nickel-based alloy

Abstract

4.0 to 6.0 mass% aluminum, 1.1 to 6.0 mass% titanium, 0.0 to 4.0 mass% niobium, 0.0 to 11.9 mass% tantalum, 2.0 to 12.7 mass% tungsten, 0.0 to 3.0 mass% molybdenum, 0.0 to 22.0 mass% cobalt, 6.0 to 16.7 mass% chromium, 0.02 to 0.35 mass% carbon, 0.001 to 0.2 mass% boron, 0.00 to 0.01 mass% zirconium, 0.0 to 3.0 mass% rhenium, 0.0 to 3.0 mass% ruthenium, 0.0 to 3.0 mass% iridium, 0. A nickel-based alloy composition comprising 0 to 0.5 mass% vanadium, 0.0 to 1.0 mass% palladium, 0.0 to 1.0 mass% platinum, 0.0 to 0.5 mass% silicon, 0.0 to 0.1 mass% yttrium, 0.0 to 0.1 mass% lanthanum, 0.0 to 0.1 mass% cerium, 0.0 to 0.003 mass% sulfur, 0.0 to 0.25 mass% manganese, 0.0 to 0.1 mass% magnesium, 0.0 to 4.0 mass% iron, 0.0 to 0.5 mass% copper, 0.0 to 2.0 mass% hafnium, and the remainder being nickel and unavoidable impurities.

Description

[Technical Field]

[0001] The present invention relates to nickel-based superalloy compositions designed for application in additive manufacturing (AM) processes, including, but not limited to, powder-bed-based AM methods (e.g., selective laser melting, electron beam melting) and directed metal deposition methods (e.g., powder deposition and wire-based methods). [Background technology]

[0002] Currently, there is a trend to transfer nickel-based superalloys that have been successfully produced in cast or wrought forms to AM processes. However, this has proven largely inappropriate, as many of the material properties required to facilitate processing in AM processes are not met in the alloys mentioned above, resulting in materials that are significantly more difficult to process and that lack the expected structural integrity.

[0003] In particular, developing alloys with a high γ´ volume fraction for additive manufacturing processes has been a major challenge, as these alloys are often classified as “non-weldable.” Typically, these alloys are processed by investment casting. Examples of common alloys used in investment casting processes are listed in Table 1.

[0004] The alloys listed in Table 1 have been extensively studied for additive manufacturing (AM). Two of the most significant limitations of these alloys for use in AM processes are (i) their low high-temperature creep resistance compared to comparable cast materials, and (ii) their susceptibility to cracking during the AM process due to strain-age cracking and hot tearing.

[0005] It would be desirable to develop high volume fraction γ' alloys that overcome the limitations of the alloys in Table 1 by adjusting the alloy's chemical composition. Table 1 shows the nominal compositions, in mass percent, of conventional high γ' volume fraction alloys. [Table 1] Summary of the Invention [Problem to be solved by the invention]

[0006] A solution to at least one of the aforementioned problems with AM alloys has been discovered. In one aspect, this solution may include AM alloys with improved resistance to creep and / or strain age cracking. The AM alloys of the present invention preferably have desirable levels of tensile strength, freeze-out range, and hot-tearing resistance combined with acceptable oxidation resistance and / or microstructural stability. [Means for solving the problem]

