WO2019099719A1

WO2019099719A1 - Cobalt-chromium-aluminum alloys, and methods for producing the same

Info

Publication number: WO2019099719A1
Application number: PCT/US2018/061356
Authority: WO
Inventors: Jen C. Lin; Daniel J. SAUZA
Original assignee: Arconic Inc.
Priority date: 2017-11-16
Filing date: 2018-11-15
Publication date: 2019-05-23

Abstract

New cobalt-based alloys are disclosed. The new cobalt-based alloys generally include from 26 to 30 wt. % Cr, from 4 to 6 wt. % Al, up to 20 wt. % Ni, up to 5 wt. % Fe, up to 3 wt. % Nb, up to 3 wt. % Mo, up to 2 wt. % Ti, up to 5 wt. % W, up to 0.5 wt. % C, and up to 0.5 wt. % B. The balance of the new cobalt-based alloys may be cobalt, optional incidental elements and unavoidable impurities. The new cobalt-based alloys may realize an improved combination of properties, such as an improved combination of two or more of density, strength, ductility, oxidation resistance, and a narrow non-equilibrium freezing range, among others.

Description

COBALT-CHROMIUM-ALUMINUM ALLOYS, AND METHODS FOR

PRODUCING THE SAME

BACKGROUND

[001] Cobalt-based alloys are useful in a variety of applications. Cobalt-based alloy products are generally produced via casting or wrought processes. Casting generally involves casting a molten cobalt-based alloy into its final form, such as via high pressure die, permanent mold, green and dry-sand, investment, or plaster casting. Wrought products are generally produced by casting a molten cobalt-based alloy into ingot or billet. The ingot or billet is generally further hot worked, sometimes with cold work, to produce its final form.

FIELD OF THE INVENTION

[002] The field of the invention relates to cobalt-chromium-aluminum alloys, and methods for producing the same.

SUMMARY OF THE DISCLOSURE

[003] Broadly, the present patent application relates to new cobalt-based alloys, and methods for producing the same. The new cobalt-based alloys may realize an improved combination of properties, such as an improved combination of two or more of density, strength, ductility, oxidation resistance, and a narrow non-equilibrium freezing range, among others.

[004] As used herein, “cobalt-based alloy” means an alloy having cobalt (Co) as its predominant alloying element. Generally, the new cobalt-based alloys generally comprise (and some instances consist essentially of, or consist of) cobalt (Co), chromium (Cr), and aluminum (Al), optionally with one or more of nickel (Ni), iron (Fe), niobium (Nb), molybdenum (Mo), titanium (Ti), tungsten (W), carbon (C) and boron (B). The new cobalt-based alloys generally include from 26 to 30 wt. % Cr, from 4 to 6 wt. % Al, up to 20 wt. % Ni, up to 5 wt. % Fe, up to 3 wt. % Nb, up to 3 wt. % Mo, up to 2 wt. % Ti, up to 5 wt. % W, up to 0.5 wt. % C, and up to 0.5 wt. % B. The balance of the new cobalt-based alloys may be cobalt, optional incidental elements, and unavoidable impurities.

[005] In one embodiment, a cobalt-based alloy comprises from 26 to 30 wt. % Cr, from 4 to 6 wt. % Al, up to 20 wt. % Ni, up to 5 wt. % Fe, up to 3 wt. % Nb, up to 3 wt. % Mo, up to 5 wt. % W, up to 2 wt. % Ti, up to 0.5 wt. % C, and up to 0.5 wt. % B.

[006] In some of the above embodiments, a cobalt-based alloy includes at least 45 wt. % Co. In some of the above embodiments, a cobalt-based alloy includes or at least 50 wt. % Co. In some of the above embodiments, a cobalt-based alloy includes least 55 wt. % Co. In some of the above embodiments, a cobalt-based alloy includes least 60 wt. % Co.

[007] In some of the above embodiments, a cobalt-based alloy includes not greater than 70 wt. % Co. In some of the above embodiments, a cobalt-based alloy includes not greater than 68 wt. % Co.

[008] In some of the above embodiments, a cobalt-based alloy includes at least 27 wt. % Cr. In some of the above embodiments, a cobalt-based alloy includes not greater than 29 wt. % Cr.

[009] In some of the above embodiments, a cobalt-based alloy includes at least 4.5 wt. % Al. In some of the above embodiments, a cobalt-based alloy includes not greater than 5.5 wt. % Al.

[0010] In some of the above embodiments, a cobalt-based alloy includes at least 0.5 wt. % Ni. In some of the above embodiments, a cobalt-based alloy includes at least 1.0 wt. % Ni. In some of the above embodiments, a cobalt-based alloy includes not greater than 15 wt. % Ni. In some of the above embodiments a cobalt-based alloy includes not greater than 10 wt. % Ni. In some of the above embodiments, a cobalt-based alloy includes greater than 5 wt. % Ni. In some of the above embodiments, a cobalt-based alloy includes low amounts of nickel, having less than 0.5 wt. % Ni.

[0011] In some of the above embodiments, a cobalt-based alloy includes at least 0.5 wt. % Fe. In some of the above embodiments, a cobalt-based alloy includes at least 1.0 wt. % Fe. In some of the above embodiments a cobalt-based alloy includes at least 1.0 wt. % Fe. In some of the above embodiments, a cobalt-based alloy includes at least 1.5 wt. % Fe. In some of the above embodiments, a cobalt-based alloy includes at least 2.0 wt. % Fe. In some of the above embodiments, a cobalt-based alloy includes at least 2.5 wt. % Fe. In some of the above embodiments, a cobalt-based alloy includes at least 3.0 wt. % Fe. In some of the above embodiments, a cobalt-based alloy includes low amounts of iron, having less than 0.5 wt. %

Fe.

[0012] In some of the above embodiments, a cobalt-based alloy includes at least 0.5 wt. % Nb. In some of the above embodiments, a cobalt-based alloy includes at least 1.0 wt. % Nb. In some of the above embodiments, a cobalt-based alloy includes at least 2.0 wt. % Nb. In some of the above embodiments, a cobalt-based alloy includes low amounts of niobium, having less than 0.5 wt. % Nb. [0013] In some of the above embodiments, a cobalt-based alloy includes at least 0.5 wt. % Mo. In some of the above embodiments, a cobalt-based alloy includes at least 1.0 wt. % Mo. In some of the above embodiments, a cobalt-based alloy includes at least 1.5 wt. % Mo. In some of the above embodiments, a cobalt-based alloy includes at least 2.0 wt. % Mo. In some of the above embodiments, a cobalt-based alloy includes not greater than 2.5 wt. % Mo. In some of the above embodiments, a cobalt-based alloy includes low amounts of molybdenum, having less than 0.5 wt. % Mo.

[0014] In some of the above embodiments, a cobalt-based alloy includes at least 0.5 wt. % W. In some of the above embodiments, a cobalt-based alloy includes at least 1.0 wt. % W. In some of the above embodiments, a cobalt-based alloy includes not greater than 4 wt. % W. In some of the above embodiments, a cobalt-based alloy includes not greater than 3 wt. % W. In some of the above embodiments, a cobalt-based alloy includes not greater than 2 wt. % W. In some of the above embodiments, a cobalt-based alloy includes low amounts of tungsten, having less than 0.5 wt. % W.

[0015] In some of the above embodiments, the total amount of niobium plus molybdenum plus tungsten in the cobalt-based alloy does not exceed 6 wt. %. In some of the above embodiments, the total amount of niobium plus molybdenum plus tungsten in the cobalt-based alloy does not exceed 5 wt. %. In some of the above embodiments, the total amount of niobium plus molybdenum plus tungsten in the cobalt-based alloy does not exceed 4 wt. %.

[0016] In some of the above embodiments, a cobalt-based alloy includes at least 0.2 wt. % Ti. In some of the above embodiments, a cobalt-based alloy includes at least 0.5 wt. % Ti. In some of the above embodiments, a cobalt-based alloy includes at least 1.0 wt. % Ti. In some of the above embodiments, a cobalt-based alloy includes at least 1.5 wt. % Ti. In some of the above embodiments, a cobalt-based alloy includes low amounts of titanium, having less than 0.2 wt. % Ti.

[0017] In some of the above embodiments, a cobalt-based alloy includes at least 0.01 wt. % C. In some of the above embodiments, a cobalt-based alloy includes at least 0.05 wt. % C. In some of the above embodiments, a cobalt-based alloy includes at least 0.10 wt. % C.

[0018] In some of the above embodiments, a cobalt-based alloy includes not greater than 0.20 wt. % C. In some of the above embodiments, a cobalt-based alloy includes low amounts of carbon, having less than 0.01 wt. % C. [0019] In some of the above embodiments, a cobalt-based alloy includes at least 0.01 wt. %. In some of the above embodiments, a cobalt-based alloy includes at least 0.05 wt. % B. In some of the above embodiments, a cobalt-based alloy includes not greater than 0.20 wt. % B. In some of the above embodiments, a cobalt-based alloy includes low amounts of boron, having less than 0.01 wt. % B.

[0020] In some of the above embodiments, the balance of the cobalt-based alloy is cobalt, any optional incidental elements, and unavoidable impurities.

