shows a schematic of the mold with the face coating. Figure 8a shows the mold with the face coating
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8/42 intrinsic which is approximately 100 microns thick. The schematic shows the intrinsic face coating with the mold cavity and the calcium aluminate mold positions also indicated. Figure 8b shows the mold with the extrinsic face coating that is approximately 100 microns thick. The schematic shows the extrinsic face coating with the mold cavity and the calcium aluminate mold positions also indicated.
[026] Figure 9 shows a flow chart, according to aspects of the invention, which illustrates the steps of a method to detect ceramic inclusions below the surface in a titanium or titanium alloy smelter.
Description of Embodiments of the Invention [027] Embodiments of the present invention provide a mold and method for making castings of titanium aluminide and titanium aluminide alloy of high structural integrity, providing for an easy ability to detect inclusions, for example for example, inclusions below surface and / or on surface, which may be present on the outer surface of the foundry or below it. These inclusions can be generated from the molten metal, from the mold making process and / or from the casting process, for example, during an investment casting. In one aspect, a surface zone can form during a casting as a brittle, hard layer known as the "alpha phase" in the art, which can contain unwanted inclusions. The thickness of this layer is usually approximately 0.03 mm [mm].
[028] The manufacture of airplane frame components based on titanium through an investment casting of titanium and its alloys in investment casing molds poses problems from the point of view that the foundries must be cast in almost final form (shape almost final). That is, the components can be fused up to substantially the
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9/42 desired final dimensions of the component, and require little or no treatment or final machining. For example, some foundries may require only a chemical milling operation in order to remove any alpha phase present in the foundry. However, any ceramic inclusions below the surface located below the alpha phase in the smelter are typically not removed through chemical milling. These inclusions below the surface are not visible by visual inspection of the casting, even after chemical milling, and remain in the casting below the alpha phase layer. These inclusions can be formed due to the reaction between the mold face coating and any reactive metal in the molding medium, for example, reactive titanium aluminide.
[029] The present invention provides a new approach to fusing titanium and titanium aluminide components into almost final form, such as turbine blades or airfoils. The embodiments of the present invention provide material compositions for investment casting molds and casting methods that can provide improved components of titanium and titanium alloy, for example, for use in the aerospace industry. In some respects, the mold composition provides a mold that can contain phases that provide an improved mold hardness during a mold creation and / or an increased resistance to reaction with the molten metal during a casting. Molds according to aspects of the invention may be able to melt at high pressure, which is desirable for casting methods in almost final form. A mold composition, for example, which contains particles of calcium aluminate cement and alumina, and preferred constituent phases, has been identified for providing foundries with improved properties.
[030] In one aspect, the constituent phases of the mold comprise calcium monoaluminate (CaA2O4). The present inventors
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10/42 found that calcium monoaluminate is highly desirable for at least two reasons. First, it is understood by the inventors that calcium monoaluminate is believed to promote a hydraulic bond formation between cement particles during the early stages of mold creation, and this hydraulic bond is believed to provide a mold hardness during a construction of mold. Second, it is understood by the inventors that calcium monoaluminate experiences a very low rate of reaction with titanium alloys and titanium aluminide. In a certain embodiment, calcium monoaluminate is provided for the mold composition of the present invention, for example, investment molds, in the form of calcium aluminate cement. In one aspect, the mold composition comprises a mixture of calcium aluminate cement and alumina, i.e., aluminum oxide.
[031] In one aspect of the invention, the mold composition provides a minimal reaction with the alloy during a casting, and the mold provides castings with the required component properties. The external properties of the foundry include features such as shape, geometry and surface finish. The internal properties of the foundry include mechanical properties, microstructure, defects (such as pores and inclusions) below a specified size and within allowable limits.
[032] The mold composition of one aspect of the present invention provides for a low cost casting of titanium aluminide turbine blades (TiAI), for example, low pressure TiAI turbine blades. The mold composition can provide the ability to cast parts in near-final shape that require less machining and / or treatment than parts made using conventional casing molds and gravity casting. As used in this document, the expression “almost final form” implies that the initial production of an article is close to the final (liquid) format of the article, reducing the need for additional treatment, as
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11/42 as extensive machining and surface finish. As used herein, the term “turbine blade” refers to both steam turbine blades and gas turbine blades.
[033] Consequently, the present inventors address the challenges of producing a mold, for example, an investment mold, which does not react significantly with titanium alloys and titanium aluminide. In addition, according to some aspects of the invention, the hardness and stability of the mold allows for high pressure casting approaches, such as centrifugal castings. One of the technical advantages of aspects of this invention is that, in one aspect, the invention can improve from a final foundry that can be generated, for example, from investment molds of calcium aluminate cement and alumina. The higher the hardness, for example, the greater the hardness against fatigue, allows lighter components to be manufactured. In addition, components that have greater fatigue hardness can last longer and thus have lower life cycle costs.
Casting Mold Composition [034] Aspects of the present invention provide a material composition for investment casting molds that can provide enhanced components of titanium and titanium alloys. In one aspect of the present invention, calcium monoaluminate can be provided in the form of calcium aluminate cement. The calcium aluminate cement can be called a cement or a binder. In certain embodiments, calcium aluminate cement is mixed with alumina particulates in order to provide a meltable investment mold mixture. The calcium aluminate cement can typically be greater than about 30% by volume in the meltable mold mixture. In certain embodiments, calcium aluminate cement is between about 30% and about 60% in
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12/42 volume in the die-cast mold mixture. The use of more than 30% by volume of calcium aluminate cement in the meltable mold mixture (foundry mold composition) is a feature of the present invention. The selection of the appropriate chemistry of calcium aluminate cement and the formulation of alumina are factors in the performance of the mold. In one aspect, a sufficient amount of calcium oxide can be provided in the mold composition in order to minimize a reaction with the titanium alloy.
[035] In one aspect, the mold composition, for example, the investment mold composition, may comprise a multi-phase mixture of calcium aluminate and alumina cement particles. The calcium aluminate cement can act as a binder, for example, the calcium aluminate cement binder can provide the backbone main structure of the mold structure. The calcium aluminate cement can comprise a continuous phase in the mold and provides hardness during curing and casting. The mold composition can consist of calcium aluminate cement and alumina, i.e., calcium aluminate cement and alumina can substantially comprise the only components of the mold composition, with little or no other components. In one embodiment, the present invention comprises an article containing a titanium die-casting composition comprising calcium aluminate. In another embodiment, the foundry mold composition further comprises oxide particles, for example, hollow oxide particles. According to aspects of the invention, the oxide particles can be aluminum oxide particles, magnesium oxide particles, calcium oxide particles, zirconium oxide particles, titanium oxide particles and / or silica oxide particles , or combinations thereof.