[0007] According to the present invention, the aluminum content is 4.0 to 6.0% (e.g., 4.0, 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, 5.0, 5.1, 5.2, 5.3, 5.4, 5.5, 5.6, 5.7, 5.8, 5.9, or 6.0%, or any range or numerical value therein), and the aluminum content is 1.1 to 6.0% (e.g., 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0, 5.5, or 6.0%, or any range or numerical value therein), by mass. Titanium, 0.0-4.0% (e.g., 0.0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, or 4.0%, or any range or value therein), Niobium, 0.0-11.9% (e.g., 0.0, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0, 5.5, 6.0, 6.5, 7.0, 7.5, 8.0, 8.5, 9.0, 9.5, 10.0, 10.5, 11.0, 11.1, 11.2, 11.3, 11.4, 11.5, 11.6, 11.7, 11.8, 11.9, 12.10, 12.11, 12.12, 12.13, 12.14, 12.15, 12.16, 12.17, 12.18, 12.19, 13.20, 13.21, 13.22, 13.23, 13.24, 13.25, 13.26, 13.27, 13.28, 13.29, 13.30, 13.31, 13.32, 13.33, 13.34, 13.35, 13.36, 13.37, 13.38, 13. tantalum from 2.0 to 12.7% (e.g., 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0, 5.5, 6.0, 6.5, 7.0, 7.5, 8.0, 8.5, 9.0, 9.5, 10.0, 10.5, 11.0, 11.5, 12.0, 12.1, 12.2, 12.3, 12.4, 12.5, 12.6 or 12.7%, or any range or value therein); tungsten from 0.0 to 3.0% (e.g., 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 11.7, 11.8 or 11.9%, or any range or value therein); 0.0-22.0% (e.g., 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.5, 2.0, 2.5, or 3.0%, or any range or value therein) molybdenum; 0.0-22.0% (e.g., 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0, 9.0, 10.0, 11.0, 12.0, 13.0, 14.0, 15.0, 16.0, 17.0, 18.0, 19.0, 20.0, 21.0, or 22.0%, or any range or value therein) cobalt; 6.0-16.0% (e.g., 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0, 9.0, 10.0, 11.0, 12.0, 13.0, 14.0, 15.0, 16.0, 17.0, 18.0, 19.0, 20.0, 21.0, or 22.0%, or any range or value therein) cobalt;7% (e.g., 6.0, 7.0, 8.0, 9.0, 10.0, 11.0, 12.0, 13.0, 14.0, 15.0, 16.0, 16.1, 16.2, 16.3, 16.4, 16.5, 16.6, or 16.7%, or any range or numerical value therein) chromium, 0.02-0.35% (e.g., 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.10, 0.20, 0.30, 0.31, 0.32, 0.33, 0.34, or 0.35%, or any range or numerical value therein) carbon, 0.001 ~0.2% (e.g., 0.001, 0.002, 0.003, 0.004, 0.005, 0.006, 0.007, 0.008, 0.009, 0.01, 0.1, or 0.2%, or any range or value therein) boron, 0.00-0.01% zirconium, 0.0-3.0% (e.g., 0.0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 2.0, or 3.0%, or any range or value therein) rhenium, 0.0-3.0% (e.g., 0.0, 0.1, 0.2, 0.3, 0.4 , 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 2.0 or 3.0%, or any range or number therein) ruthenium, 0.0-3.0% (e.g., 0.0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 2.0 or 3.0%, or any range or number therein) iridium, 0.0-0.5% (e.g., 0.0, 0.1, 0.2, 0.3, 0.4 or 0.5%, or any range or number therein) vanadium, 0.0-1.0% (e.g., 0.0, 0.1, 0. 0.0-0.5% (e.g., 0.0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9 or 1.0%, or any range or value therein) palladium, 0.0-1.0% (e.g., 0.0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9 or 1.0%, or any range or value therein) platinum, 0.0-0.5% (e.g., 0.0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9 or 1.0%, or any range or value therein) silicon, 0.0-0.1% yttrium, 0.0-0.1% lanthanum, 0.0-0.1% cerium, 0.0-0.003% (e.g., 0.0, 0.001, 0.002, or 0.003%, or any range or value therein) sulfur, 0.0-0.25% (e.g., 0.0, 0.10, 0.20, or 0.25%, or any range or value therein) manganese, 0.0-0.1% magnesium, 0.0-4.0% (e.g., 0.0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 2.0, 3.0, or 4.0%) In one embodiment, a nickel-based alloy composition is provided that comprises: 0.0-0.5% (e.g., 0.0, 0.1, 0.2, 0.3, 0.4, or 0.5%, or any range or value therein) iron; 0.0-0.5% (e.g., 0.0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, or 2.0%, or any range or value therein) copper; 0.0-2.0% (e.g., 0.0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, or 2.0%, or any range or value therein) hafnium; and the balance being nickel and unavoidable impurities. In one particular embodiment, the nickel-based alloy composition can include greater than 0.05 wt. % carbon (e.g., 0.051, 0.052, 0.053, 0.054, 0.055, 0.056, 0.057, 0.058, 0.059, 0.06, 0.07, 0.08, 0.09, 0.1, 0.2, 0.3, or 0.35, or more, or any range or value therein).

[0008] These nickel-base alloys combine particularly high levels of creep resistance with high levels of AM processability. This combination of excellent properties is achieved through the simultaneous optimization of factors controlling creep (precipitation hardening (i.e., gamma-prime fraction), matrix phase strengthening (modeled by the creep figure of merit), and grain boundary strengthening (identified by the inventors for the first time for this class of alloys and described below)) and factors controlling AM processability (strain age cracking and hot tearing).

[0009] In one embodiment, the weight percent of niobium and tantalum in the alloy is W. Nb , W Ta Then, the following equation is satisfied: 0.60≦0.3WNb +0.15W Ta Preferably, the following formula is satisfied: 0.625≦0.3W Nb +0.15W Ta More preferably, the following formula is satisfied: 0.65≦0.3W Nb +0.15W Ta Such alloys have even better hot tear resistance.

[0010] In one embodiment, the weight percent of aluminum, titanium, niobium, and tantalum in the alloy is W. Al , W Ti , W Nb and W Ta Then, the following equation is satisfied: 5.6≦W Al +0.5W Ti +0.3W Nb +0.15W Ta ≦7.0 Preferably, the following formula is satisfied: 5.6≦W Al +0.5W Ti +0.3W Nb +0.15W Ta ≦6.5 Such alloys have improved resistance to strain age cracking.

[0011] In one embodiment, the weight percent of tungsten and molybdenum in the alloy is W W , W Mo Then, the following equation is satisfied: W W +0.65W Mo ≧4.0 Preferably, the following formula is satisfied: W W +0.65W Mo ≧6.0 More preferably, the following formula is satisfied: W W +0.65W Mo ≧8.0 Such alloys have improved creep resistance.

[0012] In one embodiment, the nickel-based alloy composition has, by weight, 8.0% or more chromium, preferably 8.5% or more chromium, more preferably 9.0% or more chromium, even more preferably 9.5% or more chromium, even more preferably 9.75% or more chromium, and most preferably 10.0% or more chromium, providing improved oxidation and corrosion resistance.

[0013] In one embodiment, the nickel-based alloy composition comprises 14.7% or less, preferably 13.8% or less, chromium, by weight, to provide improved microstructural stability.