[0021] In some of the above embodiments, a cobalt-based alloy comprises a fine eutectic-type structure. In some of the above embodiments, the fine eutectic-type structure comprises at least cellular structures. In some of the above embodiments, the fine eutectic- structure realizes an average eutectic spacing of not greater than 10 micrometers. In some of the above embodiments, the fine eutectic-structure realizes an average eutectic spacing of not greater than 8 micrometers. In some of the above embodiments, the fine eutectic-structure realizes an average eutectic spacing of not greater than 5 micrometers. In some of the above embodiments, the fine eutectic-structure realizes an average eutectic spacing of not greater than 4 micrometers. In some of the above embodiments, the fine eutectic-structure realizes an average eutectic spacing of not greater than 3 micrometers. In some of the above embodiments, the fine eutectic-structure realizes an average eutectic spacing of not greater than 2 micrometers. In some of the above embodiments, the fine eutectic-structure realizes an average eutectic spacing of not greater than 1 micrometers. In some of the above embodiments, the fine eutectic- structure realizes an average eutectic spacing of not greater than 0.5 micrometers.

[0022] In some of the above embodiments, a cobalt-based alloy realizes a non-equilibrium freezing range of not greater than l50°C. In some of the above embodiments, a cobalt-based alloy realizes a non-equilibrium freezing range of not greater not greater than l00°C. In some of the above embodiments, a cobalt-based alloy realizes a non-equilibrium freezing range of not greater not greater than 75°C.

[0023] In some of the above embodiments, a cobalt-based alloy realizes a density of not greater than 8.4 g/cc. In some of the above embodiments, a cobalt-based alloy realizes a density of not greater than greater than not greater than 8.3 g/cc. In some of the above embodiments, a cobalt-based alloy realizes a density of not greater than greater than 8.2 g/cc. In some of the above embodiments, a cobalt-based alloy realizes a density of not greater than greater than 8.1 g/cc. [0024] In some of the above embodiments, a cobalt-based alloy includes an AI2O3 layer at least partially covering its surface. In some of the above embodiments, a cobalt-based alloy includes an AI2O3 layer covering the entirety of its surface.

[0025] In some of the above embodiments, a cobalt-based alloy realizes a determined metal loss of not greater than 500 microns. In some of the above embodiments, a cobalt-based alloy realizes a determined metal loss of not greater than 400 microns. In some of the above embodiments, a cobalt-based alloy realizes a determined metal loss of not greater than 350 microns. In some of the above embodiments, a cobalt-based alloy realizes a determined metal loss of not greater than 300 microns. In some of the above embodiments, a cobalt-based alloy realizes a determined metal loss of not greater than 250 microns. In some of the above embodiments, a cobalt-based alloy realizes a determined metal loss of not greater than 200 microns. In some of the above embodiments, a cobalt-based alloy realizes a determined metal loss of not greater than 150 microns. In some of the above embodiments, a cobalt-based alloy realizes a determined metal loss of not greater than 100 microns.

[0026] In some of the above embodiments, a cobalt-based alloy realizes an fee plus B2 micro structure at a temperature of at least 700°C. In some of the above embodiments, a cobalt- based alloy realizes an fee plus B2 microstructure at a temperature of at least 750°C. In some of the above embodiments, a cobalt-based alloy realizes an fee plus B2 microstructure at a temperature of at least 800°C. In some of the above embodiments, a cobalt-based alloy realizes an fee plus B2 microstructure at a temperature of not greater than 1 l75°C.

[0027] In some of the above embodiments, a cobalt-based alloy includes precipitates, and at least some of the precipitates have a solvus temperature of at least H75°C. In some of the above embodiments, a cobalt-based alloy includes precipitates, and at least some of the precipitates have a solvus temperature at least l225°C. In some of the above embodiments, a cobalt-based alloy includes precipitates, and at least some of the precipitates have a solvus temperature at least l275°C.

[0028] In some of the above embodiments, a cobalt-based alloy includes at least 1 vol. % of B2 phase. In some of the above embodiments, a cobalt-based alloy includes at least 5 vol. % of B2 phase. In some of the above embodiments, a cobalt-based alloy includes at least 10 vol. % of B2 phase. In some of the above embodiments, a cobalt-based alloy includes at least 15 vol. % of B2 phase. In some of the above embodiments, a cobalt-based alloy includes not greater than 35 vol. % of B2 phase. In some of the above embodiments, a cobalt-based alloy includes not greater than 30 vol. % of B2 phase. In some of the above embodiments, a cobalt- based alloy includes not greater than 25 vol. % of B2 phase. In some of the above embodiments, the vol. % of B2 is present at a temperature of at least 700°C. In some of the above embodiments, the vol. % of B2 is present at a temperature of at least 800°C. In some of the above embodiments, the vol. % of B2 is present at a temperature of not greater than 1 l00°C. In some of the above embodiments, the vol. % of B2 is present at a temperature of not greater than l000°C. In some of the above embodiments, the vol. % of B2 is present at a temperature of not greater than 900°C.

[0029] In some of the above embodiments, the cobalt-based alloy is one of a wrought product, a shape-cast product, an ingot, a billet, an additively manufactured product, an additive manufacturing feedstock, or a powder metallurgy product.

[0030] In some of the above embodiments, the cobalt-based alloy is an additively manufactured product. In some of the above embodiments, a cobalt-based alloy additively manufactured product comprises equiaxed grains having an average grain size of from 0.5 to 50 microns. In some of the above embodiments, a cobalt-based alloy additively manufactured product comprises at least 50 vol. % of the equiaxed grains. In some of the above embodiments, a cobalt-based alloy additively manufactured product comprises at least 60 vol. % of the equiaxed grains. In some of the above embodiments, a cobalt-based alloy additively manufactured product comprises at least 70 vol. % of the equiaxed grains. In some of the above embodiments, a cobalt-based alloy additively manufactured product comprises at least 80 vol. % of the equiaxed grains. In some of the above embodiments, a cobalt-based alloy additively manufactured product comprises at least 90 vol. % of the equiaxed grains. In some of the above embodiments, a cobalt-based alloy additively manufactured product comprises at least 95 vol. % of the equiaxed grains. In some of the above embodiments, a cobalt-based alloy additively manufactured product comprises at least 99 vol. % of the equiaxed grains.

[0031] In some of the above embodiments, the equiaxed grains realize an average grain size of not greater than 30 microns. In some of the above embodiments, the equiaxed grains realize an average grain size of not greater than 20 microns. In some of the above embodiments, the equiaxed grains realize an average grain size of not greater than 10 microns. In some of the above embodiments, the equiaxed grains realize an average grain size of not greater than 5 microns. In some of the above embodiments, the equiaxed grains realize an average grain size of not greater than 4 microns. In some of the above embodiments, the equiaxed grains realize an average grain size of not greater than 3 microns. In some of the above embodiments, the equiaxed grains realize an average grain size of not greater than 2 microns.

[0032] In some of the above embodiments, the additively manufactured product is in the as- built condition.

[0033] In some of the above embodiments, a cobalt-based alloy is crack-free.

I. Composition

[0034] As noted above, the new cobalt-based alloys include cobalt as the predominant alloying element. In one embodiment, a new cobalt-based alloy includes at least 45 wt. % Co. In another embodiment, a new cobalt-based alloy includes at least 50 wt. % Co. In yet another embodiment, a new cobalt-based alloy includes at least 55 wt. % Co. In another embodiment, a new cobalt-based alloy includes at least 60 wt. % Co. In one embodiment, a new cobalt- based alloy includes not greater than 70 wt. % Co. In another embodiment, a new cobalt-based alloy includes not greater than 68 wt. % Co.

[0035] As noted above, the new cobalt-based alloys include chromium (Cr) and generally in the range of from 26 to 30 wt. % Cr. In one embodiment, a new cobalt-based alloy includes at least 27 wt. % Cr. In one embodiment, a new cobalt-based alloy includes not greater than 29 wt. % Cr.

[0036] As noted above, the new cobalt-based alloys include aluminum (Al) and generally in the range of from 4 to 6 wt. % Al. In one embodiment, a new cobalt-based alloy includes at least 4.5 wt. % Al. In one embodiment, a new cobalt-based alloy includes not greater than 5.5 wt. % Al.

[0037] As noted above, the new cobalt-based alloys may include nickel (Ni) (e.g., as a partial substitution for cobalt) and in amounts of up to 20 wt. %. When employed, partial substitution of nickel for cobalt may lower cost of the alloy and without material disruption of the microstructure. Nickel may also be used in the new cobalt-based alloys without substitution for cobalt. When nickel is used, a new cobalt-based alloy generally includes at least 0.5 wt. % Ni. In one embodiment, a new cobalt-based alloy includes at least 1.0 wt. % Ni. In one embodiment, a new cobalt-based alloy includes not greater than 15 wt. % Ni. In another embodiment, a new cobalt-based alloy includes not greater than 10 wt. % Ni. In another embodiment, a new cobalt-based alloy includes not greater than 5 wt. % Ni. In some embodiments, a new cobalt-based alloy includes low amounts of nickel, having less than 0.5 wt. % Ni.