[036] The foundry mold composition may additionally include aluminum oxide, for example, in the form of hollow particles, ie
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13/42 particles having a hollow core or a substantially hollow core substantially surrounded by an oxide. Such hollow aluminum oxide particles may comprise about 99% aluminum oxide and be about 0.5 millimeter [mm] or less in external dimension, such as width or diameter. In certain embodiments, the hollow oxide particles may comprise hollow spheres of alumina. Hollow alumina spheres can be incorporated into the casting mold composition, and hollow spheres can have a range of geometries, such as round particles or irregular aggregates. In certain embodiments, alumina can include both round particles and hollow spheres. In one aspect, it has been found that these geometries increase the fluidity of the investment mold mixture. The improved fluidity can typically improve the fidelity and surface finish or the accuracy of the surface features of the final cast produced from the mold.
[037] Aluminum oxide comprises particles in the outer dimension range of about 10 microns to about 10,000 microns. In certain embodiments, aluminum oxide comprises particles that are less than about 500 microns in external dimension, for example, diameter or width. Aluminum oxide can comprise from about 0.5% by weight to about 80% by weight of the foundry mold composition. Alternatively, aluminum oxide comprises from about 40% by weight to about 60% by weight of the foundry mold composition.
[038] In one embodiment, the foundry mold composition additionally comprises calcium oxide. The calcium oxide can have more than about 15% by weight and less than about 50% by weight of the foundry mold composition. The final mold can usually have a density of less than 2 grams / cubic centimeter and a hardness of more than 3.44 MPa (500 pounds per square inch [si]). In one embodiment, calcium oxide is more than about 30% by weight and less than about
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14/42 of 50% by weight of the foundry mold composition. Alternatively, calcium oxide has more than about 25% by weight and less than about 35% by weight of the foundry mold composition.
[039] In a specific embodiment, the casting mold composition of the present invention comprises a calcium aluminate cement. Calcium aluminate cement includes at least three phases or components that comprise calcium and aluminum: calcium monoaluminate (CaAhOQ, calcium dialuminate (CaAUO ) And mayanite (Cai2Ali4O33). The volume fraction of calcium monoaluminate can vary from 0 , 05 to 0.95, the volume fraction of calcium dialuminate can vary from 0.05 to 0.80, and the volume fraction of mayanite can vary from 0.01 to 0.30 In another example, the fraction of calcium monoaluminate comprises a volume fraction of about 0.1 to about 0.8; calcium dialuminate comprises a volume fraction of about 0.1 to about 0.6; and mayonnaise comprises a volume fraction of about 0.01 to about 0.2. The volume fraction of calcium monoaluminate in calcium aluminate cement can be more than about 0.5, and the volume fraction of mayanite in the calcium aluminate cement can be less than about 0.15. In another embodiment, calcium aluminate cement has more than 30% by weight of the foundry mold composition.
[040] In one embodiment, calcium aluminate cement has a particle size of about 50 microns or less. A particle size of less than 50 microns is preferred for three reasons: first, the fine particle size is believed to promote the formation of hydraulic bonds during mixing and mold curing; second, it is understood that the fine particle size promotes sintering between particles during a fire discharge, and this can increase the mold hardness; and third, the fine particle size is believed to enhance the surface finish of the molded article. Calcium aluminate cement can be
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15/42 provided as a powder, and can be used either in its intrinsic powder form, or in an agglomerated form, such as spray-dried agglomerates. Calcium aluminate cement can also be pre-mixed with alumina on a fine scale (for example, less than 10 microns in size). Fine-scale alumina is believed to provide an increase in hardness due to sintering during a high temperature fire discharge. In certain cases, a large-scale alumina (that is, greater than 10 microns in size) can also be added with or without the fine-scale alumina.
Composition of Calcium Aluminate Cement [041] The calcium aluminate cement used in aspects of the invention normally comprises three phases or components of calcium and aluminum: calcium monoaluminate (CaAhOQ, calcium dialuminate (CaAUO ) And mayanite (Cai2Ali4O33) Calcium monoaluminate is a hydraulic mineral present in calcium alumina cement. The hydration of calcium monoaluminate contributes to the high early hardness of the investment mold. Mayanite is desirable in cement because it provides hardness during early stages of mold curing due to the rapid formation of hydraulic connections, however, Mayanite is normally removed during a heat treatment of the mold prior to casting.
[042] In one aspect, the initial calcium aluminate cement formulation is usually not in thermodynamic equilibrium after a fire discharge in the cement-making furnace. However, after a mold creation and a high temperature fire discharge, the mold composition moves towards a thermodynamically stable configuration, and this stability is advantageous for the subsequent casting process. In one embodiment, the volume fraction of calcium monoaluminate in cement is greater than 0.5, and the volume fraction of mayanite is less than 0.15. Mayanite is incorporated into the mold by the fact that the
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16/42 it is a quick-adjusting calcium aluminate and it is believed that it endows the hardness cement during the early stages of cure. A cure can be carried out at low temperatures, for example, temperatures between 15 degrees Celsius and 40 degrees Celsius due to the fact that the evanescent wax model is temperature sensitive and loses its shape and its properties in a thermal exposure above about 35 degrees C. It is preferable to cure the mold at temperatures below 30 degrees C.
[043] Calcium aluminate cement can normally be produced by mixing high purity alumina with calcium oxide or high purity calcium carbonate; the mixture of compounds is usually heated to a high temperature, for example, temperatures between 1,000 and 1,500 degrees C in a furnace or an oven and allowed to react.
[044] The resulting product, known in the art as a cement slag, which is produced in the oven is then crushed, crushed and sieved in order to produce a calcium aluminate cement of the preferred particle size. In addition, calcium aluminate cement is designed and processed to have a minimum amount of impurities, such as minimal amounts of silica, sodium and other alkaline base, and iron oxide. In one aspect, the target level for calcium aluminate cement is that the sum of Na2O, S1O2, Fe2O3 and T1O2 is less than about 2 weight percent. In one embodiment, the sum of Na2O, S1O2, Fe2Ü3 and T1O2 is less than about 0.05 weight percent.
[045] In one aspect of the invention, a calcium aluminate cement is provided with crude alumina concentrations above 35% by weight of alumina (AI2O3) and less than 65% by weight of calcium oxide. The maximum alumina concentration of the cement can be about 85% (for example, about 15% CaO). In one embodiment, the calcium aluminate cement is of high purity and contains up to 70% alumina. The volume fraction
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17/42 of calcium monoaluminate can be maximized in the mold subjected to a fire discharge before casting. A minimum amount of calcium oxide may be required to minimize a reaction between the casting alloy and the mold. If there is more than 50% calcium oxide in the cement, this can lead to phases such as mayanite and calcium trialuminate, and they do not perform like calcium monoaluminate during a casting. The preferred range for calcium oxide is less than about 50% and greater than about 15% by weight.