[0014] In one embodiment, the nickel-based alloy composition comprises, by weight, 9.8% or less of tantalum, preferably 9.2% or less, more preferably 7.1% or less, even more preferably 6.3% or less, even more preferably 5.5% or less, even more preferably 5.0% or less, and most preferably 4.5% or less of tantalum. Such alloys have low density and can optionally contain increased tungsten content, which helps improve creep resistance.

[0015] In one embodiment, the nickel-based alloy composition has, by weight, 2.0% or less, preferably 1.8% or less, preferably 1.5% or less, more preferably 1.4% or less, and most preferably 1.3% or less molybdenum, which provides improved hot tearing resistance.

[0016] In one embodiment, the nickel-based alloy composition contains, by weight, 5.0% or less of titanium, preferably 4.2% or less, more preferably 3.0% or less, even more preferably 2.5% or less, even more preferably 2.0% or less, even more preferably 1.5% or less, even more preferably 1.4% or less, most preferably 1.3% or less, even more preferably 1.2% or less, or even more preferably 1.0-1.25%. Such alloys have better oxidation resistance.

[0017] In one embodiment, the nickel-based alloy composition comprises, by weight, 10.7% or less of tungsten, preferably 9.5% or less, more preferably 9.0% or less, even more preferably 8.7% or less, even more preferably 8.5% or less, most preferably 8.0% or less, and most preferably 7.5% or less of tungsten, which provides improved microstructural stability.

[0018] In one embodiment, the nickel-based alloy composition comprises, by weight, 3.0% or less, preferably 2.0% or less, of niobium, which provides improved oxidation resistance.

[0019] In one embodiment, the nickel-based alloy composition contains 0.5% or less of either or both of platinum and palladium, by weight percent, further reducing the cost of such alloys.

[0020] In one embodiment, the nickel-based alloy composition has an aluminum content, by weight, of at least 4.3%, preferably at least 4.5%, which provides improved corrosion resistance.

[0021] In one embodiment, the nickel-base alloy composition comprises, by weight, 5.6% or less of aluminum, preferably 5.5% or less, more preferably 5.3% or less, even more preferably 5.2% or less, and most preferably 5.1% or less of aluminum, which provides improved resistance to strain age cracking coupled with improved resistance to hot tearing.

[0022] In one embodiment, the nickel-based alloy composition comprises, by weight, 15.0% or less of cobalt, preferably 10.0% or less, more preferably 9.5% or less, and even more preferably 9.0% or less of cobalt, which reduces the freezing range of such alloys.

[0023] In one embodiment, the nickel-base alloy composition comprises, by weight, tantalum in an amount of at least 1.1%, preferably at least 2.0%, and more preferably at least 2.5%. In such alloys, the amount of niobium can be reduced without reducing hot-tearing resistance, or can be combined with higher levels of niobium to provide even greater improvements in hot-tearing resistance.

[0024] In one embodiment, the nickel-based alloy composition comprises, by weight, at least 2.7%, preferably at least 2.8%, more preferably at least 4.7%, even more preferably at least 5.1%, more preferably at least 5.2%, and most preferably at least 6.2% tungsten, which provides improved creep resistance.

[0025] In one embodiment, the weight percent of tantalum and tungsten in the alloy is W Ta and W W Then, the following equation is satisfied: W W +W Ta ≦13.9 Preferably, the following formula is satisfied: W W +W Ta ≦11.8 These alloys have a low density.

[0026] In one embodiment, the nickel-based alloy composition comprises, by weight, hafnium in an amount not greater than 1.5%, preferably not greater than 1.2%, and more preferably not greater than 1.1%.

[0027] The nickel-based alloy composition according to any one of claims 1 to 23, comprising, by mass %, 1.2% or more, preferably 1.3% or more, of titanium. Such an alloy is low in cost and has improved oxidation resistance. Such an alloy has improved creep resistance.

[0028] In one embodiment, the nickel-based alloy composition comprises, by weight, at least 0.1%, preferably at least 0.2%, more preferably at least 0.25%, even more preferably at least 0.3%, even more preferably at least 0.5%, and even more preferably at least 0.6% hafnium, providing improved creep and oxidation resistance.

[0029] In one embodiment, the nickel-based alloy composition comprises, by weight, 5.5% or more, preferably 6.0% or more, more preferably 8.0% or more, preferably 9.0% or more, more preferably 10.0% or more cobalt, resulting in a low gamma prime solvus.

[0030] In one embodiment, the nickel-based alloy composition has, by weight, niobium at least 0.05%, preferably at least 0.5%, and more preferably at least 1.0%, which provides the alloy with improved resistance to hot tearing.

[0031] In one embodiment, the nickel-based alloy composition comprises at least 0.1%, preferably 0.2%, and more preferably 0.5% molybdenum, by weight, providing higher tensile strength and creep resistance without a significant increase in density.

[0032] In one embodiment, the nickel-based alloy composition has, by weight, at most 0.005%, preferably at most 0.002%, and more preferably at most 0.0015% zirconium, which reduces the tendency of such alloys to hot tear.

[0033] In one embodiment, the nickel-based alloy composition has, by weight, 0.2% or less of carbon, preferably 0.15% or less, and more preferably 0.10% or less of carbon, making the alloy less susceptible to cracking.

