Patent Grant
9034247
A high-temperature, high-strength Co—Ni base alloy and a method of making an article therefrom are disclosed. More particularly, a gamma prime (γ′) strengthened Co—Ni base alloy that is capable of forming an alumina surface layer or scale is disclosed together with a process for producing the same. These alloys are suitable for making articles for applications where high temperature strength and oxidation resistance are required.
In a number of high-temperature, high-strength applications, particularly for use in industrial gas turbines, as well as engine members for aircraft, chemical plant materials, engine members for automobile such as turbocharger rotors, high temperature furnace materials and the like, high strength is needed under a high temperature operating environment, as well as excellent oxidation resistance. In some of these applications, Ni-base superalloys and Co-base alloys have been used. These include Ni-base superalloys which are strengthened by the formation of a γ′ phase having an ordered face-centered cubic L12 structure: Ni3(Al,Ti), for example. It is preferable that the γ′ phase is used to strengthen these materials because it has an inverse temperature dependence in which the strength increases together with the operating temperature.
In high-temperature, high-strength applications where corrosion resistance and ductility are required, Co-base alloys are commonly used alloys rather than the Ni-base alloys. The Co-base alloys are strengthened with M23C6 or MC type carbides, including Co3Ti, Co3Ta, etc. These have been reported to have the same L12-type structure as the crystal structure of the γ′ phase of the Ni-base alloys. However, Co3Ti and Co3Ta have a low stability at high temperature. Thus, even with optimization of the alloy constituents these alloys have an upper limit of the operating temperature of only about 750° C., which is generally lower than the γ′ strengthened Ni-base alloys.
A Co-base alloy that has an intermetallic compound of the L12 type [Co3(Al,W)] dispersed and precipitated therein, where part of the Co may be replaced with Ni, Ir, Fe, Cr, Re, or Ru, while part of the Al and W may be replaced with Ni, Ti, Nb, Zr, V, Ta or Hf, has been disclosed in US2008/0185078. Under typical oxidation conditions, the Co-base alloys strengthened with Co3(Al,W) typically form cobalt-rich oxides, such as CoO, Co3O4 and CoWO4, which are not protective and result in poor oxidation and corrosion resistance. While good high-temperature strength and microstructure stability have been reported for this alloy, further improvement of the high-temperature properties are desirable, particularly improved high-temperature oxidation and corrosion resistance.
According to one aspect of the invention, a cobalt-nickel base alloy is disclosed. The cobalt-nickel base alloy, comprises, in weight percent: greater than about 4% of Al, about 10 to about 20% of W, about 10 to about 40% Ni, about 5 to 20% Cr and the balance Co and incidental impurities. The alloy has a microstructure that is substantially free of a CoAl phase having an ordered body-centered cubic B2 crystal structure and configured to form a continuous, adherent aluminum oxide layer on an alloy surface upon exposure to a high-temperature oxidizing environment.
According to another aspect of the invention, a method of making an article having high-temperature strength, oxidation resistance and corrosion resistance is disclosed. The method comprises: forming a cobalt-nickel base alloy, comprising, in weight percent: greater than about 4% of Al, about 10 to about 20% of W, about 10 to about 40% Ni, about 5 to 20% Cr and the balance Co and incidental impurities; forming an article from the cobalt-nickel base alloy; solution-treating the cobalt-nickel base alloy by a solution heat treatment at a solutionizing temperature that is above the gamma prime solvus temperature and below the solidus temperature for a predetermined solution-treatment time; and aging the cobalt-nickel base alloy by providing at least one aging heat treatment at an aging temperature that is less than the gamma-prime solvus temperature for a predetermined aging time to form an alloy microstructure that comprises a plurality of gamma prime precipitates comprising (Co,Ni)3(Al,W) and is substantially free of a CoAl phase having a B2 crystal structure, wherein the alloy is configured to form a continuous, adherent aluminum oxide layer on an alloy surface upon exposure to a high-temperature oxidizing environment.
These and other advantages and features will become more apparent from the following description taken in conjunction with the drawings.
The subject matter, which is regarded as 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 invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which:
The detailed description explains embodiments of the invention, together with advantages and features, by way of example with reference to the drawings.