[046] As noted above, the three phases in the cement / calcium aluminate binder in the mold are calcium monoaluminate (CaAhOQ, calcium dialuminate (CaAUOz) and mayanite (Cai2Ali4O33). Calcium monoaluminate in cement / binder has three advantages in relation to other phases of calcium aluminate: 1) Calcium monoaluminate is incorporated into the mold due to the fact that it has a quick adjustment response (although not as fast as mayanite) and it is believed that the same endowment hardness mold during the early stages of cure. The rapid generation of a mold hardness provides dimensional stability of the casting mold, and this feature improves the dimensional consistency of the final cast component. 2) Calcium monoaluminate is chemically very stable in relation to the titanium and titanium aluminide alloys that are fused. Calcium monoaluminate is preferred over calcium dialuminate, and other phases of calcium aluminate with higher alumina activity; these phases are more reactive with titanium alloys and titanium aluminide which are fused. 3) Calcium monoaluminate and calcium dialuminate are phases of low expansion and are understood to prevent the formation of high levels of stress in the mold during curing, wax removal and subsequent casting. The thermal expansion behavior of calcium monoaluminate corresponds approximately to that of alumina.
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Foundry Mold Composition with Enhanced Detection Capability [047] There is a small difference in the X-ray density of the mold materials (calcium aluminate cement and alumina) and titanium, and inclusions that originate from the mold are therefore difficult to to detect. In order to address this limitation, species can be added to the ceramic investment mix in order to improve an X-ray detection capability of inclusions.
[048] One aspect of the invention is a mold composition for melting an article containing titanium, comprising: a calcium aluminate cement comprising calcium monoaluminate, calcium dialuminate and mayanite; and a neutron or X-ray detectable element. Another aspect of the present invention is an article that contains a titanium casting molding composition, comprising calcium aluminate; and a neutron or X-ray detectable element. In one embodiment, the calcium aluminate cement forms an intrinsic face coating of less than about 100 microns when the mold composition forms a mold. In one embodiment, the elements detectable by neutron ray or X-ray are mixed within the mold. In another embodiment, the elements detectable by neutron ray or X-ray are mixed within the mold and become part of the intrinsic face coating.
[049] There are many different methods in which elements detectable by X-ray or neutron ray can be mixed with the mold mixture. For example, the element can be added as a liquid such as nitrate at any stage of the mold mixing process. The element can also be added as an oxide, as described in this document. In one embodiment, the element is combined as an oxide with alumina in a joined form, such as an erbium aluminum grenade or a dysprosium aluminum grenade, before generating the mixture of
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19/42 mold. It will be understood by a technician on the subject of creating a ceramic mold that different approaches can be employed in order to introduce the elements detectable by neutron ray or X-ray into the mold. In one embodiment, the mold composition does not have an intrinsic face coating.
[050] The mold composition may additionally comprise oxide particles. The oxide particles comprise particles of at least one of aluminum oxide, magnesium oxide, calcium oxide, zirconium oxide and titanium oxide. In a specific embodiment, the oxide particles are aluminum oxide particles. The cast article containing titanium can be an engine, a turbine or a turbine blade.
[051] Since there is only a small difference between the X-ray density of the mold materials (calcium aluminate cement and alumina) and the titanium X-ray density, the inclusions that originate from the mold are difficult to detect. Here, the inventors added certain X-ray detectable elements to their investment mix in order to improve the ability to detect inclusions below the surface. Consequently, an aspect of the present invention is a method for detecting ceramic inclusions below the surface in a titanium or titanium alloy foundry, which comprises: combining calcium aluminate, a radiographically denser element than calcium aluminate and a liquid to form a slurry; forming a mold that has the calcium aluminate and the radiographically dense element from the slurry; introducing a metal containing titanium aluminide into the mold that bears a dense element radiographically; solidifying said metal containing titanium aluminide in order to form an article in the mold; removing the solidified metal article containing titanium aluminide from said mold; subject the solidified article containing titanium aluminide to radiographic inspection
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20/42 in order to provide an x-ray; and examining said radiography for the presence of the radiographically dense element on or in the article. In one embodiment, the method comprises minimizing the presence of mold material inclusions in cast articles containing titanium aluminide.
[052] The combining step additionally comprises combining oxide particles with the slurry. A liquid, such as water, for example, deionized water, can be added to the slurry in order to adjust a slurry viscosity. Any viscosity measurement protocol or instrument can be used. Typically, the viscosity is adjusted to be between 8 to 20 seconds, preferably 9 to 12 seconds, for the cement slurry mixture as determined using the Zahn cup viscosity measurement technique; this technique is well known to a person skilled in the art. The amount of water present in the slurry is limited so as not to decrease the green hardness or subject to fire discharge from the casing mold. In certain embodiments, the radiographically dense element is radiographically more dense than the oxide particles, for example, the radiographically dense element is more radiographically dense than calcium oxide. In certain embodiments, the oxide particles comprise hollow oxide particles, for example, hollow aluminum oxide particles.
[053] One of the advantages of the present invention is that castings can be produced in order to provide an improved detection capacity of any inclusions below surface and / or surface on, near and / or below the surface of the casting that are not usually detectable through visual inspection. For example, the inclusions that can be located below an alpha phase layer
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21/42 of a titanium-based foundry and which are not removed by a chemical post-casting milling operation or other surface treatments can be detected through aspects of the invention. In addition, conventional chemical milling regimes can also be used to remove the alpha phase from the foundry because the practice of the invention does not promote additional alpha phase formation in titanium-based foundries.
[054] One aspect of the present invention provides a composition for casting materials, for example, investment casting molds, which can provide enhanced X-ray or neutron ray inspection capabilities for inclusions that may occur undesirably in the casting, for example, of the casting mold. In one embodiment, this is achieved by adding a radiographically denser element than the casting mold composition, for example, radiographically denser than calcium aluminate. In one aspect, the present invention is a mold composition for casting articles containing titanium, comprising: calcium aluminate; and a neutron or X-ray detectable element. The cast article containing titanium may be a titanium aluminide engine component, a titanium aluminide turbine or a titanium aluminide turbine blade. In one embodiment, the neutron or X-ray detectable element that can be used includes at least one of iterbium, hafnium, gadolinium, tungsten, thorium, uranium, yttrium, dysprosium, erbium, cerium and compositions thereof. These elements are used in some cases because they are radiographically denser than calcium aluminate.