[0038] As noted above, the new cobalt-based alloys may include iron (Fe) (e.g., as a partial substitution for cobalt) and in amounts of up to 5.0 wt. %. When employed, partial substitution of iron for cobalt may lower density and/or may lower cost of the alloy, and without material disruption of the microstructure. Iron may also be used in the new cobalt-based alloys without substitution for cobalt. When iron is used, a new cobalt-based alloy generally includes at least 0.5 wt. % Fe. In one embodiment, a new cobalt-based alloy includes at least 1.0 wt. % Fe. In another embodiment, a new cobalt-based alloy includes at least 1.5 wt. % Fe. In yet another embodiment, a new cobalt-based alloy includes at least 2.0 wt. % Fe. In another embodiment, a new cobalt-based alloy includes at least 2.5 wt. % Fe. In yet another embodiment, a new cobalt-based alloy includes at least 3.0 wt. % Fe. In some embodiments, a new cobalt-based alloy includes low amounts of iron, having less than 0.5 wt. % Fe.

[0039] As noted above, the new cobalt-based alloys may include niobium (Nb) and in amounts of up to 3 wt. %. Niobium may facilitate, for instance, corrosion resistance and/or increased strength. When niobium is used, a new cobalt-based alloy generally includes at least 0.5 wt. % Nb. In one embodiment, a new cobalt-based alloy includes at least 1.0 wt. % Nb. In another embodiment, a new cobalt-based alloy includes at least 2.0 wt. % Nb. In some embodiments, a new cobalt-based alloy includes low amounts of niobium, having less than 0.5 wt. % Nb.

[0040] As noted above, the new cobalt-based alloys may include molybdenum (Mo) and in amounts of up to 3 wt. %. Molybdenum may facilitate, for instance, oxidation resistance, corrosion resistance and/or increased strength. When molybdenum is used, a new cobalt-based alloy generally includes at least 0.5 wt. % Mo. In one embodiment, a new cobalt-based alloy includes at least 1.0 wt. % Mo. In another embodiment, a new cobalt-based alloy includes at least 1.5 wt. % Mo. In yet another embodiment, a new cobalt-based alloy includes at least 2.0 wt. % Mo. In one embodiment, a new cobalt-based alloy includes not greater than 2.5 wt. % Mo. In some embodiments, a new cobalt-based alloy includes low amounts of molybdenum, having less than 0.5 wt. % Mo.

[0041] As noted above, the new cobalt-based alloys may include tungsten (W) and in amounts of up to 5 wt. %. Tungsten may facilitate, for instance, wear resistance. When tungsten is used, a new cobalt-based alloy generally includes at least 0.5 wt. % W. In one embodiment, a new cobalt-based alloy includes not greater than 4 wt. % W. In another embodiment, a new cobalt-based alloy includes not greater than 3 wt. % W. In yet another embodiment, a new cobalt-based alloy includes not greater than 2 wt. % W. In one embodiment, a new cobalt- based alloy includes at least 1.0 wt. % W. In some embodiments, a new cobalt-based alloy includes low amounts of tungsten, having less than 0.5 wt. % W.

[0042] In some embodiments, the total amount of niobium plus molybdenum plus tungsten in the new cobalt-based alloys may be limited. In one embodiment, the total amount of niobium plus molybdenum plus tungsten does not exceed 6 wt. % (i.e., Nb+Mo+W < 6 wt. %). In another embodiment, the total amount of niobium plus molybdenum plus tungsten in the new cobalt-based alloys does not exceed 5 wt. % (i.e., Nb+Mo+W < 5 wt. %). In yet another embodiment, the total amount of niobium plus molybdenum plus tungsten in the new cobalt- based alloys does not exceed 4 wt. % (i.e., Nb+Mo+W < 4 wt. %).

[0043] As noted above, the new cobalt-based alloys may include titanium (Ti) and in amounts of up to 2 wt. %. Titanium may facilitate grain refining and/or precipitation of precipitates. When titanium is used, a new cobalt-based alloy generally includes at least 0.2 wt. % Ti. In one embodiment, a new cobalt-based alloy includes at least 0.5 wt. % Ti. In another embodiment, a new cobalt-based alloy includes at least 1.0 wt. % Ti. In yet another embodiment, a new cobalt-based alloy includes at least 1.5 wt. % Ti. In some embodiments, a new cobalt-based alloy includes low amounts of titanium, having less than 0.2 wt. % Ti.

[0044] As noted above, the new cobalt-based alloys may include carbon (C) and/or boron (B), and in amounts of up to 0.5 wt. % each. Carbon and/or boron may facilitate, for instance, formation of carbides and borides, respectively, which may facilitate improved strength. When carbon and/or boron are used, a new cobalt-based alloy generally includes at least 0.01 wt. % C and/or B. In one embodiment, a new cobalt-based alloy includes at least 0.05 wt. % C and/or B. In one embodiment, a new cobalt-based alloy includes at least 0.10 wt. % C and/or B. In one embodiment, a new cobalt-based alloy includes not greater than 0.20 wt. % C and/or B. In one embodiment, a new cobalt-based alloy includes at least 0.10 wt. % C. In one embodiment, a new cobalt-based alloy includes not greater than 0.20 wt. % C. In one embodiment, a new cobalt-based alloy includes 0.05 - 0.20 wt. % C and/or B. In one embodiment, a new cobalt- based alloy includes 0.10 - 0.20 wt. % C. In some embodiments, a new cobalt-based alloy includes low amounts of carbon and boron, having less than 0.01 wt. % C and B. Also, in the cobalt alloy industry, carbon and/or boron may serve multiple purposes. For instance, carbon and boron may facilitate the production of carbides and borides, respectively, which may facilitate strengthening of the new cobalt-based alloys. Carbon and boron may also facilitate strengthening through interstitial strengthening. Furthermore, carbon and/or boron may provide grain boundary modification. Since carbon and boron are separately defined with their own composition limits in the present patent application, they are not within the definition of “incidental elements” for the purposes of the present patent application.

[0045] As noted above, the new alloys may include the stated alloying ingredients, the balance being cobalt, optional incidental elements, and impurities. As used herein, “incidental elements” includes grain boundary modifiers, casting aids, and/or grain structure control materials, such as zirconium, hafnium, and the like, that may be used in the alloy. For instance, one or more of zirconium, hafnium, and the like may be added in an amount sufficient to provide grain boundary modification. The amount added should be restricted to an amount sufficient to provide grain boundary modification without inappropriately degrading properties of the material, such as by intermetallic formation. As one non-limiting example, up to 0.5 wt. % Hf and up to 0.5 wt. % Zr may be added to the material, provided the amount added does not result in inappropriate degradation of material properties. Incidental elements may be present in minor amounts, or may be present in significant amounts, and may add desirable or other characteristics on their own without departing from the alloy described herein, so long as the alloy retains the desirable characteristics described herein. It is to be understood, however, that the scope of this disclosure should not/cannot be avoided through the mere addition of an element or elements in quantities that would not otherwise impact on the combinations of properties desired and attained herein.

II. Microstructure

[0046] As noted above, the new cobalt-based alloys may realize an improved combination of properties, such as an improved combination of two or more of density, strength, ductility, oxidation resistance, and a narrow non-equilibrium freezing range, among others. An improved combination of properties may be realized, for instance, due to the microstructure of the new cobalt-based alloys. In one embodiment, the new cobalt-based alloys may realize a dual phase microstructure. For instance, the new cobalt-alloys may realize a face-centered cubic (fee) + body-centered cubic/B2 microstructure. The bcc and/or B2 phases may facilitate strengthening to the new cobalt-based alloys at elevated temperature (e.g., from 700 to 1 l75°C). In one embodiment, a new cobalt-based alloy realizes a dual phase microstructure at a temperature of at least 700°C. In another embodiment, a new cobalt-based alloy realizes a dual phase microstructure at a temperature of at least 750°C. In yet another embodiment, a new cobalt-based alloy realizes a dual phase micro structure at a temperature of at least 800°C. In one embodiment, a new cobalt-based alloy realizes a dual phase microstructure at not greater than 1 l75°C.

[0047] In one embodiment, a new cobalt-based alloy includes at least 1 vol. % of B2 phase. In another embodiment, a new cobalt-based alloy includes at least 5 vol. % of B2 phase. In yet another embodiment, a new cobalt-based alloy includes at least 10 vol. % of B2 phase. In yet another embodiment, a new cobalt-based alloy includes at least 15 vol. % of B2 phase. In one embodiment, a new cobalt-based alloy includes not greater than 35 vol. % of B2 phase. In another embodiment, a new cobalt-based alloy includes not greater than 30 vol. % of B2 phase. In yet another embodiment, a new cobalt-based alloy includes not greater than 25 vol. % of B2 phase. In some of the above embodiments, the vol. % of B2 phase is present at a temperature of at least 700°C. In some of the above embodiments, the vol. % of B2 phase is present at a temperature of at least 800°C. In some of the above embodiments, the vol. % of B2 phase is present at a temperature of not greater than 1 l00°C. In some of the above embodiments, the vol. % of B2 phase is present at a temperature of not greater than l000°C. In some of the above embodiments, the vol. % of B2 phase is present at a temperature of not greater than 900°C.