Referring to
The Co—Ni-base alloys 2 disclosed herein generally comprise, in weight percent, greater than about 4% of Al, about 10 to about 20% of W, about 10 to about 40% Ni, about 5 to 20% Cr and the balance Co and incidental impurities. The alloy composition range was selected to provide preferential outward diffusion of Al to form a surface alumina layer. The amount of alloying elements will generally be selected to provide sufficient Ni to form a predetermined volume quantity of [(Co,Ni)3(Al,W)] precipitates, which contribute to the desirable high-temperature alloy characteristics described above. More particularly, the alloy may include about 15% to about 35% by weight of Ni, and even more particularly may include about 20% to about 35% by weight of Ni. The Al amount will generally be selected to provide a tightly adherent surface aluminum oxide layer 4 that includes aluminum oxide, and more particularly that includes alumina 5 (Al2O3). This may include greater than about 4% by weight of Al, and more particularly may include greater than about 4% to about 6% by weight of Al. The Cr amount will generally be selected to promote formation of a continuous, adherent alumina layer on the surface of the substrate alloy. This may include about 5% to about 20% by weight of Cr, and more particularly may include greater than about 7% to about 15% by weight of Cr. These Co—Ni-base alloys 2 also may include other alloying additions as described further herein. The Co—Ni-base alloys disclosed herein generally comprise an alloy microstructure that includes a solid-solution gamma (γ) phase matrix 6, where the solid-solution comprises (Co, Ni) with various other substitutional alloying additions as described herein. The alloy microstructure also includes a gamma prime (γ′) phase 8 that includes a plurality of dispersed precipitate particles 9 that precipitate in the gamma matrix 6 during processing of the alloy as described herein. The γ′ precipitates act as a strengthening phase and provide the Co—Ni-base alloys with their desirable high-temperature characteristics. Alloying additions other than those described above may be used to modify the gamma phase, such as to promote the formation and growth of the aluminum oxide layer 4 on the surface, or to promote the formation and affect the characteristics of the γ′ precipitates as described herein.
The γ′ phase 8 precipitates 9 comprise an intermetallic compound comprising [(Co,Ni)3(Al,W)] and have an L12 crystal structure. The lattice mismatch between the γ matrix 6 and the γ′ phase 8 precipitates 9 dispersed therein that is used as a strengthening phase in the disclosed Co—Ni-base alloys 2 may be up to about 0.5%. This is significantly less than the mismatch of the lattice constant between the γ matrix 6 and the γ′ phase precipitates comprising Co3Ti and/or Co3Ta in Co-base alloys, where the lattice mismatch may be 1% or more, and which have a lower creep resistance than the alloys disclosed herein. Further, by controlling the aluminum content of the Co—Ni-base alloys disclosed herein, as well as the contents of other alloy constituents such as Ti and Cr, the alloys provide an adherent, continuous aluminum oxide layer 4 on the alloy surface that continues to increase in thickness and provide enhanced protection during their high-temperature use.
The size and volume quantity of the γ′ phase 8 [(Co,Ni)3(Al,W)] precipitates 9 may be controlled to provide a predetermined particle size, such as a predetermined average particle size, and/or a predetermined volume quantity, by appropriate selection and processing of the alloys, including selection of the constituent amounts of the elements comprising the precipitates, as well as appropriate time and temperature control during solution heat treatment and aging heat treatment, as described herein. In one exemplary embodiment, the γ′ phase 8 [(Co,Ni)3(Al,W)] precipitates 9 may be precipitated under conditions where the average precipitate particle diameter is about 1 μm or less, and more particularly about 500 nm or less. In another exemplary embodiment, the precipitates may be precipitated under conditions where their volume fraction is about 5 to 90%, and more particularly about 25 to about 85%. For larger particle diameters, the mechanical properties such as strength and hardness may be reduced. For smaller precipitate amounts, the strengthening is insufficient and for larger amount, the ductility may be reduced.
In the Co—Ni-base alloys 2 of the present invention, the alloy constituents have been described generally as comprising, in weight percent, greater than about 4% of Al, about 10 to about 20% of W, about 10 to about 40% Ni, about 5 to 20% Cr and the balance Co and incidental impurities. The amounts of Ni and Al will generally be selected to provide sufficient amounts of these constituents to form a predetermined volume quantity and/or predetermined particle size of [(Co,Ni)3(Al,W)] precipitates, which contribute to the desirable high-temperature alloy characteristics described above. In addition, other alloy constituents may be selected to promote the high-temperature properties of the alloy, particularly the formation and high-temperature stability over time of the [(Co,Ni)3(Al,W)] precipitates 9, the formation and growth of the adherent, continuous aluminum oxide layer 4 on the surface and ensuring that the alloy 2 is substantially free of the CoAl beta phase.