[055] One aspect of the present invention is a mold composition comprising a calcium aluminate cement that
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22/42 comprises calcium monoaluminate, calcium dialuminate and mayanite; and at least one element denser radiographically than calcium aluminate cement. Another aspect of the present invention is a mold composition that comprises calcium aluminate and at least one radiographically denser element than calcium aluminate. Investment mixes of calcium aluminate and alumina cement bearing erbium, dysprosium and / or gadolinium have the advantage of the relatively high X-ray detection capacity of erbium, dysprosium and gadolinium compared to other elements. An additional advantage is that erbium, dysprosium and gadolinium are also resistant to a reaction with titanium and titanium alloys melted during a casting. Investment mixtures that carry erbium, dysprosium and / or gadolinium are not radioactive compared to ThO2 and other mold compositions that carry radioactivity and are therefore preferred in some modalities.
[056] The mold formulation may not form an intrinsic face coating, such as yttrium, when formed in a mold, but the formulation may be a two-phase homologous composition of calcium alumina and alumina. During an investment mix, pouring and curing, the mold forms an intrinsic calcium aluminate face coating on the mold. According to one aspect of the invention, the intrinsic face coating (usually less than 100 microns thick) of calcium aluminate in the mold also contains particles of radiographically dense elements, for example, mixed erbium and / or dysprosium and / or gadolinium in the mold material. Additions containing erbium, dysprosium and gadolinium to the investment mixture are used for the molds to create castings of titanium aluminide and titanium aluminide alloy because of the fact that erbium, dysprosium and gadolinium exhibit a higher X-ray density
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23/42 than that of the ceramic components. Part of the radiographically dense elements, for example, erbium, dysprosium and gadolinium, also exhibit acceptable resistance to a reaction with titanium aluminide and titanium aluminide alloys melted during the casting operation.
The Mold, Methods for Casting and Detecting Inclusions Below
Surface [057] An investment mold is formed by formulating the investment mixture of the ceramic components, and pouring the mixture into a container containing an evanescent model. The investment mold formed in the model is allowed to cure completely in order to form a so-called green mold. Usually, a cure of the green mold is carried out in 1 hour to 48 hours. Subsequently, the evanescent model is selectively removed from the green mold by undergoing a known fusion, dissolution, ignition or other model removal technique. Normal methods for removing a wax model include removal of wax from the oven (less than 150 degrees C), removal of wax from the furnace (greater than 150 degrees C), removal of wax by steam autoclave and a removal of wax by microwave.
[058] To cast titanium alloys, titanium aluminide and their alloys, the green mold is then subjected to a fire discharge at a temperature above 600 degrees C, preferably 700 to 1,400 degrees C, for a period of time in excess 1 hour, preferably 2 to 6 hours, in order to develop a mold hardness to melt and to remove any unwanted residual impurities in the mold, such as metallic species (Fe, Ni, Cr), species that contain carbon. The atmosphere of a mold fire discharge is usually ambient air, although an atmosphere of inert gas or reducing gas can be used.
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24/42 [059] The fire discharge process also removes water from the mold and converts the mayonnaise into calcium aluminate. Another purpose of the mold fire discharge procedure is to minimize any free silica left in the mold before casting. Other purposes are to remove water, increase hardness at high temperature and increase the amount of calcium monoaluminate and calcium dialuminate.
[060] The mold is heated from an ambient temperature to the final fire discharge temperature, specifically the thermal history and the humidity profile are controlled. The heating rate for the fire discharge temperature, and the cooling rate after a fire discharge are normally regulated or controlled. If the mold is heated too quickly, it can crack internally or externally, or both; a crack in the mold before casting is highly undesirable. In addition, if the mold is heated too quickly, the mold may crack and break into pieces. This can lead to unwanted inclusions in the final casting, and a poor surface finish, even if there are no inclusions. Similarly, if the mold is cooled quickly after reaching the maximum temperature, the mold can also crack internally or externally, or both.
[061] The mold composition described in the present invention is particularly suitable for titanium and titanium aluminide alloys. The mold composition after a fire discharge and before a casting can influence the mold properties, particularly in relation to the constituent phases. In one embodiment, for casting purposes, a high volume fraction of calcium monoaluminate in the mold is preferred, for example, a volume fraction of 0.3 to 0.8. In addition, for casting purposes, it is desirable to minimize the volume fraction of Mayanite, for example, with the use of a volume fraction of 0.01 to 0.2, because the Mayanite is sensitive to water and can provide problems with water release and generation
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25/42 gas during a casting. After a fire discharge, the mold may also contain small volume fractions of aluminosilicates and calcium aluminosilicates. The sum of the volume fractions of aluminosilicate and calcium aluminosilicate can normally be kept at less than 5% in order to minimize a reaction of the mold with the melt.
[062] In certain embodiments, the casting mold composition of the present invention comprises an investment casting mold composition. The investment casting mold composition comprises an almost final shape, a metal containing titanium, an investment casting mold composition. In one embodiment, the investment casting mold composition comprises an investment casting mold composition for melting titanium aluminide articles in near-final form. Titanium aluminide articles in near final shape comprise, for example, titanium aluminide turbine blades in near final shape.
[063] The selection of the correct calcium aluminate cement chemistry and alumina formulation are factors in the performance of the mold during a casting. In terms of calcium aluminate cement, it may be necessary to minimize the amount of free calcium oxide in order to minimize a reaction with the titanium alloy. If the calcium oxide concentration in the cement is less than 15% by weight, the alloy reacts with the mold because the concentration of alumina is very high, and the reaction generates undesirable levels of oxygen concentration in the melt, bubbles of gas and a poor surface finish on the molten component. If the calcium oxide concentration in the cement is greater than 50% by weight, the mold may be sensitive to a choice of water and carbon dioxide from the environment. Therefore, the calcium oxide concentration in the investment mold can normally be kept below 50%. In one embodiment, concentration
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26/42 calcium oxide is between 15% and 40% by weight. Alternatively, the calcium oxide concentration is between 25% and 35% by weight.
[064] Carbon dioxide can lead to the formation of calcium carbonate in the mold during processing and before casting, and calcium carbonate is unstable during the casting operation. In this way, water and carbon dioxide in the mold can lead to poor casting quality. If the level of water absorbed is too high, for example, greater than 0.05 weight percent, when the molten metal enters the mold during a casting, the water is released and it can react with the alloy. This leads to poor surface finish, gas bubbles in the foundry, high oxygen concentration and poor mechanical properties. Similarly, if the level of carbon dioxide is too high, calcium carbonate can form in the mold and when molten metal enters the mold during a smelting, calcium carbonate can decompose a carbon dioxide in generation, which can react with the alloy. The resulting calcium carbonate is less than 1 percent by weight of the mold.
[065] Before casting a molten metal or an alloy, the investment mold is usually preheated to a mold casting temperature that is dependent on the geometry or the particular component alloy to be cast. For example, a normal mold preheat temperature is 600 degrees C. Typically, the mold temperature range is 450 degrees C to 1,200 degrees C; the preferred temperature range is 450 degrees C to 750 degrees C, and in certain cases is 500 degrees C to 650 degrees C.