[0048] As used herein,“vol. % of B2 phase” is determined by implementing a measured cobalt-based alloy composition in a Scheil solidification calculation using the calculation of phase diagram (“CALPHAD”) computer software PANDAT® 2016 (dated November 11, 2016), and employing the PanCo20l6 database (dated November 11, 2016).

[0049] The new cobalt-based alloys may include precipitates (e.g., precipitation of B2 phase after solutionizing), and the precipitates may have a high solvus temperature. In one embodiment, a precipitate (e.g., B2 phase) has a solvus temperature of at least H75°C. In another embodiment, a precipitate (e.g., B2 phase) has a solvus temperature of at least l225°C. In yet another embodiment, a precipitate (e.g., B2 phase) has a solvus temperature of at least l275°C. The precipitates may be strengthening precipitates. In one embodiment, a precipitate has a solvus temperature that is at least l0°C below the solidus temperature (e.g., for solutionizing).

[0050] In some embodiments, a new cobalt-based alloy realizes a fine eutectic-type structure. As used herein, a“fine eutectic-type structure” means an alloy microstructure having regularly dispersed phases and comprising at least one of spheroidal, cellular, lamellar, wavy, brick and other suitable structures. The phases may be comprised of, for instance, body-centered cubic (bcc) phases, B2 phases, and/or intermetallics (e.g., intermetallics comprising at least one of Ni, Fe, Nb, Mo, and Ti), among others. In one embodiment, a fine eutectic-type structure comprises at least two of spheroidal, cellular, lamellar, wavy, brick or other suitable structures. In one embodiment, a fine eutectic-type structure comprises at least cellular structures.

[0051] In one embodiment, a new cobalt-based alloy product comprises a fine eutectic-type structure having an average spacing between eutectic structures (“average eutectic spacing”) of not greater than 10 micrometers. In another embodiment, the average eutectic spacing is not greater than 8 micrometers. In yet another embodiment, the average eutectic spacing is not greater than 6 micrometers. In another embodiment, the average eutectic spacing is not greater than 5 micrometers. In another embodiment, the average eutectic spacing is not greater than 4 micrometers. In yet another embodiment, the average eutectic spacing is not greater than 3 micrometers. In another embodiment, the average eutectic spacing is not greater than 2 micrometers. In yet another embodiment, the average eutectic spacing is not greater than 1 micrometers. In another embodiment, the average eutectic spacing is not greater than 0.5 micrometers.

[0052] As used herein,“average eutectic spacing” means the average spacing between the eutectic structures of the product as determined by the“Heyn Lineal Intercept Procedure” method described in ASTM standard El 12-13, entitled, “Standard Test Methods for Determining Average Grain Size”, wherein the distance between eutectic structures is/are measured as opposed to the grains.

[0053] In some embodiments, an additively manufactured cobalt-based alloy comprises equiaxed grains. Additively manufactured products that comprise equiaxed grains may realize, for instance, improved ductility and/or strength, among others. In this regard, equiaxed grains may facilitate the realization of improved ductility and/or strength, among others. In one embodiment, an additively manufactured cobalt-based alloy product comprises equiaxed grains, wherein the average grain size is of from 0.05 to 50 microns.

[0054] As used herein,“equiaxed grains” means grains having an average aspect ratio of less than 4: 1 as measured in the XY, YZ, and XZ planes. The“aspect ratio” is determined using commercial software Edax OIM version 8.0 or equivalent. The commercial software fits an ellipse to the perimeter points of the grain. As used herein,“aspect ratio” is the inverse of: the length of the minor axis of the ellipse divided by the length of the major axis of the ellipse as determined using commercial software. In one embodiment, an additively manufactured cobalt-based alloy part comprises equiaxed grains having an average aspect ratio of less than 4: 1. In one embodiment, an additively manufactured cobalt-based alloy part comprises equiaxed grains having an average aspect ratio of not greater than 3 : 1. In one described embodiment, an additively manufactured cobalt-based alloy part comprises equiaxed grains having an average aspect ratio of not greater than 2: 1. In one embodiment, an additively manufactured cobalt-based alloy part comprises equiaxed grains having an average aspect ratio of not greater than 1.5: 1. In one embodiment, an additively manufactured cobalt-based alloy part comprises equiaxed grains having an average aspect ratio of not greater than 1.1 : 1. The amount (volume percent) of equiaxed grains in the additively manufactured product in the as- built condition may be determined by EBSD (electron backscatter diffraction) analysis of a suitable number of SEM micrographs of the additively manufactured- product in the as-built condition. Generally, at least 5 micrographs should be analyzed.

[0055] The average size of equiaxed grains of the additively manufactured cobalt-based alloy product may be not greater than 50 microns. In one embodiment, the average size of the equiaxed grains of the additively manufactured cobalt-based alloy product is not greater than 40 microns. In another embodiment, the average size of the equiaxed grains of the additively manufactured cobalt-based alloy product is not greater than 30 microns. In yet another embodiment, the average size of the equiaxed grains of the additively manufactured cobalt- based alloy product is not greater than 20 microns. In another embodiment, the average size of the equiaxed grains of the additively manufactured cobalt-based alloy product is not greater than 10 microns. In yet another embodiment, the average size of the equiaxed grains of the additively manufactured cobalt-based alloy product is not greater than 5 microns. In another embodiment, the average size of the equiaxed grains of the additively manufactured cobalt- based alloy product is not greater than 4 microns. In yet another embodiment, the average size of the equiaxed grains of the additively manufactured cobalt-based alloy product is not greater than 3 microns. In another embodiment, the average size of the equiaxed grains of the additively manufactured cobalt-based alloy product is not greater than 2 microns, or less. In any of these embodiments, the equiaxed grains may be realized in the as-built condition.

[0056] In one embodiment, an additively manufactured cobalt-based alloy product comprises grains and at least 50 vol. % of the grains are equiaxed grains. In another embodiment, an additively manufactured cobalt-based alloy product comprises at least 60 vol. % of equiaxed grains. In yet another embodiment, an additively manufactured cobalt-based alloy product comprises at least 70 vol. % of equiaxed grains. In another embodiment, an additively manufactured cobalt-based alloy product comprises at least 80 vol. % of equiaxed grains. In yet another embodiment, an additively manufactured cobalt-based alloy product comprises at least 90 vol. % of equiaxed grains. In another embodiment, an additively manufactured cobalt- based alloy product comprises at least 95 vol. % of equiaxed grains. In yet another embodiment, an additively manufactured cobalt-based alloy product comprises at least 99 vol. % of equiaxed grains, or more. In any of these embodiments, the equiaxed grains may be realized in the as-built condition.

[0057] As used herein, the “as-built condition” means the condition of the additively manufactured cobalt-based alloy product after production and absent of any subsequent mechanical, thermal or thermomechanical treatments.

[0058] As used herein,“grain” takes on the meaning defined in ASTM El 12 §3.2.2, i.e.,“the area within the confines of the original (primary) boundary observed on the two-dimensional plane of-polish or that volume enclosed by the original (primary) boundary in the three- dimensional object”.

[0059] As used herein, the“grain size” is calculated by the following equation:

v/ = square root (—)

• wherein A i is the area of the individual grain as measured using commercial software Edax OIM version 8.0 or equivalent; and

• wherein vi is the calculated individual grain size assuming the grain is a circle. Grain size is determined based on a two-dimensional plane that includes the build direction of the additively manufactured product.

[0060] As used herein, the“area weighted average grain size” is calculated by the following equation:

v-bar

• wherein Ai is the area of each individual grain as measured using commercial software Edax OIM version 8.0 or equivalent;

• wherein vi is the calculated individual grain size assuming the grain is a circle; and

• wherein v-bar is the area weighted average grain size.

III. Properties

[0061] As noted above, the new cobalt-based alloys may realize an improved combination of properties, such as an improved combination of two or more of density, strength, ductility, oxidation resistance, and a narrow non-equilibrium freezing range, among others. For instance, the new cobalt-based alloys may realize a narrow non-equilibrium freezing range. In one embodiment, a new cobalt-based alloy realizes a non-equilibrium freezing range of not greater than l50°C. In another embodiment, a new cobalt-based alloy realizes a non-equilibrium freezing range of not greater than l00°C. In yet another embodiment, a new cobalt-based alloy realizes a non-equilibrium freezing range of not greater than 75°C, or lower.

[0062] The new cobalt-based alloys may realize a low density. In one embodiment, a new cobalt-based alloy realizes a density of not greater than 8.4 g/cc. In another embodiment, a new cobalt-based alloy realizes a density of not greater than 8.3 g/cc. In yet another embodiment, a new cobalt-based alloy realizes a density of not greater than 8.2 g/cc. In another embodiment, a new cobalt-based alloy realizes a density of not greater than 8.1 g/cc, or lower.