Ni is a major constituent of the γ and γ′ phases. The amount of Ni is selected to limit the effect on the γ phase, such as, for example, reduction in the melting point from that characteristic of Co (1495° C.) for Co-base alloys to that of Ni (1453° C.) for Ni-base alloys. The amount of Ni is also selected to promote formation of [(Co,Ni)3(Al,W)] precipitates having the desirable L12 crystal structure that provide the reduced lattice mismatch as compared to Co-base alloys. In an exemplary embodiment, the alloy may include greater than about 10% to about 40% of Ni, and more particularly may include about 15% to about 35% by weight of Ni, and even more particularly may include about 20% to about 35% by weight of Ni.
Al is also a major constituent of the γ′ phase 8 and also contributes to the improvement in oxidation resistance by formation of an adherent, continuous aluminum oxide layer 4 on the surface, which in an exemplary embodiment comprises alumina 5 (Al2O3). The amount of aluminum included in the alloy must be sufficiently large to form the adherent, continuous aluminum oxide layer 4 on the surface, and may also be selected to provide sufficient aluminum to enable continued growth of the thickness of the aluminum oxide layer 4 on the surface during high-temperature operation of articles formed from the alloy. The amount of aluminum included in these alloys must be also be sufficiently small to ensure that the alloys are substantially free of the CoAl beta phase with a B2 crystal structure, since the presence of this phase tends to significantly reduce their high temperature strength. In an exemplary embodiment, the alloy 2 may include greater than about 4% by weight of Al, and more particularly may include greater than about 4% to about 6% by weight of Al. Lower amounts of Al will prevent the formation of the adherent, continuous aluminum oxide layer 4 on the alloy surface and higher amounts of aluminum will promote the formation of a CoAl beta phase with a B2 crystal structure.
W is also a major constituent element of the γ′ phase 8 and also has an effect of solid solution strengthening of the matrix, particularly due to its larger atomic size as compared to that of Co, Ni and Al. In an exemplary embodiment, the alloy 2 may include about 10% to about 20% by weight of W. Lower amounts of W will result in formation of an insufficient volume fraction of γ′ phase and higher amounts of W will result in the formation of undesirable phases, such as μ-Co7W6 and Co3W phases.
In addition, the Co—Ni-base alloys 2 disclosed herein may also include a predetermined amount of Si or S, or a combination thereof. In another exemplary embodiment, Si may be added in an amount effective to enhance the oxidation resistance of the Co—Ni base alloys, and may include about 0.01% to about 1% by weight of the alloy. In yet another exemplary embodiment, S may be controlled as an incidental impurity to also enhance the oxidation resistance of the Co—Ni base alloys, and may be reduced to an amount of less than about 5 ppm by weight of the alloys, and more particularly may be reduced to an amount of less than about 1 ppm by weight of the alloys. The reduction of S as an incidental impurity to the levels described is generally effective to improve the oxidation resistance of the alloys 2 and improve alumina scale adhesion, resulting in adherent aluminum oxide scales that are resistant to spallation.
Further, the Co—Ni-base alloys 2 disclosed herein may also include a predetermined amount of Ti effective to promote the formation of the adherent, continuous aluminum oxide layer 4 on the alloy surface. In one exemplary embodiment, Ti may include up to about 10% of the alloy, and more particularly up to about 5% of the alloy.
These Co—Ni-base alloys 2 are advantageously substantially free of macro segregation of the alloy constituents, particularly Al, Ti or W, or a combination thereof, such as is known to occur in Ni-base superalloys upon solidification. More particularly, these alloys are substantially free of macro segregation of the alloy constituents, including those mentioned, in the interdendritic spaces of castings. This is a particularly desirable aspect at the surface of these alloys because macro segregation can cause pits or pimples (protrusions) to form at the alloy surface of Ni-base superalloys during high temperature oxidation. Such pits or pimples are mixed oxides or spinel, such as mixed oxides of magnesium, ferrous iron, zinc, or manganese, in any combination.
Other alloy constituents may be selected to modify the properties of the Co—Ni-base alloys 2. In an exemplary embodiment, constituents may be selected from the group consisting of B, C, Y, Sc, lanthanides, misch metal, and combinations thereof. In one exemplary embodiment the total content of constituents from this group may be selected from the range of about 0.001 to about 2.0% by weight of the alloy.
B is generally segregated in the γ phase 6 grain boundaries and contributes to the improvement in the high temperature strength of the alloys. The addition of B in amounts of about 0.001% to about 0.5% by weight is generally effective to increase the strength and ductility of the alloy, and more particularly about 0.001% to about 0.1% by weight.