[066] According to one aspect, the molten metal or alloy is poured into the mold using conventional techniques that can include gravity, counter gravity, pressure, centrifuge and other casting techniques known to a person skilled in the art. Vacuum or inert gas atmospheres can be used. For thin-walled geometries formatted
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27/42 complex, techniques that use high pressure are preferred. After the solidified titanium aluminide or the alloy casting is normally cooled to less than 650 degrees, for example, to an ambient temperature, it is removed from the mold and finished using conventional techniques, such as abrasive blasting, blasting by water jet and polishing.
[067] One aspect of the present invention is a method for detecting inclusions of ceramic below the surface in a titanium or titanium alloy smelter, comprising: combining calcium aluminate, at least one radiographically denser element than aluminum aluminate. calcium, and a liquid to form a slurry; forming a mold that has the calcium aluminate and the radiographically dense element from the slurry; introducing a metal containing titanium aluminide into the mold that bears a dense element radiographically; solidifying said metal containing titanium aluminide in order to form an article in the mold; removing the solidified metal article containing titanium aluminide from said mold; subject the solidified article containing titanium aluminide to a radiographic inspection in order to provide a radiography; and examining said radiography for the presence of the radiographically dense element on or in the article. In one embodiment, the method comprises minimizing the presence of mold material inclusions in cast articles containing titanium aluminide.
[068] Between removing said evanescent model from the mold and preheating the mold to a mold casting temperature, the mold is first heated to a temperature of about 450 degrees C to about 900 degrees C and then cooled to room temperature . In one embodiment, the curing step is conducted at temperatures below about 30 degrees C for between one hour to 48 hours. Removing the evanescent model includes the melting, dissolving, igniting, wax removal by oven, wax removal by furnace, wax removal by steam autoclave, or removal
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28/42 microwave wax. In one embodiment, after removing the titanium or titanium alloy from the mold, the casting can be finished with abrasive blasting, water blasting or polishing. After the solidified casting is removed from the mold, it is inspected by X-ray or neutron radiography.
[069] For the present invention, the solidified casting is subjected to a surface inspection and an X-ray radiography after a casting and finishing in order to detect any inclusion particles below the surface at any location within the casting. An X-ray radiography is used to find inclusions that are not detectable through visual inspection of the casting's outer surface. The titanium aluminide smelter is subjected to an X-ray radiography (film or digital) using conventional X-ray equipment to provide an X-ray radiography that is then inspected or analyzed to determine if any Below-surface inclusions are present within the titanium aluminide smelter.
[070] Below-surface inclusions can originate from the investment mold face coating or the mold face coating as a result of mold erosion during a mold filling, a reaction between the reactive molten metal and the face coating mold and / or mechanical splitting into pieces as a result of thermal shock from the mold. When an inclusion or inclusions below the surface are found using X-ray methods, the smelter may be subjected to repair operations by sharpening or welding to remove and replace sufficient material to remove objectionable inclusions; alternatively the casting can be scraped if the inclusion or inclusions are larger than a specified size for the required mechanical integrity of the casting.
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29/42 [071] The solidified casting is normally subjected to a surface inspection and an X-ray radiography after a casting and finishing in order to detect any ceramic inclusion particles, for example, inclusion particles below the surface, anywhere within the foundry. Investment mixes of calcium aluminate cement and alumina are used which contain erbium, dysprosium and gadolinium. The investment mixture of calcium aluminate cement and alumina that has an erbium port can be selected from erbic powder (erbium oxide) bonded, calcined or sintered in bonded form or in another form. The bonded erbium powder is preferred as the erbium slurry component since it is more dense and resistant to a chemical reaction with a melted material of titanium aluminide or titanium aluminide alloy than calcined erbium powder or sintered. A joined erbic powder can be added to the investment mold mixture during mixing, at any stage. In one embodiment, the joined erbia powder is added together with the calcium aluminate cement. A united erbia powder particularly useful in the practice of the invention is available as Auercoat 4/3 from Treibacher Auermet GmbH, A9330 Treibach-Althofen, Austria, in -325 mesh powder particle size (less than 44 microns). A calcined erbia powder useful in the practice of the invention is available as Auercoat 4/4 also from Treibacher Auermet GmbH in the particle size of -325 mesh (less than 44 microns). Mesh size refers to the U.S. standard screening system
[072] In one embodiment, the method additionally comprises the step of removing the dense element radiographically from the article. This removal of the radiographically dense element from the article can be achieved through one or more stages of machining, grinding, polishing or welding. Chemical milling can also be used to remove the radiographically dense element from the article.
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30/42 [073] Since there is a risk that inclusions below the surface become embedded in the molten component and thereby reduce the hardness and load carrying capacity of the final foundry, the present invention is directed towards the detection and elimination these inclusions below the foundries' surface, in order to maximize the mechanical properties and performance of the foundries. The present invention provides methods for improving the structural integrity of foundries by increasing the likelihood of detecting inclusions that can be generated from investment molds of calcium aluminate cement and alumina during a titanium aluminide smelter.
[074] The present invention also allows for the detection of smaller inclusions because of the greater X-ray contrast. The greater probability of detecting inclusions and the greater ability to detect smaller inclusions with modern digital X-ray methods improves hardness and strength. fatigue hardness of castings of titanium alloys and titanium aluminide alloys.
[075] The described mold compositions provide a small amount of a material that has a high neutron absorption cross-section. In one aspect, a neutron radiograph is prepared from the molten article. Since the cast titanium alloy article can be substantially transparent to neutrons, the mold material will normally show up differently on the resulting neutron radiography.
[076] In one respect, neutron exposure is believed to result in "neutron activation" of the dense element radiographically. Neutron activation involves the interaction of neutron radiation with the radiographically dense element of the smelter to effect the formation of radioactive isotopes from the radiographically dense elements of the mold composition. The radioactive isotopes can then be detectable through
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31/42 conventional radioactive detection devices to count any radiographically dense element isotopes present in the cast article.
[077] A neutron thermal beam can be obtained from numerous sources, including a nuclear reactor, a subcritical set, a radioactive neutron source or an accelerator. Images produced using an N-ray can be recorded on a film, such as with an X-ray. This is usually achieved by placing a part to be imaged in a neutron beam and then recording the image on a film for each angle in the which image is desired. N-ray images can also be taken in real time with modern digital detection equipment.
[078] The N ray uses neutrons as penetrating radiation to imagine inclusions. All neutron energies, for example, fast, epidermal, thermal and cold neutron can be used for Ν ray imaging. N-ray imaging is a process by which an intensity beam modulation of an object is used to identify inclusions and defects. Components required for N-ray imaging include a fast neutron source, a moderator, a gamma filter, a collimator, a conversion screen, a film image recorder or other imaging system, a cassette and shielding systems adequate biological and interlocking.