[0034] In one embodiment, the nickel-based alloy composition has, by weight, at most 0.03%, preferably at most 0.02%, more preferably at most 0.018%, and most preferably at most 0.015% or even at most 0.012% boron, which provides improved creep resistance.

[0035] In one embodiment, the nickel-based alloy composition has at least 0.008% boron, by weight, which provides improved creep strength.

[0036] In one embodiment, the nickel-based alloy composition comprises, by weight, 2.9% or less of rhenium, preferably 2.5% or less, more preferably 2.0% or less, and most preferably 1.5% or less of rhenium, resulting in reduced costs.

[0037] In one embodiment, the nickel-based alloy composition comprises, by weight, at least 0.1%, preferably at least 0.2%, more preferably at least 0.3%, even more preferably at least 0.5%, and most preferably at least 0.8% rhenium, which provides improved strength, oxidation resistance, and microstructural stability.

[0038] In one embodiment, the nickel-based alloy composition has, by weight, 0.2% or less, preferably 0.1% or less, and more preferably 0.05% or less silicon, which provides improved workability.

[0039] In one embodiment, the nickel-based alloy composition has at least 0.06%, preferably at least 0.07%, carbon, by weight, which provides improved grain boundary strength and improved creep and fatigue resistance.

[0040] In another aspect, the present invention provides a composition comprising, in mass %, 4.0 to 6.0% aluminum, 1.1 to 6.0% titanium, 0.0 to 4.0% niobium, 0.0 to 11.9% tantalum, 2.0 to 12.7% tungsten, 0.0 to 3.0% molybdenum, 0.0 to 22.0% cobalt, 6.0 to 16.7% chromium, 0.02 to 0.35% carbon, 0.001 to 0.2% boron, 0.0 to 0.01% zirconium, 0.0 to 3.0% rhenium, 0.0 to 3.0% ruthenium, 0.0 to 3.0% iridium, 0.0 to 3.0% vanadium, The alloy contains 0.0-0.5% niobium, 0.0-1.0% palladium, 0.0-1.0% platinum, 0.0-0.5% silicon, 0.0-0.1% yttrium, 0.0-0.1% lanthanum, 0.0-0.1% cerium, 0.0-0.1% sulfur, 0.0-0.003%, 0.0-0.25% manganese, 0.0-0.1% magnesium, 0.0-4.0% iron, 0.0-0.5% copper, and 0.3-2.0% hafnium, with the balance being nickel and unavoidable impurities. The mass percentages of niobium and tantalum contained in the alloy are respectively W. Nb , W Ta Then, a nickel-based alloy composition is provided that satisfies the following formula: 0.60≦0.3W Nb +0.15W Ta

[0041] In another alternative embodiment, the present invention provides a composition containing, in mass %, aluminum 4.0-6.0%, titanium 1.1-6.0%, niobium 0.0-4.0%, tantalum 0.0-11.9%, tungsten 2.0-12.7%, molybdenum 0.0-3.0%, cobalt 0.0-22.0%, chromium 6.0-16.7%, carbon 0.02-0.35%, boron 0.001-0.2%, zirconium 0.00-0.01%, rhenium 0.0-3.0%, ruthenium 0.0-3.0%, iridium 0.00-0.01%. The present invention provides a powder of a nickel-based alloy composition comprising 0.0 to 3.0% of zinc, 0.0 to 0.5% of vanadium, 0.0 to 1.0% of palladium, 0.0 to 1.0% of platinum, 0.0 to 0.5% of silicon, 0.0 to 0.1% of yttrium, 0.0 to 0.1% of lanthanum, 0.0 to 0.1% of cerium, 0.0 to 0.1% of sulfur, 0.0 to 0.003% of manganese, 0.0 to 0.25% of manganese, 0.0 to 0.1% of magnesium, 0.0 to 4.0% of iron, 0.0 to 0.5% of copper, 0.1 to 2.0% of hafnium, and the balance being nickel and unavoidable impurities.

[0042] In another aspect, the present invention provides a sintered body comprising, optionally in powder form, 4.6-5.0% aluminum, 1.1-1.35% titanium, 0.5-2.0% niobium, 2.5-4.5% tantalum, 6.2-7.6% tungsten, 0.5-1.8% molybdenum, 8.0-9.1% cobalt, 9.6-10.5% chromium, 0.06-0.35% carbon, 0.001-0.2% boron, 0.002-0.004% zirconium, 0.2-1.5% rhenium, 0.0-3.0% ruthenium, 0.0-3.0% indium, and 0.0-3.0% chromium. The alloy contains 0.0-0.5% vanadium, 0.0-1.0% palladium, 0.0-1.0% platinum, 0.0-0.5% silicon, 0.0-0.1% yttrium, 0.0-0.1% lanthanum, 0.0-0.1% cerium, 0.0-0.003% sulfur, 0.0-0.25% manganese, 0.0-0.1% magnesium, 0.0-4.0% iron, 0.0-0.5% copper, 0.8-1.2% hafnium, and the balance is nickel and unavoidable impurities. The mass percentages of niobium and tantalum contained in the alloy are W, respectively. Nb , W Ta Then, there is provided a nickel-based alloy composition, optionally satisfying the following formula: 0.60≦0.3W Nb +0.15W Ta