C is also generally segregated in the γ phase 6 grain boundaries and contributes to the improvement in the high temperature strength of the alloys. It is generally precipitated as a metal carbide to enhance the high-temperature strength. The addition of C in amounts of about 0.001% to about 1% by weight is generally effective to increase the strength of the alloy, and more particularly about 0.001% to about 0.5% by weight.
Y, Sc, the lanthanide elements, and misch metal are generally effective in improving the high-temperature oxidation resistance of the alloys. The addition of these elements, in total, in amounts of about 0.01% to about 0.5% by weight is generally effective to improve the oxidation resistance of the alloy and improve alumina scale adhesion, and more particularly about 0.001% to about 0.2% by weight. These elements may also be included together with control of the sulfur content to improve the oxidation resistance of these alloys 2 and improve alumina scale adhesion. When reactive elements or rare earths are employed in these alloys 2, it is desirable that the materials of the ceramic systems used as casting molds which contact the alloy be selected to avoid depletion of these elements at the alloy 2 surface. Thus, the use of Si-based ceramics in contact with the alloy 2 surface is generally undesirable, as they cause depletion of rare earth elements in the alloy which can react with the Si-based ceramics to form lower melting point phases. In turn, this can result in defects leading to lower low cycle fatigue (LCF) strength and reduced creep strength. The use of ceramic systems that employ non-reactive face coats on the ceramic (e.g., Y2O3 flour) or Al-based ceramics is desirable when reactive elements or rare earth elements are employed as alloy 2 constituents.
Mo may be employed as an alloy constituent to promote stabilization of the γ′ phase and provide solid solution strengthening of the γ matrix. The addition of Mo in amounts of up to about 10% by weight is generally effective to provide these benefits, and more particularly up to about 5% by weight.
Re and Ru may be employed as alloy constituents to improve the oxidation resistance of Co—Ni-base alloys. The addition of Re or Ru, or a combination of them, in a total amount of up to about 10% by weight is generally effective to provide this benefit, and more particularly a total amount of up to about 5% by weight.
Ti, Nb, Zr, V, Ta, and Hf may also be employed as alloy constituents to provide stabilization of the γ′ phase 8 and improvement of the high temperature strength of Co—Ni-base alloys 2. As indicated, the amount of these elements in total may include about 0% to about 15% of the alloy. When employed, the addition of these elements in the following amounts is generally effective to provide these benefits, including: Ti of up to about 10%, and more particularly, up to about 5%; Nb of up to about 10%, and more particularly, up to about 5%; Zr of up to about 3.0%, and more particularly, about up to 1%; V of up to about 5%, and more particularly, up to about 2%; Ta of up to about 15%, and more particularly, up to about 12%; and Hf of up to about 3%, and more particularly, up to about 2%. Amounts in excess of these limits may reduce the high-temperature strength and reduce the solidus temperature of the alloy, thereby reducing its operating temperature range, and more particularly its maximum operating temperature.
As illustrated in
Referring to
Melting 110 of the Co—Ni-base alloy 2 may be performed by any suitable melting method, including vacuum induction melting (VIM), vacuum arc remelting (VAR) or electro-slag remelting (ESR). In the case where the molten Co—Ni-base alloy, which is adjusted to a predetermined composition, is used as a casting material, it may be produced by any suitable casting method, including various investment casting, directional solidification or single crystal solidification methods.
Forming 120 of an article 10 having a predetermined shape from the cobalt-nickel base alloy 2 may be done by any suitable forming method. In an exemplary embodiment, the cast alloy can be hot-worked, such as by forging at a solution treatment temperature and may also be cold-worked. Therefore, the Co—Ni-base alloy 2 can be formed into many intermediate shapes, including various forging billets, plates, bars, wire rods and the like. It can also be processed into many finished or near net shape articles 10 having many different predetermined shapes, including those described herein. Forming 120 may be done prior to solution-treating 130 as illustrated in
Solution-treating 130 of the cobalt-nickel base alloy 2 may be performed by a solution heat treatment at a solutionizing temperature that is between the γ′ solvus temperature and the solidus temperature for a predetermined solution-treatment time. The Co—Ni-base alloy 2 is formed into an article 10 having a predetermined shape and then heated at the solutionizing temperature. In an exemplary embodiment, the solutionizing temperature may be between about 1100 to about 1400° C., and more particularly may be between about 1150 to about 1300° C., for a duration of about 0.5 to about 12 hours. The strain introduced by forming 120 is removed and the precipitates are solutionized by being dissolved into the matrix 6 in order to homogenize the material. At temperatures below the solvus temperature, neither the removal of strain nor the solutionizing of precipitates is accomplished. When the solutionizing temperature exceeds the solidus temperature, some liquid phase is formed and coarsening growth of the crystal grains occurs, which reduces the high-temperature strength of the article 10.