[079] In one aspect, the method currently taught can be used in titanium aluminide castings when there is an addition to the mold material which is a strong neutron absorber. Neutron absorption additives are suitable because they have the desired high neutron absorption cross-section. Since neutron radiographs are generally produced using neutrons that have levels of thermal or resonant energy, it is generally preferred that the neutron-absorbing material has a high-absorption cross-section for
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32/42 thermal neutrons. Exemplary materials that have high thermal absorption cross-sections of neutron that are compatible with the titanium aluminide mold of the present invention include erbium, dysprosium, gadolinium and mixtures thereof.
[080] In general, the greater the cross-section of neutron absorption of the additive, the smaller the amount required to give the desired imaging characteristics. Generally, less than 10 weight percent is used. For example, the X-ray or neutron ray detectable component is in the range of about 0.5 to about 6 weight percent in the mold composition. Good results can be obtained with erbium, dysprosium or gadolinium oxide in the range of about 1 to about 4 weight percent of the core material. Gadolinium has a very high neutron absorption cross-section and produces excellent images with small amounts in the mold. In one embodiment, the solutions used to improve an N-ray and X-ray contrast comprise nitrate, halo, sulfate and perchlorate salts of the elements for N-ray and X-ray improvement.
[081] In one aspect, the selection of suitable mold additions for X-ray contrast enhancement and detection depends on the difference between the density of the imaging agent and that of the titanium alloy casting. The selection of mold additions suitable for N-ray imaging of inclusions is determined by the coefficient of linear attenuation or the thermal cross-section of the neutron of the addition of the image in relation to that of the fused titanium part, and throughout the entire process. cross-section of the foundry.
[082] In one aspect of the present invention, the inventors selected N-ray and X-ray contrast enhancement elements to add to the calcium aluminate investment mold based on factors including: the element's oxide stability against metal in
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33/42 metal (low reaction rate), X-ray density compared to titanium, and N-ray moderation compared to titanium, and availability / cost. With these criteria in mind, three species were identified: erbia, dysprosia and gadolinium. Other elements of contrast enhancement such as neodymium, samarium, europium, holmium, ytterbium and lutetium were considered based on the above criteria, however, they were not thought to provide the same results in this application as when gadolinium, erbium and dysprosium are used. In one embodiment, gadolinium, erbia and dysprosia are preferred for detecting inclusions that may come from calcium aluminate molds when melting titanium or titanium alloy.
[083] Regarding an X-ray detection of inclusions, the primary factors that affect a detection capability include (1) the difference between the density of the titanium alloy compared to the density of the inclusion, (2) the size, the thickness, shape and orientation of the inclusion, and (3) the thickness of the cross section of the cast titanium alloy component. If the difference between the density of the molten material and the inclusion is small (such as less than about 0.5 g / cc), there may not be enough image contrast to detect the inclusion by X-ray. Under these circumstances, an N ray is employed, provided the appropriate element is added for an improvement of contrast by N ray.
[084] In one aspect of the present invention, the selection of imaging agents suitable for X-ray detection depends on the difference between the density of the imaging agent and that of the metal or alloy of the foundry. In one example, the selection of suitable imaging agents for N-ray imaging of inclusions is determined through the linear attenuation coefficient or the cross-section of neutron absorption of the material that is used as an imaging agent in relation to the same. metal or alloy that is cast. THE
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34/42 difference between the linear attenuation coefficient or the neutron absorption cross section of the mold and that of the casting needs to be sufficient, so that any mold inclusions can be imaged throughout the cross section of the article.
[085] Gadolinium is a preferred addition to the mold for imaging using N-ray detection of inclusions in titanium or titanium alloy castings. Gadolinium has a very high cross-section of neutron absorption. Specifically, the gadolinium neutron absorption cross-section is 259,000 barns, while the titanium neutron absorption cross-section is about 6.1 barns. The cross-section of neutron absorption of other elements includes, dysprosium (2,840 barns), erbium (659 barns), yttrium (1,3 barn), calcium (0.4 barn), aluminum (0,2 barn). Thus, the capacity for N-ray imaging of inclusions containing calcium and containing aluminum, for example, is very low, (for additional information, see the National Standards Institute and the website of the Technology Center for Research on Neutron). Therefore, element selection is a feature of the invention and isotopes of the selected elements can be used.
[086] In one aspect, the addition of gadolinium, dysprosium or erbium can substantially improve the neutron absorption capacity in relation to titanium and therefore the inclusion imaging contrast capacity during an N ray is substantially increased. Gadolinium isotope 157 is believed to have a neutron thermal absorption cross-section of 259,000 barns. The difference between the absorption cross section of titanium neutron or titanium alloys makes gadolinium particularly suitable for N-ray imaging. For metals and / or alloys other than titanium, gadolinium is also a preferred imaging agent, primarily because of the relatively low neutron absorption cut
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Large 35/42 gadolinium.
[087] One of the technical advantages of aspects of the invention is that they improve the structural integrity of castings of an article containing titanium allowing for an improved detection of inclusions that can be generated from investment mixes of calcium aluminate cement and alumina. The invention also allows the detection of smaller inclusions because of the greater X-ray contrast. The greater probability of detecting inclusions and the greater ability to detect smaller inclusions with the most modern digital X-ray methods improves hardness and hardness against fatigue in castings of titanium alloys and titanium aluminide alloys. The higher hardness allows for lighter components, and the higher fatigue hardness provides for components with longer service lives and thus lower life cycle costs. In one embodiment, the component comprises a titanium aluminide turbine blade.
Examples [088] The invention, which has been generally described, can be more readily understood with reference to the following examples, which are included merely for purposes of illustrating certain aspects and certain embodiments of the present invention, and are not intended to limit the invention no way.
Investment Mold Composition and Formulation [089] A calcium aluminate cement was mixed with alumina in order to generate an investment mold mixture, and a range of investment mold chemicals was tested. The investment mixture consisted of calcium aluminate cement with 70% alumina and 30% calcium, particles of alumina, water and colloidal silica.
[090] In a first example, a mixture of normal slurry to make an investment mold consisted of 3,000 grams [g] of
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36/42 calcium aluminate cement, (comprising approximately 10% by weight of mayanite, approximately 70% by weight of calcium monoaluminate and approximately 20% by weight of calcium dialuminate), 1,500 g of alumina particles calcined with a size less than 10 microns, 2,450 g of calcined, high purity alumina particles of a size in the range of 0.5 to 1 mm in diameter, 1,650 g of deionized water and 150 g of colloidal silica.