[0063] The new cobalt-based alloys may realize good oxidation resistance (e.g., due to the formation of an AI2O3 layer on the alloy’s surface, which may prevent further diffusion of oxygen into the bulk material). For instance, the new cobalt-based alloys may realize good oxidation at elevated temperature. In one embodiment, a cobalt-based alloy includes an AI2O3 layer at least partially covering its surface. In another embodiment, a cobalt-based alloy includes an AI2O3 layer covering the entirety of its surface. Chromium oxides (e.g., CnCb) may also be present in the oxide layer and may facilitate corrosion resistance. A layer of AI2O3 may facilitate improved corrosion resistance relative to other cobalt-based alloys having no aluminum. In one embodiment, a new cobalt-based alloy (as described herein) realizes a corrosion resistance that is equivalent to, or better than, the corrosion resistance required by ASTM Standard F75-12 for Cobalt-28 Chromium-6 Molybdenum Alloy Castings and Casting Alloy for Surgical Implants. In this regard, the AI2O3 layer may be realized after a thermal exposure in the presence of oxygen at elevated temperature. The thermal exposure may be, for instance, a solution heat treatment step, and/or an annealing step, among others. As another non-limiting example, an AI2O3 layer may form during operation of a final cobalt-based alloy product.

[0064] In one embodiment, a new cobalt-based alloy realizes a determined metal loss of not greater than 500 microns, as defined below. In another embodiment, a new cobalt-based alloy realizes a determined metal loss of not greater than 450 microns. In yet another embodiment, a new cobalt-based alloy realizes a determined metal loss of not greater than 400 microns. In another embodiment, a new cobalt-based alloy realizes a determined metal loss of not greater than 350 microns. In yet another embodiment, a new cobalt-based alloy realizes a determined metal loss of not greater than 300 microns. In another embodiment, a new cobalt-based alloy realizes a determined metal loss of not greater than 250 microns. In yet another embodiment, a new cobalt-based alloy realizes a determined metal loss of not greater than 200 microns. In another embodiment, a new cobalt-based alloy realizes a determined metal loss of not greater than 150 microns. In yet another embodiment, a new cobalt-based alloy realizes a determined metal loss of not greater than 100 microns. In some embodiments, the determined metal loss is realized after testing the cobalt-based alloy in an as-built condition. In some embodiments, the determined metal loss is realized in a surface-treated condition (e.g., post-machining, post- polishing). In some embodiments, the determined metal loss is realized after testing the cobalt- based alloy in a thermally treated condition.

[0065] As used herein,“determined metal loss” is determined by all of:

1. Exposing a cobalt-based alloy sample to flowing air at a velocity of 213 cm/min at 1 l50°C for one week;

2. Cooling the cobalt-based alloy sample to room temperature at the end of the one week;

3. Removing three portions of the cobalt-based alloy sample, where the three portions are sufficient in size to produce a micrograph of the surface of the sample;

4. Producing three micrographs from the portion of the sample in step 3;

5. Measuring the metal loss (in microns) using the three micrographs from step 4 in accordance with FIG. 3, and averaging the three metal loss values; and

6. Repeating steps 1-5 until the average metal loss from step 5 is within 5% of the average metal loss from the previous week. The determined metal loss is the averaged value from the last three samples measured that is within 5% of the average metal loss from the previous week.

[0066] The new cobalt-based alloys may realize good strength properties. In one embodiment, a new cobalt-based alloy (as described herein) realizes a strength (e.g., TYS, UTS) that is equivalent to, or better than, the strength required by ASTM Standard F75-12 for Cobalt-28 Chromium-6 Molybdenum Alloy Castings and Casting Alloy for Surgical Implants. In one embodiment, a new cobalt-based alloy realizes a UTS (L) of at least 600 MPa at room temperature. In another embodiment, a new cobalt-based alloy realizes a UTS (L) of at least 625 MPa at room temperature. In yet another embodiment, a new cobalt-based alloy realizes a UTS (L) of at least 650 MPa at room temperature. In another embodiment, a new cobalt- based alloy realizes a UTS (L) of at least 675 MPa at room temperature. In yet another embodiment, a new cobalt-based alloy realizes a UTS (L) of at least 700 MPa at room temperature. In another embodiment, a new cobalt-based alloy realizes a UTS (L) of at least 725 MPa at room temperature. In one embodiment, a new cobalt-based alloy realizes a TYS (L) of at least 300 MPa at room temperature. In another embodiment, a new cobalt-based alloy realizes a TYS (L) of at least 320 MPa at room temperature. In yet another embodiment, a new cobalt-based alloy realizes a TYS (L) of at least 340 MPa at room temperature. In another embodiment, a new cobalt-based alloy realizes a TYS (L) of at least 350 MPa at room temperature. The new cobalt-based alloys may realize good ductility. In one embodiment, a new cobalt-based alloy realizes an elongation of at least 8% (L) at room temperature. In another embodiment, a new cobalt-based alloy realizes an elongation of at least 9% (L) at room temperature. In another embodiment, a new cobalt-based alloy realizes an elongation of at least 10% (L) at room temperature. In one embodiment, the tensile properties are tested in accordance with ASTM E8.

[0067] In one embodiment, an additively manufactured cobalt-based alloy realizes a TYS of at least 700 MPa in the as-built condition at room temperature. In another embodiment, an additively manufactured cobalt-based alloy realizes a TYS of at least 725 MPa in the as-built condition at room temperature. In yet another embodiment, an additively manufactured cobalt- based alloy realizes a TYS of at least 750 MPa in the as-built condition at room temperature. In another embodiment, an additively manufactured cobalt-based alloy realizes a TYS of at least 775 MPa in the as-built condition at room temperature. In yet another embodiment, an additively manufactured cobalt-based alloy realizes a TYS of at least 800 MPa in the as-built condition at room temperature. In another embodiment, an additively manufactured cobalt- based alloy realizes a TYS of at least 825 MPa in the as-built condition at room temperature. In one embodiment, an additively manufactured cobalt-based alloy realizes a UTS of at least 900 MPa in the as-built condition at room temperature. In another embodiment, an additively manufactured cobalt-based alloy realizes a UTS of at least 925 MPa in the as-built condition at room temperature. In yet another embodiment, an additively manufactured cobalt-based alloy realizes a UTS of at least 950 MPa in the as-built condition at room temperature. In another embodiment, an additively manufactured cobalt-based alloy realizes a UTS of at least 975 MPa in the as-built condition at room temperature. In another embodiment, an additively manufactured cobalt-based alloy realizes a UTS of at least 1000 MPa in the as-built condition at room temperature. In one embodiment, an additively manufactured cobalt-based alloy realizes an elongation of at least 4% in the as-built condition at room temperature. In another embodiment, an additively manufactured cobalt-based alloy realizes an elongation of at least 5% in the as-built condition at room temperature. In yet another embodiment, an additively manufactured cobalt-based alloy realizes an elongation of at least 6% in the as-built condition at room temperature. In one embodiment, the tensile properties are tested in accordance with ASTM E8.

[0068] In one embodiment, an additively manufactured cobalt-based alloy realizes a TYS of at least 425 MPa in the as-built condition at 650°C (i.e., the additively manufactured cobalt- based alloy is produced and then tested at 650°C). In another embodiment, an additively manufactured cobalt-based alloy realizes a TYS of at least 450 MPa in the as-built condition at 650°C. In yet another embodiment, an additively manufactured cobalt-based alloy realizes a TYS of at least 475 MPa in the as-built condition at 650°C. In another embodiment, an additively manufactured cobalt-based alloy realizes a TYS of at least 500 MPa in the as-built condition at 650°C. In one embodiment, an additively manufactured cobalt-based alloy realizes a UTS of at least 600 MPa in the as-built condition at 650°C. In another embodiment, an additively manufactured cobalt-based alloy realizes a UTS of at least 650 MPa in the as- built condition at 650°C. In yet another embodiment, an additively manufactured cobalt-based alloy realizes a UTS of at least 700 MPa in the as-built condition at 650°C. In another embodiment, an additively manufactured cobalt-based alloy realizes a UTS of at least 750 MPa in the as-built condition at 650°C. In one embodiment, an additively manufactured cobalt- based alloy realizes an elongation of at least 12% in the as-built condition at 650°C. In another embodiment, an additively manufactured cobalt-based alloy realizes an elongation of at least 14% in the as-built condition at 650°C. In yet another embodiment, an additively manufactured cobalt-based alloy realizes an elongation of at least 16% in the as-built condition at 650°C. In one embodiment, the tensile properties are tested in accordance with ASTM E21.

IV. Product Forms and Processing

[0069] The new cobalt-based alloys may be made via any suitable processing route. Furthermore, any suitable processing route may facilitate the production of crack-free cobalt- based alloy products. In one embodiment, the new cobalt-based alloys are in a cast form such as in the form of an ingot or billet (e.g., for producing wrought products). In one embodiment, a new cobalt-based alloy product is a crack-free ingot or billet. In one embodiment, a new cobalt-based alloy product is a crack-free wrought product. A wrought product may be one of a rolled product, an extruded product, or a forged product, among others. In one embodiment, the processing route involves rapid solidification, such as high-pressure die casting and some continuous castings techniques. In one embodiment, a new cobalt-based alloy product is a crack-free shape-cast (foundry) product. In one embodiment, the new cobalt-based alloys are in the form of powders or wires (e.g., for use in an additive manufacturing process). In one embodiment, a powder of the new cobalt-based alloys is used to produce a powder metallurgy product. In one embodiment, a new cobalt-based alloy product is a crack-free powder metallurgy product. In one embodiment, a new cobalt-based alloy product is a crack-free additively manufactured product. In one embodiment, a new cobalt-based alloy is an additive manufacturing feedstock.