[0043] The term "comprising" is used herein to indicate that the composition is 100% and excludes the presence of additional components to make the percentage 100%. Unless otherwise specified, % is expressed as % by weight. [Brief explanation of the drawings]

[0044] [Figure 1] Figure 1 shows the calculated strain age figure of merit and hot tearing index for several commercially used superalloys (including those listed in Table 1). Figure 1 also shows the creep resistance, strain age cracking, and hot tearing limits. The target areas for this invention are indicated by hatching. [Figure 2] Figure 2 is a contour plot showing the effect of the gamma prime forming elements aluminum, niobium, and tantalum (following the 0.3WNb + 0.15WTa relationship) on the gamma prime volume fraction. The contour plot was obtained from a phase equilibrium calculation performed at 900°C. The graph shows different limits for the strain aging index and the hot tearing index. [Figure 3] Figure 3 shows a contour plot illustrating the effect of the gamma prime formers aluminum, niobium, and tantalum (following the relationship 0.3WNb + 0.15WTa) on the hot tearing index. The contour plot was determined by phase equilibrium calculations performed at 900°C. [Figure 4] Figure 4 is a contour plot showing the effect of gamma prime volume fraction and creep figure of merit on creep temperature capability. The contours are normalized to IN713C and show predicted positions for the alloys listed in Table 1. [Figure 5] Figure 5 is a contour plot showing the effect of elements molybdenum and tungsten on the creep figure of merit, showing the stability limits at various concentrations of chromium. [Figure 6]Figure 6 is a contour plot showing the effect of the elements molybdenum and tungsten on the alloy stability (in terms of Md number) for various levels of creep figure of merit, with the chromium content fixed at 6.0 wt%. [Figure 7] Figure 7 is a contour plot showing the effect of the elements molybdenum and tungsten on the alloy stability (in terms of Md number) for various levels of creep figure of merit, with the chromium content fixed at 8.0 wt%. [Figure 8] Figure 8 is a contour plot showing the effect of the elements molybdenum and tungsten on the alloy stability (in terms of Md number) for various levels of creep figure of merit, with the chromium content fixed at 10.0 wt%. [Figure 9] 9 is a contour plot showing the effect of the elements molybdenum and tungsten on the alloy stability (in terms of Md number) for various levels of creep figure of merit, with the chromium content fixed at 12.0 wt.%. [Figure 10] Figure 10 is a contour plot showing the effect of the elements molybdenum and tungsten on the alloy stability (in terms of Md number) for various levels of creep figure of merit, with the chromium content fixed at 14.0 wt%. [Figure 11] 11 is a contour plot showing the effect of the elements molybdenum and tungsten on the alloy stability (in terms of Md number) for various levels of creep figure of merit, with the chromium content fixed at 16.0 wt.%. [Figure 12] FIG. 12 is a contour plot showing the effect of tantalum and tungsten elements on alloy density. [Figure 13] FIG. 13 is a contour plot showing the effect of strain age cracking index and cobalt on the solidification range of the alloy. [Figure 14]Figure 14 compares the creep results of additively manufactured CM247 with the results of examples of alloys of the present invention (Examples 1 and 2 were not tested to failure, while CM247 was tested to failure). DETAILED DESCRIPTION OF THE INVENTION

[0045] Traditionally, nickel-base superalloys have been designed empirically. Thus, the chemical composition of a nickel-base superalloy has been identified through time-consuming and expensive experimental development involving small-scale processing of limited amounts of material and subsequent characterization of its behavior. The alloy composition found to exhibit the best, or most desirable, combination of properties is then adopted. The large number of alloying element families that can achieve this combination indicates that these alloys are not fully optimized and that improved alloys are likely to exist.

[0046] Chromium (Cr) and aluminum (Al) are commonly added to superalloys to provide oxidation / corrosion resistance, and cobalt (Co) is added to improve resistance to sulfidation. Molybdenum (Mo), tungsten (W), and cobalt are added for creep resistance because they inhibit thermally activated processes (e.g., dislocation climb) that determine the rate of creep deformation. Aluminum (Al), tantalum (Ta), niobium (Nb), and titanium (Ti) are added to improve static and cyclic strength because they promote the formation of the precipitation-hardening phase gamma prime (γ'). This precipitate phase is coherent with the face-centered cubic (FCC) matrix phase, called gamma (γ).

[0047] The model-based approach used to identify new grades of nickel-base superalloys is described herein as the "Alloy Design" (ABD) method. This approach utilizes a framework of computational materials models to estimate design-relevant properties over a very wide compositional range. In essence, this alloy design tool allows for the solution of a so-called inverse problem: identifying the optimum alloy composition that best satisfies specified design constraints.

[0048] The first step in the design process is to define the table of elements and the associated upper and lower compositional constraints. In this invention, the compositional constraints for each element's addition, called the "alloy design space," are considered. These compositional constraints are detailed in Table 2. Table 2 shows the alloy design space, in mass percent, explored using the "alloy design" method.

[0049] [Table 2]

[0050] The balance is nickel. The carbon, boron and zirconium levels were fixed at 0.06%, 0.015% and 0.06%, respectively.

[0051] The second step is based on thermodynamic calculations to calculate the phase diagrams and thermodynamic properties of a specific alloy composition. This is often called the CALculation of PHAse Diagrams (CALPHAD) method. These calculations are performed at the typical service temperature of the new alloy (900°C) to provide information about the phase equilibria (microstructure).