[091] The normal high purity calcined alumina particle types include bonded, tabular and levigated alumina. Normal suitable colloidal silicas include Remet LP30, Remet SP30, Nalco 1030 and Ludox. The mold produced was used to cast articles containing titanium aluminide such as turbine blades with a good surface finish. The roughness value (Ra) was less than 2.54 micrometers (100 microinches), and with an oxygen content of less than 2,000 parts per million [pm]. This formulation produced a mold that was approximately 120 mm in diameter and 400 mm in length. This formulation produced a mold that had a density of less than 2 grams per cubic centimeter.
[092] The mold mixture was prepared by mixing calcium aluminate cement, water and colloidal silica in a container. A mixture of high shear form was used. If not mixed thoroughly, the cement can become gel. When the cement was in total suspension in the mixture, the fine-scale alumina particles were added.
[093] When the fine-scale alumina particles were completely mixed with the cement, the larger alumina particles (for example, 0.5 to 1.0 mm) were added and mixed with the cement-alumina formulation. The viscosity of the final mixture is another factor, since it must not be too high or too low. Besides that,
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37/42 accelerators and retarders can be used at selected points during the mold creation process steps. A standard individual dispersing alumina with accelerators and retarders includes Almatis ADS-1, ADS-3 and ADW-1.
[094] After mixing, the investment mixture was poured in a controlled manner into a container containing the evanescent wax model. The container provides the external geometry of the mold, and the evanescent model generates the internal geometry. The correct pouring speed is an additional feature, if it is too fast the air can be captured in the mold, if it is too slow a separation of cement and alumina particulate may occur. An adequate pouring speed ranges from about 1 to about 20 liters per minute. In one embodiment, the pouring speed is about 2 to about 6 liters per minute. In a specific embodiment, the pouring speed is about 4 liters per minute.
[095] In a second example, a slurry mix to make an investment mold consisted of 3,000 g of calcium aluminate cement, (which comprises approximately 10% by weight of mayanite, approximately 70% by weight of calcium monoaluminate) and approximately 20% by weight of calcium dialuminate), 1,500 g of calcined alumina particles with a size of less than 10 microns, 2,650 g of high purity calcined alumina bubble of a size in the range of 0.5 to 1 mm in diameter, 1,650 g of deionized water and 150 g of colloidal silica.
[096] Hollow alumina particles provide a mold with a reduced density. The weight fraction of calcium aluminate cement is 42%, and that of alumina is 58%. This formulation produced a mold that was approximately 125 mm in diameter and 400 mm in length. The mold was then cured and subjected to a high fire discharge
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38/42 temperature. The mold produced was used to cast articles containing titanium aluminide such as turbine blades with a good surface finish. The roughness value (Ra) was less than 100 and with an oxygen content of less than 2,000 ppm. This formulation produced a mold that had a density of less than 1.8 grams per cubic centimeter.
[097] In a third example, a mixture of slurry to make an investment mold consisted of 600 g of calcium aluminate cement, (consisting of approximately 10% by weight of mayanite, approximately 70% by weight of monoaluminate). calcium and approximately 20% by weight of calcium dialuminate), 300 g of calcined alumina particles with a size of less than 10 microns, 490 g of high purity calcined alumina bubble in a size range of 0.5 to 1 mm in diameter, 305 g of deionized water and 31 g of colloidal silica. This formulation produced a smaller mold for a smaller component that was approximately 120 mm in diameter and 150 mm in length. The mold was then cured and subjected to a high temperature fire discharge. The mold produced was used to cast articles containing titanium aluminide such as turbine blades with a good surface finish. The roughness value (Ra) was less than 2.54 micrometers (100 microinches) and with an oxygen content of less than 1,600 ppm.
[098] In a fourth example, a mixture of slurry to make an investment mold consisted of 2708 g of calcium aluminate cement, (which comprises approximately 10% by weight of mayanite, approximately 70% by weight of calcium monoaluminate) and approximately 20% by weight of calcium dialuminate), 1,472 g of high purity calcined alumina bubble from a size range of 0.5 to 1 mm in diameter, 1,061 g of deionized water and 196 g of colloidal silica. This formulation produced a smaller mold with a lower alumina content for a
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39/42 minor component. The mold was then cured and subjected to a high temperature fire discharge. The mold produced was used to melt articles containing titanium aluminide such as turbine blades.
[099] Colloidal silica controls the reaction rate of the calcium aluminate phases with water and provides a mold hardness during curing. This rate of reaction of the calcium aluminate phases with water controls the working time of the investment mold mixture during a mold creation. That time was between about 30 seconds and about 10 minutes. If the working time of the investment mold mixture is too short, there is insufficient time to make large molds of complex shaped components. If the working time of the investment mold mixture is too long and the calcium aluminate cement does not cure fast enough, a separation of fine scale cement and large scale alumina can occur and this can lead to a segregated mold in the which formulation varies and the resulting mold properties are not uniform.
[0100] The three phases in calcium aluminate cement comprise calcium monoaluminate (CaAhOQ, calcium dialuminate (CaAUO ) And mayanite (Cai2Ali4O33), and the inventors made this selection in order to achieve many purposes. dissolve or partially dissolve and form a suspension that can withstand all phases of aggregate in the slurry which creates a subsequent investment mold Second, the phases must promote an adjustment or cure of the mold after pouring Third, the phases must provide hardness to the mold during and after a casting. Fourth, the phases must exhibit a minimal reaction with the titanium alloys that are cast in the mold. Fifth, the mold must have a suitable thermal expansion match with the titanium alloy casting in order to minimize thermal stress on the part that is generated during post-solidification cooling.
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40/42 [0101] The X-ray image (Figure 7) shows a fused titanium aluminide paddle that contains an under-surface inclusion of a calcium aluminate mold. This is a very large inclusion (5.44 mm) and can be solved with digital improvement techniques. Smaller low-density inclusions of a calcium aluminate mold are more difficult to resolve. In one aspect of the invention, the inventors used mold additions that increase the X-ray density of the mold in order to improve the ability to detect inclusion.
[0102] It should be understood that the description above is intended to be illustrative and not restrictive. For example, the achievements described above (and / or aspects of them) can be used in combination with each other. In addition, many modifications can be made to adapt a particular material or situation to the teachings of the various achievements without departing from its scope. Although the dimensions and types of materials described in this document are intended to define the parameters of the various modalities, they are by no means limiting and are merely exemplary. Many other achievements will be apparent to those of skill in the art upon review of the above description. The scope of the various achievements must therefore be determined with reference to the attached claims, together with the total scope of equivalents to which such claims are entitled. In the attached claims, the terms "which includes" and "in (a) which" are used as the full English equivalents of the respective terms "which comprises" and "in which". Furthermore, in the following claims, the terms "first", "second" and "third" etc. they are used merely as labels, and are not intended to impose numerical requirements on your objects. Furthermore, the limitations of the following claims are not written in a somewhat more functional format and are not intended to be interpreted based on 35 U.S.C. §
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41/42
112, sixth paragraph, unless and until such claim limitations expressly use the phrase "means to" followed by an empty function statement of additional structure. It should be understood that not necessarily all of the objectives and advantages described above can be achieved in accordance with any particular achievement. Thus, for example, a person skilled in the art will recognize that the systems and techniques described in this document can be incorporated or realized in a way that achieves or optimizes an advantage or group of advantages as taught in this document without necessarily reaching others objectives and other advantages as can be taught or suggested in this document.