[0070] In some embodiments,“crack-free” means that the product is sufficiently free of cracks such that it can be used for its intended, end-use purpose. The determination of whether a product is“crack-free” may be made by any suitable method, such as, by visual inspection, dye penetrant inspection, and/or by non-destructive test methods. In some embodiments, the non destructive test method is an ultrasonic inspection. In some embodiments, the non-destructive test method is a computed topography scan (“CT scan”) inspection (e.g., by measuring density differences within the product). In one embodiment, a cobalt-based alloy product is determined to be crack-free by visual inspection. In another embodiment, a cobalt-based alloy product is determined to be crack-free by dye penetrant inspection. In yet another embodiment, a cobalt- based alloy product is determined to be crack-free by CT scan inspection, as evaluated in accordance with ASTM E1441. In another embodiment, a cobalt-based alloy product is determined to be crack-free during an additive manufacturing process, wherein in situ monitoring of the additively manufactured build is employed.

[0071] As noted above, the new cobalt-based alloys may be prepared into wrought form. The new cobalt-based alloys may be prepared into wrought form by more or less conventional practices, including direct chill (DC) casting the cobalt-based alloy into ingot form. After conventional scalping, lathing or peeling (if needed) and homogenization, which homogenization may be completed before or after scalping, these ingots may be further processed by hot working the product. The product may then be optionally cold worked, optionally annealed, and/or solution heat treated.

[0072] In one embodiment, the new cobalt-based alloys are additively manufactured. In one embodiment, a new cobalt-based alloy product is a crack-free additively manufactured product. As used herein,“additive manufacturing” means,“a process of joining materials to make objects from 3D model data, usually layer upon layer, as opposed to subtractive manufacturing methodologies”, as defined in ASTM F2792-l2a entitled “Standard Terminology for Additively Manufacturing Technologies”. Additively manufactured cobalt-based alloy bodies may be manufactured via any appropriate additive manufacturing technique described in this ASTM standard, such as binder jetting, directed energy deposition, material extrusion, material jetting, powder bed fusion, or sheet lamination, among others. Any suitable feedstocks may be used, including one or more powders, one or more wires, one or more sheets, and combinations thereof. In some embodiments the additive manufacturing feedstock is comprised of one or more powders. In some embodiments, the additive manufacturing feedstock is comprised of one or more wires. In some embodiments, the additive manufacturing feedstock is comprised of one or more sheets. Foil is a type of sheet. In one embodiment, the new cobalt-based alloys are in the form of sheets (e.g., foils) for use in additive manufacturing processes such as sheet lamination, per ASTM F2792-l2a.

[0073] In one embodiment, an additive manufacturing process includes depositing successive layers of one or more powders and then selectively melting and/or sintering the powders to create, layer-by-layer, an additively manufactured cobalt-based alloy body (product). In one embodiment, an additive manufacturing processes uses one or more of Selective Laser Sintering (SLS), Selective Laser Melting (SLM), and Electron Beam Melting (EBM), among others. In one embodiment, an additive manufacturing process uses an EOSINT M 280 Direct Metal Laser Sintering (DMLS) additive manufacturing system, or comparable system, available from EOS GmbH (Robert-Stirling-Ring 1, 82152 Krailling/Munich, Germany). In one embodiment, additive manufacturing process uses a LENS additive manufacturing system, or comparable system, available from OPTOMEC, 3911 Singer N.E., Albuquerque, NM 87109.

[0074] As one example, a feedstock, such as a powder or wire, comprising (or consisting essentially of) any of the cobalt-based alloy compositions described above may be used in an additive manufacturing apparatus to produce an additively manufactured cobalt-based alloy body. In some embodiments, the additively manufactured cobalt-based alloy body is a crack- free preform. The feedstock may be selectively heated above the liquidus temperature of the material, thereby forming a molten pool having any of the cobalt-based alloy compositions described above, followed by rapid solidification of the molten pool thereby forming an additively manufactured cobalt-based alloy product.

[0075] As noted above, additive manufacturing may be used to create, layer-by-layer, the cobalt-based alloy product. In one embodiment, a metal powder bed is used to create a tailored cobalt-based alloy product. As used herein a“metal powder bed” means a bed comprising a metal powder. During additive manufacturing, particles of the same or different compositions may melt (e.g., rapidly melt) and then solidify (e.g., in the absence of homogenous mixing). Thus, products having a homogenous or non-homogeneous microstructure may be produced. One embodiment of a method of making an additively manufactured cobalt-based alloy body may include (a) dispersing a powder having any of the cobalt-based alloy compositions described above, (b) selectively heating a portion of the powder (e.g., via a laser) to a temperature above the liquidus temperature of the particular body to be formed, (c) forming a molten pool having any of the cobalt-based alloy compositions described above, and (d) cooling the molten pool at a cooling rate of at least l000°C per second. In one embodiment, the cooling rate is at least l0,000°C per second. In another embodiment, the cooling rate is at least l00,000°C per second. In another embodiment, the cooling rate is at least l,000,000°C per second. Steps (a)-(d) may be repeated as necessary until the cobalt-based alloy body is completed, i.e., until the final additively manufactured cobalt-based alloy body is formed / completed. The final additively manufactured cobalt-based alloy body may be of a complex geometry, or may be of a simple geometry (e.g., in the form of a sheet or plate). After or during production, an additively manufactured cobalt-based alloy product may be deformed (e.g., by one or more of rolling, extruding, forging, stretching, compressing).

[0076] The powders used to additively manufacture a cobalt-based alloy body may be produced by atomizing a material (e.g., an ingot or melt) of the new alloy cobalt-based alloys into powders of the appropriate dimensions relative to the additive manufacturing process to be used. As used herein,“powder” means a material comprising a plurality of particles. Powders may be used in a powder bed to produce a tailored alloy product via additive manufacturing. In one embodiment, the same general powder is used throughout the additive manufacturing process to produce a cobalt-based alloy product. For instance, the final tailored cobalt-based alloy product may comprise a single region / matrix produced by using generally the same metal powder during the additive manufacturing process. The final tailored cobalt- based alloy product may alternatively comprise at least two separately produced distinct regions. In one embodiment, different metal powder bed types may be used to produce the cobalt-based alloy product. For instance, a first metal powder bed may comprise a first metal powder and a second metal powder bed may comprise a second metal powder, different than the first metal powder. The first metal powder bed may be used to produce a first layer or portion of the cobalt-based alloy product, and the second metal powder bed may be used to produce a second layer or portion of the cobalt-based alloy product. As used herein, a“particle” means a minute fragment of matter having a size suitable for use in the powder of the powder bed (e.g., a size of from 5 microns to 100 microns). Particles may be produced, for example, via atomization (e.g., gas atomization, plasma atomization).

[0077] The additively manufactured cobalt-based alloy body may be subj ect to any appropriate working steps. If employed, the working steps may be conducted on an intermediate form of the additively manufactured body and/or may be conducted on a final form of the additively manufactured body. In one embodiment, an additively manufactured body consists essentially of any of the cobalt-based alloy compositions described above.

[0078] In another embodiment, a cobalt-based alloy body is a preform for subsequent working. A preform may be an additively manufactured product. In one embodiment, a preform is of a near net shape product that is close to the final desired shape of the final product, but the preform is designed to allow for subsequent working to achieve the final product shape. Thus, the preform may worked such as by forging, rolling, extrusion, or hipping to produce an intermediate product or a final product, which intermediate or final product may be subject to any further appropriate working or thermal steps (e.g., stress relief), as described above, to achieve the final product. In one embodiment, the working comprises hot isostatic pressing (HIP) to compress the part. In one embodiment, a cobalt-based alloy preform may be compressed and porosity may be reduced. In one embodiment, the HIP temperature is maintained below the incipient melting point of the cobalt-based alloy preform. In one embodiment, the preform may be a near net shape product.

[0079] In one approach, electron beam (EB) or plasma arc techniques are utilized to produce at least a portion of the additively manufactured cobalt-based alloy body. Electron beam techniques may facilitate production of larger parts than readily produced via laser additive manufacturing techniques. In one embodiment, a method comprises feeding a wire (e.g., < 5 mm in diameter) of the new cobalt-based alloys described herein to the wire feeder portion of an electron beam gun. The wire may be of any of the compositions described above. The electron beam (EB) heats the wire above the liquidus point of the body to be formed, followed by rapid solidification (e.g., at least l00°C per second) of the molten pool to form the deposited material. The wire could be fabricated by a conventional ingot process or by a powder consolidation process. These steps may be repeated as necessary until the final cobalt-based alloy body is produced. Plasma arc wire feed may similarly be used with the cobalt-based alloys disclosed herein. In one embodiment, not illustrated, an electron beam (EB) or plasma arc additive manufacturing apparatus may employ multiple different wires with corresponding multiple different radiation sources, each of the wires and sources being fed and activated, as appropriate to provide the cobalt-based alloy product.