Aging 140 of the cobalt-nickel base alloy 2 is performed by providing at least one aging heat treatment at an aging temperature that is lower than the γ′ solvus temperature for a predetermined aging time, where the time is sufficient to form an alloy microstructure that comprises a plurality of γ′ precipitates comprising [(Co,Ni)3(Al,W)] and is substantially free of a CoAl phase having a B2 crystal structure. In an exemplary embodiment, the aging treatment may be performed at a temperature of about 700 to about 1200° C., to precipitate [(Co,Ni)3(Al,W)] having an L12-type crystal structure that has a lower lattice constant mismatch between the γ′ precipitate and the γ matrix. The cooling rate from the solution-treating 130 to aging 140 may also be used to control aspects of the precipitation of the γ′ phase, including the precipitate size and distribution within the γ matrix. The aging heat treatment may be conducted in one, or optionally, in more than one heat treatment step, including two steps and three steps. The heat treatment temperature may be varied as a function of time within a given step. In the case of more than one step, the steps may be performed at different temperatures and for different durations, such as for example, a first step at a higher temperature and a second step at a somewhat lower temperature.
Either or both of solution treating 130 and aging 140 heat treatments may be performed in a heat treating environment that is selected to reduce the formation of the surface layer of alumina, including vacuum, inert gas and reducing atmosphere heat treating environments. This may be employed, for example, to limit the formation of the aluminum oxide layer 4 on the surface of the alloy prior to coating the surface of the alloy with a thermal barrier coating material to improve the bonding of the coating material to the alloy surface.
Referring to
In a Ni—Al binary system, γ′ is a thermodynamically stable Ni3Al phase with an L12 crystal structure in an equilibrium phase diagram and is used as a strengthening phase. Thus, in Ni-base alloys using this system as a basic system, γ′ has been used as a primary strengthening phase. In contrast, in an equilibrium phase diagram of the Co—Al binary system, a γ′ Co3Al phase is not present and has been reported that the γ′ phase is a metastable phase. The metastable γ′ phase has reportedly been stabilized by the addition of W in order to use the γ′ phase as a strengthening phase of various Co-base alloys. Without being bound by theory, in the Co—Ni solid solution alloys disclosed herein, the γ′ phase described as a [(Co,Ni)3(Al,W)] phase with an L12 crystal structure may comprise a mixture of a thermodynamically stable Ni3Al with an L12 crystal structure and metastable Co3(Al,W) that is stabilized by the presence of W that also has an L12 crystal structure. In any case, the γ′ phase comprising a [(Co,Ni)3(Al,W)] phase with an L12 crystal structure is precipitated as a thermodynamically stable phase.
In an exemplary embodiment, the γ′ phase intermetallic compound [(Co,Ni)3(Al,W)] is precipitated according to method 100, and more particularly aging 140, in the γ phase matrix 6 under conditions sufficient to provide a particle diameter of about 1 m or less, and more particularly, about 10 nm to about 1 μm, and even more particularly about 50 nm to about 1 μm, and the amount of γ′ phase precipitated is about 5% or more by volume, and more particularly about 25 to about 85% by volume.
An exemplary embodiment of an alloy having a composition, by weight, of Co-30% Ni-4.4% Al-13.2% W-9.5% Cr-6.9% Ta-0.05% C-0.005% B-0.05% La was prepared by induction melting. The alloy was solution heat treated at 1250° C. for 2 hours and then aged at 950° C. for 100 hours. Cylindrical specimens 0.9″ long and 0.17″ in diameter were machined from the alloy and several comparative alloys and exposed to a high-temperature oxidizing environment to test and demonstrate the oxidation characteristics of the alloy. As used herein, a high-temperature oxidizing environment, such as exists in the hot gas flow path of an industrial gas turbine engine during its operation, may be defined as an environment wherein alloy 2 articles 10 that are located therein may experience temperatures of 1650° F. or more in the presence of oxygen sufficient to cause their oxidation, and more particularly, may include environments that may experience temperatures of 1800° F. or more in the presence of oxygen sufficient to cause their oxidation. Cyclic oxidation tests were conducted in air with a cycle consisting of holding the samples at 1800° F. in air for 50 min and then cooling the samples in air to room temperature for 10 min Tests were completed at 1000 thermal cycles. Samples were weighed at various intervals during the test to monitor the weight change due to oxide formation or spallation. Oxides formed on the surface were analyzed by X-ray diffraction (XRD) and electron probe micro analysis (EPMA).