[0052] The third step involves identifying an alloy composition with the desired microstructure. For nickel-base superalloys requiring excellent resistance to creep deformation, creep rupture life improves gradually as the volume fraction of the precipitation-hardening phase γ' increases. The range of γ' volume fraction where creep rupture life is most beneficial is between 60 and 70%. Above 70% γ' volume fraction, a decrease in creep resistance is observed.

[0053] Furthermore, the γ / γ' lattice mismatch must be either positive or negative, whichever is smaller, to lose coherency. Therefore, the limit depends on the absolute value of the mismatch. The lattice mismatch δ is defined as the mismatch between the γ and γ' phases and is calculated by the following equation:

[0054]

number

[0055] where α γ and α γ´ are the lattice constants of the γ and γ′ phases.

[0056] Alloys based on inappropriate microstructures are also excluded by estimates of susceptibility to morphologically close packed (TCP) phases. Using CALPHAD modeling in this calculation, the formation of the deleterious TCP phases sigma (σ), P, and mu (μ) is predicted.

[0057] The model therefore identifies all compositions within the design space that have a desired calculated volume fraction of γ', where the γ' lattice mismatch is less than a predetermined absolute value and the total volume fraction of TCP phases is less than a predetermined magnitude.

[0058] In the fourth step, figures of merit are estimated for the identified alloy compositions remaining in the dataset. Examples of figures of merit include creep figure of merit (which indicates an alloy's creep resistance based on average composition only), strength figure of merit (which indicates an alloy's precipitation yield strength based on average composition only), solid solution figure of merit (which indicates an alloy's solid solution yield strength based on average composition only), density, and cost.

[0059] In the fifth stage, the calculated figure of merit is compared to constraints on the desired behavior, and these design constraints are considered boundary conditions for the problem. All compositions that do not satisfy the boundary conditions are rejected. At this stage, the size of the test dataset is significantly reduced.

[0060] The sixth and final step involves analyzing the remaining composition dataset. This analysis can be done in a variety of ways. One approach is to sort through the database for alloys with the highest Figure of Merit values, such as the lightest alloys, the most creep-resistant alloys, the most oxidation-resistant alloys, and the least expensive alloys. Alternatively, the database can be used to determine the relative performance tradeoffs offered by different combinations of properties.

[0061] Explain seven examples of merit figures.

[0062] The first figure of merit is the creep figure of merit. The most important observation is that the time-dependent deformation (i.e., creep) of nickel-base superalloys occurs via dislocation creep with initial activity limited to the gamma phase. Therefore, dislocation segments are rapidly pinned at the gamma / gamma phase interface due to the large fraction of gamma phase. The rate-determining step is the escape of the trapped dislocation configuration from the gamma / gamma interface. It is the local chemistry (in this case, the composition of the gamma phase) that causes the significant effect of alloy composition on creep properties.

[0063] The physics-based microstructural model assumes that the load is uniaxial. <001> Along the crystallographic direction, the creep strain ε · The set equation is:

[0064]

number

[0065] where ρ m is the mobile dislocation density, φ p is the volume fraction of the γ' phase, and ω is the width of the matrix channel. The terms σ and T are the applied stress and temperature, respectively. The terms b and k are the Burgers vector and Boltzmann constant, respectively. The term K CF is the constraint coefficient.

[0066]

number

[0067] term K CF describes the proximity of cubic particles in these alloys. Equation 3 describes the dislocation multiplication process, which requires an estimate of the multiplication parameter C and the initial dislocation density. The term D eff is the effective diffusivity that controls the ascending process at the particle / matrix interface.

[0068] In the above description, the composition dependence is expressed by two terms φ p and D eff Therefore, assuming the microstructure is constant (the microstructure is largely controlled by heat treatment), φ p is fixed, the dependence on chemical composition is eff For the purposes of the alloy design modeling described herein, it is recognized that it is not necessary to perform a full integration of Equations 2 and 3 for each prototype alloy composition. Instead, the first order figure of merit M creep is used. M creep is calculated using the following formula:

[0069]

number

[0070] where x i is the atomic fraction of solute i in the γ phase. D i ~ is the appropriate interdiffusion coefficient.

[0071] The second figure of merit is the strength figure of merit. In high-nickel-base superalloys, most of the strength comes from precipitate phases. Therefore, optimizing the alloy composition to maximize precipitation strength is an important design consideration. Based on hardening theory, the strength figure of merit M strength This index takes into account the maximum possible precipitation strength (determined as the point at which the transition of dislocation shear from weak to strong bonds occurs) and is approximated using the following equation:

[0072]

number

[0073] where M- is the Taylor coefficient, γ APB is the antiphase boundary (APB) energy, φ p is the volume fraction of the γ´ phase, and b is the Burgers vector.

[0074] From equation (5), it is clear that the defect energy in the gamma prime phase (e.g., the antiphase boundary APB energy) has a significant effect on the deformation behavior of nickel-based superalloys. Increasing the APB energy has been found to improve mechanical properties, including tensile strength and resistance to creep deformation. APB energy studies have been carried out for a number of Ni-Al-X systems using density functional theory. This work calculated the effect of ternary elements on the APB energy of the gamma prime phase, assuming a linear superposition of the effects of each ternary element addition when considering complex multicomponent systems. This resulted in the following equation:

[0075]

number

[0076] where x Cr , x Mo , x W , x Ta , x Nb and x Ti are the atomic percentage concentrations of chromium, molybdenum, tungsten, tantalum, niobium, and titanium in the gamma prime phase. The composition in the gamma prime phase is determined by phase equilibrium calculations.