[0103] Although the invention has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Instead, the invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent provisions not described so far, but which are commensurate with the spirit and scope of the invention. In addition, although various embodiments of the invention have been described, it should be understood that aspects of the invention may include only part of the described modalities. Consequently, the invention should not be seen as limited by the foregoing description, but is only limited by the scope of the appended claims. All publications, patents and patent applications mentioned in this document are hereby incorporated by reference in their entirety as if each individual publication or patent were specifically and individually indicated to be incorporated by reference. In the event of a conflict, this patent application, including any definitions in this document, will control.
Petition 870180071402, of 08/15/2018, p. 54/59
42/42 [0104] This written description uses examples to reveal the invention, which includes the best way, and also to allow a person skilled in the art to practice the invention, which includes creating and using any devices or systems and executing any built-in methods. The patentable scope of the invention is defined by the claims and may include other examples that occur to a person skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal language of the claims.
Petition 870180071402, of 08/15/2018, p. 55/59
1/3

权利要求:
Claims (2)
[1]
1/10 ο
Q fOZ) σ σ
Csl CN CN
0ovynivy3dW3i ‘Ή
W LU S W
1, characterized by the fact that it additionally comprises oxide particles.
3. MOLD COMPOSITION, according to the claim
2, characterized by the fact that the oxide particles comprise at least one of aluminum oxide particles, magnesium oxide particles, calcium oxide particles, zirconium oxide particles and titanium oxide particles.
4. COMPOSITION, according to claim 1, characterized by the fact that the element detectable by neutron ray or X-ray is in the range of 1 to 4 weight percent in the mold composition.
5. METHOD FOR DETECTING CERAMIC INCLUSIONS, below a surface in a titanium or titanium alloy foundry, characterized by the fact that the method comprises:
combining calcium aluminate, at least one element denser radiographically than calcium aluminate and a liquid to form a slurry;
form a mold that has the calcium aluminate and the element
Petition 870180071402, of 08/15/2018, p. 56/59
2/3 dense radiographically from the slurry, and after a fire discharge, the mold comprises aluminosilicates and calcium aluminosilicates, in which the volume fractions of aluminosilicate and calcium aluminosilicate are less than 5% by weight ;
introducing a metal containing titanium aluminide into the mold that bears a dense element radiographically;
solidifying the metal containing titanium aluminide to form an article in the mold;
removing the solidified metal article containing titanium aluminide from the mold;
subject the solidified article containing titanium aluminide to a radiographic inspection in order to provide a radiography; and examine the radiography for the presence of the dense element radiographically on or in the article.
6. METHOD, according to claim 5, characterized by the fact that it also comprises removing the dense element radiographically from the article.
7. METHOD, according to claim 6, characterized by the fact that removing the dense element radiographically from the article comprises one or more among machining, grinding, polishing or welding.
8. METHOD, according to claim 5, characterized by the fact that the combination also comprises combining oxide particles with the slurry.
9. METHOD according to claim 8, characterized by the fact that the oxide particles comprise at least one of aluminum oxide particles, magnesium oxide particles, calcium oxide particles, zirconium oxide particles and particles of titanium oxide.
10. METHOD, according to claim 8, characterized
Petition 870180071402, of 08/15/2018, p. 57/59
3/3 by the fact that the oxide particles are aluminum oxide particles.
11. METHOD, according to claim 8, characterized by the fact that the element is more dense radiographically than the oxide particles.
12. METHOD according to claim 8, characterized in that the oxide particles comprise hollow oxide particles.
13. METHOD according to claim 12, characterized in that the hollow oxide particles comprise hollow aluminum oxide particles.
14. METHOD, according to claim 5, characterized by the fact that the element radiographically denser than calcium aluminate comprises iterium, hafnium, gadolinium, tungsten, thorium, uranium, yttrium, dysprosium, erbium, cerium and compositions of themselves.
Petition 870180071402, of 08/15/2018, p. 58/59
1. MOLD COMPOSITION, to melt an article containing titanium, which comprises:
a calcium aluminate cement comprising calcium monoaluminate, calcium dialuminate and mayanite;
a neutron or X-ray detectable element, and characterized by the fact that after a fire discharge, the mold comprises aluminosilicates and calcium aluminosilicates, in which the volume fractions of aluminosilicate and calcium aluminosilicate are less than 5 % by weight.
2. MOLD COMPOSITION, according to the claim
[2]
2 U <
Μ
LU ω

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法律状态:
2018-05-22| B07A| Application suspended after technical examination (opinion) [chapter 7.1 patent gazette]|

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2018-10-09| B09A| Decision: intention to grant [chapter 9.1 patent gazette]|

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2018-12-04| B16A| Patent or certificate of addition of invention granted [chapter 16.1 patent gazette]|Free format text: PRAZO DE VALIDADE: 20 (VINTE) ANOS CONTADOS A PARTIR DE 05/09/2012, OBSERVADAS AS CONDICOES LEGAIS. |

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2021-08-10| B21F| Lapse acc. art. 78, item iv - on non-payment of the annual fees in time|Free format text: REFERENTE A 9A ANUIDADE. |

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2021-11-30| B24J| Lapse because of non-payment of annual fees (definitively: art 78 iv lpi, resolution 113/2013 art. 12)|Free format text: EM VIRTUDE DA EXTINCAO PUBLICADA NA RPI 2640 DE 10-08-2021 E CONSIDERANDO AUSENCIA DE MANIFESTACAO DENTRO DOS PRAZOS LEGAIS, INFORMO QUE CABE SER MANTIDA A EXTINCAO DA PATENTE E SEUS CERTIFICADOS, CONFORME O DISPOSTO NO ARTIGO 12, DA RESOLUCAO 113/2013. |

优先权:

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申请号 | 申请日 | 专利标题

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US13/250,726|US8579013B2|2011-09-30|2011-09-30|Casting mold composition with improved detectability for inclusions and method of casting|

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US13/250,726|2011-09-30|

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PCT/US2012/053716|WO2013081701A2|2011-09-30|2012-09-05|Casting mold composition with improved detectability for inclusions and method of casting|

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