The alloy of this example was also compared to several other related art alloys as described in US2008/0185078 (alloys 31 and 32, Table 6) and US2010/0061883 (alloys Co-01 and Co-02, Table 2), which were also prepared by induction melting. The alloy compositions are shown in
The terms “first,” “second,” and the like, “primary,” “secondary,” and the like, as used herein do not denote any order, quantity, or importance, but rather are used to distinguish one element from another.
The terms “a” and “an” do not denote a limitation of quantity, but rather denote the presence of at least one of the referenced item.
Unless defined otherwise, technical and scientific terms used herein have the same meaning as is commonly understood by one of skill in the art to which this invention belongs.
The modifier “about” used in connection with a quantity is inclusive of the stated value and has the meaning dictated by the context (e.g., includes the degree of error associated with measurement of the particular quantity). The endpoints of all ranges directed to the same component or property are inclusive of the endpoint and independently combinable.
As used herein, “combination” is inclusive of blends, mixtures, alloys, reaction products, and the like.
Reference throughout the specification to “one embodiment”, “another embodiment”, “an embodiment”, and so forth, means that a particular element (e.g., feature, structure, and/or characteristic) described in connection with the embodiment is included in at least one embodiment described herein, and may or may not be present in other embodiments. In addition, it is to be understood that the described elements may be combined in any suitable manner in the various embodiments.
In general, the compositions or methods may alternatively comprise, consist of, or consist essentially of, any appropriate components or steps herein disclosed. The invention may additionally, or alternatively, be formulated so as to be devoid, or substantially free, of any components, materials, ingredients, adjuvants, or species, or steps used in the prior art compositions or that are otherwise not necessary to the achievement of the function and/or objectives of the present claims.
As used herein, unless the text specifically indicates otherwise, reference to a weight or volume percent of a particular alloy constituent or combination of constituents, or phase or combination of phases, refers to its percentage by weight or volume of the overall alloy, including all of the alloy constituents.
While 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. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the invention. Additionally, while various embodiments of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.
| Number | Name | Date | Kind |
|---|---|---|---|
| 4078922 | Magyer | Mar 1978 | A |
| 4152181 | Hirrakis | May 1979 | A |
| 5439640 | Heck et al. | Aug 1995 | A |
| 20050227106 | Schlichting et al. | Oct 2005 | A1 |
| 20070054147 | Imano et al. | Mar 2007 | A1 |
| 20080185075 | Ishida et al. | Aug 2008 | A1 |
| 20080185078 | Ishida et al. | Aug 2008 | A1 |
| 20080206090 | Ishida et al. | Aug 2008 | A1 |
| 20100061883 | Nazmy et al. | Mar 2010 | A1 |
| 20100291406 | Suzuki et al. | Nov 2010 | A1 |
| 20110268989 | Suzuki et al. | Nov 2011 | A1 |
| Number | Date | Country |
|---|---|---|
| 1410872 | Apr 2004 | EP |
| 1584871 | Oct 2005 | EP |
| 2251446 | Nov 2010 | EP |
| 2383356 | Nov 2011 | EP |
| 62228444 | Oct 1987 | JP |
| 2141523 | May 1990 | JP |
| 2009228024 | Oct 2009 | JP |
| Entry |
|---|
| Osaki et al., English machine translation of JP 2009-228024, Oct. 2009, p. 1-16. |
| C. Cui, D. Ping, Y. Gu, H. Harada, A New Co-Base Superalloy Strengthened by y' Phase, Materials Transactions, (2006) pp. 2099 to 2102, vol. 47, No. 8, High Temperature Materials Center, National Institute for Materials Science, Tsukuba 305-0047, Japan. |
| J. Sato, T. Omari, K. Oikawa, I. Ohnuma, R. Kainuma, K. Ishida, “Cobalt-Base High-Temperature Alloys”, Science, vol. 312, (2006) pp. 90-91. |
| EP Search Report EP Application Serial No. 12171280.6 dated Sep. 26, 2012. |
| Number | Date | Country | |
|---|---|---|---|
| 20120312426 A1 | Dec 2012 | US |