[0080] In another approach, a method may comprise (a) selectively spraying one or more metal powders of the new cobalt-based alloys described herein towards a building substrate, (b) heating, via a radiation source, the metal powders, and optionally the building substrate, above the liquidus temperature of the product to be formed, thereby forming a molten pool, (c) cooling the molten pool, thereby forming a solid portion of the product, wherein the cooling comprises cooling at a cooling rate of at least l00°C per second. In one embodiment, the cooling rate is at least l000°C per second. In another embodiment, the cooling rate is at least l0,000°C per second. The cooling step (c) may be accomplished by moving the radiation source away from the molten pool and/or by moving the building substrate having the molten pool away from the radiation source. Steps (a)-(c) may be repeated as necessary until the product is completed. The spraying step (a) may be accomplished via one or more nozzles, and the composition of the metal powders can be varied, as appropriate, to provide a tailored final cobalt-based alloy product. The composition of the metal powder being heated at any one time can be varied in real-time by using different powders in different nozzles and/or by varying the powder composition(s) provided to any one nozzle in real-time. The work piece can be any suitable substrate. In one embodiment, the building substrate is, itself, a metal product (e.g., an alloy product, such as any of the cobalt-based alloy products described herein.)

V. Product Applications

[0081] The new cobalt-based alloys described above may be suitable for elevated temperature applications. For instance, the new cobalt-based alloy bodies of the new cobalt-based alloys described herein may be suitable in aerospace and/or automotive applications. In one embodiment, a new cobalt-based alloy is used in a ground transportation application. Non limiting examples of aerospace applications may include heat exchangers and turbines (e.g., turbocharger impeller wheels). Non-limiting examples of automotive applications may include interior or exterior trim/appliques, pistons, valves, and/or turbochargers. Other examples include any components close to a hot area of the vehicle, such as engine components and/or exhaust components, such as the manifold.

[0082] Aside from the applications described above, the new cobalt-based alloy bodies of the present disclosure may also be utilized in a variety of consumer products, such as any consumer electronic products, including laptops, cell phones, cameras, mobile music players, handheld devices, computers, televisions, microwave, cookware, washer/dryer, refrigerator, sporting goods, or any other consumer electronic product requiring durability and selective visual appearance. In one embodiment, the visual appearance of the consumer electronic product meets consumer acceptance standards.

[0083] In some embodiments, the new cobalt-based alloy bodies of the present disclosure may be utilized in a variety of products including non-consumer products including the likes of medical devices, transportation systems and security systems, to name a few. In other embodiments, the new cobalt-based alloy bodies may be incorporated in goods including the likes of car panels, media players, bottles and cans, office supplies, packages and containers, among others.

[0084] As noted above, the new cobalt-based alloys may be used in a variety of product applications. In this regard, at least a portion of a product (e.g., an additively manufactured product) may comprise any of the new cobalt-based alloy compositions described above. For instance, at least a portion of a cobalt-based alloy product may comprise one of the new cobalt- based alloy compositions, and at least one other portion may be comprised of a different material (e.g., a different cobalt-based alloy). Furthermore, the new cobalt-based alloy compositions may be present in a product comprising a compositional gradient (i.e., a graded product). At least a portion of a graded product may comprise any of the new cobalt-based alloy compositions described above.

[0085] The figures constitute a part of this specification and include illustrative embodiments of the present disclosure and illustrate various objects and features thereof. In addition, any measurements, specifications and the like shown in the figures are intended to be illustrative, and not restrictive. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the present invention.

[0086] Among those benefits and improvements that have been disclosed, other objects and advantages of this invention will become apparent from the following description taken in conjunction with the accompanying figures. Detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely illustrative of the invention that may be embodied in various forms. In addition, each of the examples given in connection with the various embodiments of the invention is intended to be illustrative, and not restrictive.

[0087] Throughout the specification and claims, the following terms take the meanings explicitly associated herein, unless the context clearly dictates otherwise. The phrases“in one embodiment” and“in some embodiments” as used herein do not necessarily refer to the same embodiment(s), though it may. Furthermore, the phrases“in another embodiment” and“in some other embodiments” as used herein do not necessarily refer to a different embodiment, although it may. Thus, as described below, various embodiments of the invention may be readily combined, without departing from the scope or spirit of the invention.

[0088] In addition, as used herein, the term "or" is an inclusive "or" operator, and is equivalent to the term "and/or," unless the context clearly dictates otherwise. The term "based on" is not exclusive and allows for being based on additional factors not described, unless the context clearly dictates otherwise. In addition, throughout the specification, the meaning of "a," "an," and "the" include plural references, unless the context clearly dictates otherwise. The meaning of "in" includes "in" and "on", unless the context clearly dictates otherwise.

BRIEF DESCRIPTION OF THE DRAWINGS

[0089] FIG. 1A is a scanning electron microscope (“SEM”) micrograph of Alloy 2 (as-built condition) of Example 1.

[0090] FIG. 1B is a higher magnification image of the micrograph of Alloy 2 shown in FIG. 1 A.

[0091] FIG. 2A is a SEM micrograph of Alloy 2 (heat-treated condition) of Example 1.

[0092] FIG. 2B is a higher magnification image of the micrograph of Alloy 2 shown in FIG. 2A.

[0093] FIG. 3 is a schematic diagram for calculating the determined mass loss of a cobalt- based alloy.

DETAILED DESCRIPTION

Example 1

[0094] A cobalt-based alloy was cast as an ingot (“Alloy 1”). The target composition of Alloy 1 was 5 wt. % Al, 27 wt. % Cr, with the balance being cobalt and impurities. After casting, the ingot was heat treated at l200°C for 6 hours in an argon atmosphere. After heat treating, one tensile testing specimen was machined from the heat-treated ingot. The tensile specimen was tested in accordance with ASTM E8, the results of which are shown in Table 1, below.

Table 1: Room Temperature Tensile Testing of Alloy 1

[0095] Another cobalt-based alloy having the same target composition as Alloy 1 was produced as powder via gas atomization (“Alloy 2”). After production of the Alloy 2 powder, several specimens were produced using an OPTOMEC® Laser Engineered Net Shaping (“LENS”) additive manufacturing apparatus. Prior to tensile testing, some of the specimens were heat treated at l200°C for 6 hours in an argon atmosphere, as indicated in Tables 2a-2b, below. Micrographs of Alloy 2 are shown in FIGS. 1A-1B (as-built condition) and 2A-2B (heat-treated condition), respectively. Room temperature tensile testing was conducted in accordance with ASTM E8, the results of which are shown in Table 2a, below. Elevated temperature (650°C) tensile testing of the tensile specimens was conducted in accordance with ASTM E21, the results of which are shown in Table 2b, below. Tensile testing was conducted in the XY-plane of the samples (i.e., a direction orthogonal to the build (Z) direction).

Table 2a: Room Temperature Tensile Testing of Alloy 2

Table 2b: Elevated Temperature (650°C) Tensile Testing of Alloy 2

[0096] As shown in FIGS. 1A-1B, the microstructure of Alloy 2 in the as-built condition comprises cellular structures (10). As shown in FIGS. 2A-2B, after a heat treatment at l200°C for 4 hours, Alloy 2 did not include these cellular structures. B2 precipitates (12), however, were observed in the heat-treated microstructure. While not being bound by any theory, it is believed that the boundaries of the cellular structures (10) in the as-built condition (FIGS. 1 A- 1B) are rich in aluminum-rich B2 phase. Further, it is believed that the boundaries of the cellular structures (10) from the as-built condition spherodized during heat-treatment to form the B2 precipitates (12) shown in FIGS. 2A-2B.

[0097] As shown in Tables 2a-2b, a decrease in the tensile yield strength (“TYS”) and ultimate tensile strength (“UTS”) was observed in the heat-treated specimens. While not being bound by any theory, it is believed that the decrease in the TYS and UTS occurred at least partially due to the spherodization of the cellular structures (10) described above. Thus, a less aggressive heat treatment method (e.g., lower temperature and/or lower periods of time) may be preferable for retaining strength, relative to the as-built condition.

[0098] While a number of embodiments of the present invention have been described, it is understood that these embodiments are illustrative only, and not restrictive, and that many modifications may become apparent to those of ordinary skill in the art. Further still, unless the context clearly requires otherwise, the various steps may be carried out in any desired order, and any applicable steps may be added and/or eliminated.

Claims

What is claimed is:

1. A cobalt-based alloy comprising:

from 26 to 30 wt. % Cr;

from 4 to 6 wt. % Al;

up to 20 wt. % Ni;

up to 5 wt. % Fe;

up to 3 wt. % Nb;

up to 3 wt. % Mo;

up to 5 wt. % W;

up to 2 wt. % Ti;

up to 0.5 wt. % C; and

up to 0.5 wt. % B.

2. The cobalt-based alloy of claim 1, wherein the cobalt-based alloy includes at least 45 wt. % Co, or at least 50 wt. % Co, or at least 55 wt. % Co, or at least 60 wt. % Co.

3. The cobalt-based alloy of any of the preceding claims, wherein the cobalt-based alloy includes not greater than 70 wt. % Co, or not greater than 68 wt. % Co.