[0077] The third figure of merit is density. Density ρ was calculated using a simple rule of mixtures and a correction factor, where ρ i is the density of a given element, and x i is the atomic fraction of the alloying element.

[0078]

number

[0079] The fourth figure of merit is cost. To estimate the cost of each alloy, we applied the simple rule of mixtures, where the cost of each alloy is the mass fraction of the alloying element x i 2. Current (2016) raw material costs of alloying elements i The value multiplied by was used.

[0080]

number

[0081] This estimate assumes that processing costs are the same for all alloys, i.e., product yields are not affected by composition.

[0082] The fifth figure of merit is based on the elimination of alloy candidates based on unsuitable microstructures made based on susceptibility to TCP phases. To do this, the d-orbital energy levels (referred to as Md) of the alloying elements are used to determine the total effective Md level according to the following formula:

[0083]

number

[0084] where x i represents the mole fraction of element i in the alloy. A higher value of Md indicates a higher possibility of TCP formation.

[0085] The sixth figure of merit is the strain-age cracking index. The performance of alloys manufactured by additive manufacturing is related to their chemical composition. This index was developed based on empirical observations relating alloy composition to the weldability of nickel-base superalloys in terms of susceptibility to strain-age cracking. In this relationship, because titanium is approximately twice as dense as aluminum, adding a factor of 0.5 to the titanium content converts it to an "aluminum equivalent." In effect, the additive manufacturing process for metal alloys is a continuous welding process. Previous observations relating weldability solely to the aluminum and titanium content have been adapted. A modification is included to account for the influence of tantalum and niobium, which behave similarly to aluminum and titanium during alloy aging. As with titanium, the additions of these elements are also factored to convert them to "aluminum equivalent." That is, the correction factors for niobium and tantalum (determined from their densities relative to aluminum) are 0.3 and 0.15, respectively. The following formula is applied to the strain aging index:

[0086]

number

[0087] where W Al , W Ti , W Nb and W Ta The strain aging index (SEA) values ​​are the mass percentages of aluminum, titanium, niobium, and tantalum, respectively, contained in the alloy. A lower strain aging index indicates a better response to the additive manufacturing process.

[0088] The seventh figure of merit is based on the solidification behavior of candidate alloys as predicted by the Scheil-Gulliver model. It ranks the hot tear susceptibility based on composition. In this approach, the temperature range at the end of solidification (90-99% solids) is considered to represent the region where the alloy becomes vulnerable to hot tearing. This is because at this stage, the liquid supply is likely to be limited by a bridged network of solid material. The temperature range at 40-90% solids is considered a safe region because at this stage, the liquid supply is significantly less restricted. The temperature range below 40% solids is considered unsuitable because the liquid is dominant.

[0089] According to the ranking system used by Clyne and Davis for casting alloys, the hot tearing index is defined as the ratio of the vulnerable temperature range to the safe temperature range, as follows:

number

[0090] The lower the value of this index, the lower the risk of hot tearing.

[0091] The ABD method described above was used to identify the alloy composition of the present invention. The design intent for this alloy is to develop a superalloy that has high creep resistance (achieved by increasing the γ' volume fraction) and improved processability by additive manufacturing (achieved by improving resistance to strain age cracking and hot tearing mechanisms) compared to other alloys with a higher γ' volume fraction. In addition to these attributes, good oxidation resistance is achieved by having sufficient levels of aluminum to form a protective aluminum-based oxide scale, optimizing other important material properties, including microstructural stability and alloy density.

[0092] The material properties (determined using the ABD method) of conventional compositions (listed in Table 1) are listed in Table 3. The predicted properties listed for these alloys were considered in the design of new alloys. Table 3 shows the calculated phase fractions and figures of merit generated by the "Alloy Design" software. The results are for the nickel-base superalloys listed in Table 1.

[0093] The design principles of the new alloy are explained below.

[0094] [Table 3]

[0095] The use of high γ' volume fraction superalloys with compositions originally designed for casting processes has several limitations. The alloys in Table 1 are limited by their lower creep performance than their cast counterparts and issues related to cracking defects during processing. Selected factors controlling creep resistance and cracking propensity are correlated, making optimizing this trade-off difficult. For example, an increase in strain-age cracking index propensity correlates with an increase in γ' volume fraction (Figure 2). Therefore, optimizing the balance between these two factors must be carefully managed to achieve the optimal balance between creep strength and cracking resistance. Figure 1 shows a narrow range of strain-age indexes that, combined with a sufficient AM processing window, allows for high creep resistance, which can significantly reduce or eliminate strain-age cracking. This is achieved by having a high γ' volume fraction (i.e., ignoring the creep merit index and grain boundary precipitation). Successful processing by AM is only achieved when the strain-age cracking index and hot-cracking index are both low. Hot tearing index is another cracking mechanism during AM that results from the solidification process when remelting the metal in the AM process.