4. The cobalt-based alloy of any of the preceding claims, wherein the cobalt-based alloy includes at least 27 wt. % Cr.

5. The cobalt-based alloy of any of the preceding claims, wherein the cobalt-based alloy includes not greater than 29 wt. % Cr.

6. The cobalt-based alloy of any of the preceding claims, wherein the cobalt-based alloy includes at least 4.5 wt. % Al.

7. The cobalt-based alloy of any of the preceding claims, wherein the cobalt-based alloy includes not greater than 5.5 wt. % Al.

8. The cobalt-based alloy of any of the preceding claims, wherein the cobalt-based alloy includes at least 0.5 wt. % Ni, or at least 1.0 wt. % Ni.

9. The cobalt-based alloy of any of the preceding claims, wherein the cobalt-based alloy includes not greater than 15 wt. % Ni, or not greater than 10 wt. % Ni, or not greater than 5 wt. % Ni.

10. The cobalt-based alloy of any of claims 1-7 and 9, wherein the cobalt-based alloy includes low amounts of nickel, having less than 0.5 wt. % Ni.

11. The cobalt-based alloy of any of the preceding claims, wherein the cobalt-based alloy includes at least 0.5 wt. % Fe, or at least 1.0 wt. % Fe, or at least 1.0 wt. % Fe, or at least 1.5 wt. % Fe, or at least 2.0 wt. % Fe, or at least 2.5 wt. % Fe, or at least 3.0 wt. % Fe.

12. The cobalt-based alloy of any of claims 1-10, wherein the cobalt-based alloy includes low amounts of iron, having less than 0.5 wt. % Fe.

13. The cobalt-based alloy of any of the preceding claims, wherein the cobalt-based alloy includes at least 0.5 wt. % Nb, or at least 1.0 wt. % Nb, or at least 2.0 wt. % Nb.

14. The cobalt-based alloy of any of claims 1-12, wherein the cobalt-based alloy includes low amounts of niobium, having less than 0.5 wt. % Nb.

15. The cobalt-based alloy of any of the preceding claims, wherein the cobalt-based alloy includes at least 0.5 wt. % Mo, or at least 1.0 wt. % Mo, or at least 1.5 wt. % Mo, or at least 2.0 wt. % Mo.

16. The cobalt-based alloy of any of the preceding claims, wherein the cobalt-based alloy includes not greater than 2.5 wt. % Mo.

17. The cobalt-based alloy of any of claims 1-14 and 16, wherein the cobalt-based alloy includes low amounts of molybdenum, having less than 0.5 wt. % Mo.

18. The cobalt-based alloy of any of the preceding claims, wherein the cobalt-based alloy includes at least 0.5 wt. % W, or at least 1.0 wt. % W.

19. The cobalt-based alloy of any of the preceding claims, wherein the cobalt-based alloy includes not greater than 4 wt. % W, or not greater than 3 wt. % W, or not greater than 2 wt. % W.

21. The cobalt-based alloy of any of claims 1-17 and 19, wherein the cobalt-based alloy includes low amounts of tungsten, having less than 0.5 wt. % W.

22. The cobalt-based alloy of any of the preceding claims, wherein the total amount of niobium plus molybdenum plus tungsten in the cobalt-based alloy does not exceed 6 wt. %.

23. The cobalt-based alloy of any of the preceding claims, wherein the total amount of niobium plus molybdenum plus tungsten in the cobalt-based alloy does not exceed 5 wt. %, or does not exceed 4 wt. %.

24. The cobalt-based alloy of any of the preceding claims, wherein the cobalt-based alloy includes at least 0.2 wt. % Ti, or at least 0.5 wt. % Ti, or at least 1.0 wt. % Ti, or at least 1.5 wt. % Ti.

25. The cobalt-based alloy of any of claims 1-23, wherein the cobalt-based alloy includes low amounts of titanium, having less than 0.2 wt. % Ti.

26. The cobalt-based alloy of any of the preceding claims, wherein the cobalt-based alloy includes at least 0.01 wt. % C, or at least 0.05 wt. % C, or at least 0.10 wt. % C.

27. The cobalt-based alloy of any of the preceding claims, wherein the cobalt-based alloy includes not greater than 0.20 wt. % C.

28. The cobalt-based alloy of any of claims 1-25, wherein the cobalt-based alloy includes low amounts of carbon, having less than 0.01 wt. % C.

29. The cobalt-based alloy of any of the preceding claims, wherein the cobalt-based alloy includes at least 0.01 wt. % B, or at least 0.05 wt. % B.

30. The cobalt-based alloy of any of the preceding claims, wherein the cobalt-based alloy includes not greater than 0.20 wt. % B.

31. The cobalt-based alloy of any of claims 1-28, wherein the cobalt-based alloy includes low amounts of boron, having less than 0.01 wt. % B.

32. The cobalt-based alloy of any of the preceding claims, wherein the balance of the cobalt- based alloy is cobalt, any optional incidental elements, and unavoidable impurities.

33. The cobalt-based alloy of any of the preceding claims, wherein the cobalt-based alloy comprises a fine eutectic-type structure.

34. The cobalt-based alloy of claim 33, wherein the fine eutectic-type structure comprises at least cellular structures.

35. The cobalt-based alloy of any of claims 33-34, wherein the fine eutectic- structure realizes an average eutectic spacing of not greater than 10 micrometers, or not greater than 8 micrometers, or not greater than 6 micrometers, or not greater than 5 micrometers, or not greater than 4 micrometers, or not greater than 3 micrometers, or not greater than 2 micrometers, or not greater than 1 micrometers, or not greater than 0.5 micrometers.

36. The cobalt-based alloy of any of the preceding claims, wherein the cobalt-based alloy realizes a non-equilibrium freezing range of not greater than l50°C, or not greater than l00°C, or not greater than 75°C.

37. The cobalt-based alloy of any of the preceding claims, wherein the cobalt-based alloy realizes a density of not greater than 8.4 g/cc, or not greater than not greater than 8.3 g/cc, or not greater than 8.2 g/cc, or not greater than 8.1 g/cc.

38. The cobalt-based alloy of any of the preceding claims, wherein the cobalt-based alloy includes an AI2O3 layer at least partially covering its surface.

39. The cobalt-based alloy of claim 38, wherein the cobalt-based alloy realizes a determined metal loss of not greater than 500 microns, or not greater than 400 microns, or not greater than 350 microns, or not greater than 300 microns, or not greater than 250 microns, or not greater than 200 microns, or not greater than 150 microns, or not greater than 100 microns.

40. The cobalt-based alloy of any of the preceding claims, wherein the cobalt-based alloy realizes an fee plus B2 microstructure at a temperature of at least 700°C, or at least 750°C, or at least 800°C.

41. The cobalt-based alloy of claim 40, wherein the cobalt-based alloy realizes an fee plus B2 microstructure at a temperature of not greater than 1 l75°C.

42. The cobalt-based alloy of any of the preceding claims, wherein the cobalt-based alloy includes precipitates, and wherein at least some of the precipitates have a solvus temperature of at least 1 l75°C, or at least l225°C, or at least l275°C.

43. The cobalt-based alloy of any of the preceding claims, wherein the cobalt-based alloy includes at least 1 vol. % of B2 phase, or at least 5 vol. % of B2 phase, or at least 10 vol. % of B2 phase, or at least 15 vol. % of B2 phase.

44. The cobalt-based alloy of claim 43, wherein the cobalt-based alloy includes not greater than 35 vol. % of B2 phase, or not greater than 30 vol. % of B2 phase, or not greater than 25 vol. % of B2 phase.

45. The cobalt-based alloy of any of claims 43-44, wherein the vol. % of B2 is present at a temperature of at least 700°C, or at least 800°C.

46. The cobalt-based alloy of claim 45, wherein the vol. % of B2 is present at a temperature of not greater than 1 l00°C, or not greater than l000°C, or not greater than 900°C.

47. The cobalt-based alloy of any of the preceding claims, wherein the cobalt-based alloy is one of a wrought product, a shape-cast product, an ingot, a billet, an additively manufactured product, an additive manufacturing feedstock, or a powder metallurgy product.

48. The cobalt-based alloy of claim 47, wherein the cobalt-based alloy is an additively manufactured product.

49. The cobalt-based alloy of claim 48, wherein the cobalt-based alloy comprises equiaxed grains having an average grain size of from 0.5 to 50 microns.

50. The cobalt-based alloy of claim 49, wherein the cobalt-based alloy comprises at least 50 vol. % of the equiaxed grains, or at least 60 vol. % of the equiaxed grains, or at least 70 vol. % of the equiaxed grains, or at least 80 vol. % of the equiaxed grains, or at least 90 vol. % of the equiaxed grains, or at least 95 vol. % of the equiaxed grains, or at least 99 vol. % of the equiaxed grains.

51. The cobalt-based alloy of any of claims 49-50, wherein the equiaxed grains realize an average grain size of not greater than 30 microns, or not greater than 20 microns, or not greater than 10 microns, or not greater than 5 microns, or not greater than 4 microns, or not greater than 3 microns, or not greater than 2 microns.

52. The cobalt-based alloy of any of claims 48-51, wherein the additively manufactured product is in the as-built condition.

53. The cobalt-based alloy of any of the preceding claims, wherein the cobalt-based alloy is crack-free.