[0096] To achieve high levels of creep resistance in the range of γ' volume fractions required for this invention, it is preferable that the strength of the γ matrix phase be sufficiently high, as determined by the creep figure of merit (Figure 4). Additionally, the inventors have found that to achieve high creep resistance, particularly the formation of titanium carbide with high reaction rate and high thermodynamic stability, it is desirable to control the grain boundary strength, which provides resistance to intergranular cracking and sliding during creep.

[0097] FIG. 2 shows the relationship between the amounts of aluminum, niobium, and tantalum added, which are predominantly added to form the γ' phase and control the γ' volume fraction.

[0098] Elements that form the γ' phase can increase the strain-age figure of merit and therefore reduce the alloy's processability by AM (Equation 10). Therefore, it is necessary to optimize the combination of these elements to provide the desired balance between limiting the potential for strain-age cracking during AM processing and the γ' volume fraction (which provides strength in terms of creep resistance and tensile strength).

[0099] To achieve a preferred strain age cracking index, the aluminum, titanium, niobium and tantalum contents must satisfy the following constraints: f(SAC)=W Al +0.5W Ti +0.3W Nb +0.15W Ta

[0100] where f(SAC) is a value less than or equal to 7.0, and W Al , W Ti , W Nb and W Ta The values ​​of f(SAC) above 7.0 are not preferred because they limit alloy processing from the perspective of strain-age cracking. To make processing by AM easier, it is desirable to lower the strain-age figure of merit. That is, W Al +0.5W Ti +0.3W Nb +0.15W Ta ≦6.5 is preferred.

[0101] The intended application temperature of this new alloy is up to 1000°C in highly oxidizing and corrosive environments. Example applications include high-temperature sections in the exhaust systems of gas turbine engines or internal combustion engines.

[0102] To achieve desirable oxidation performance, the alloys of the present invention desirably need to form a protective aluminum-based oxide scale (Al2O3). Such alloys, in contrast to those based on Cr2O3, are stable above 1000°C. While alloys such as IN738 and IN792 have a relatively high γ' volume fraction and excellent creep resistance, their relatively low aluminum content (3.4% and 3.2%, by weight, respectively) prevents them from forming a protective aluminum-based oxide scale, resulting in the formation of a less protective chromium-based oxide scale instead. While aluminum-based oxide scales offer excellent adhesion and thermal stability, chromium-based protective oxide scales can undergo chromium volatilization near 1000°C, resulting in a less protective oxide. To produce a protective aluminum-based oxide scale, an aluminum content of at least 4.0%, by weight, is required, preferably 4.3% or more, and more preferably 4.5% or more. This further improves alumina scale formation and oxidation resistance.

[0103] As will be discussed below in order to improve the creep resistance of the alloy, titanium can be used in amounts of 1.1% by weight or greater to increase the gamma-prime strength of the alloy and stabilize carbides, pinning grain boundaries at high temperatures to improve creep resistance. Based on the minimum (4.0% by weight) and preferred minimum (4.5% by weight) aluminum content, the maximum amount of titanium is 6.0% and preferably 5.0% by weight to achieve f(SAC) < 7.0 and f(SAC) < 6.5, respectively. Based on the titanium content (at least 1.1% by weight), the maximum aluminum content is limited to 6.45% by weight, and more preferably 5.95% by weight, to achieve f(SAC) < 7.0 and f(SAC) < 6.5, respectively. However, as will be apparent below, aluminum is limited to 6.0% by weight to improve hot tearing performance. In a preferred embodiment, the alloy contains 1.2% by weight or greater titanium, and in a most preferred embodiment, the alloy contains 1.3% by weight or greater titanium to further enhance creep strength. In embodiments optimizing strain age cracking resistance over creep strength, titanium is limited to not more than 3.0 wt.%, preferably titanium is limited to not more than 2.0 wt.%, more preferably not more than 1.5 wt.%, even more preferably not more than 1.4 wt.%, most preferably not more than 1.3 wt.% titanium (or not more than 1.35 wt.% titanium), and even more preferably not more than 1.2 wt.% titanium. In one embodiment, the alloy contains 1.1-1.25 wt.% titanium to achieve a balance between creep strength and strain age cracking resistance.

[0104] Alloying additions of niobium and titanium are known to reduce oxidation performance. Niobium forms grain boundary carbides, which are particularly detrimental to oxidation-assisted cracking mechanisms, which can accumulate damage along grain boundaries under low-cycle fatigue, creep-fatigue, or high-temperature creep conditions. Titanium promotes oxide scale growth and forms as rutile above and below protective oxide scales based on Al2O3 and Cr2O3, which can also adversely affect mechanical performance and is therefore undesirable. However, because niobium additions are beneficial for improving hot-cracking resistance (discussed later with reference to Figure 3), their use is optional, but should be limited to 4.0 wt%, more preferably 3.0 wt%, and even more preferably 2.0 wt%, to achieve the desired balance of hot-cracking resistance while achieving good oxidation resistance. Titanium has a lower Pilling-Bedworth ratio, making it less susceptible to oxidation than niobium. The Pilling-Bedworth ratio describes the volume expansion of a metal when oxidized. This volume expansion creates stresses around the oxide, potentially leading to cracking. The Pilling-Bedworth ratios for niobium and titanium are 2.69 and 1.73, respectively. Alloys IN792 and In738 have relatively high titanium contents, yet exhibit acceptable levels of oxidation. While the alloys of the present invention have high creep resistance due to their high titanium content, and correspondingly reduced oxidation resistance, this balance of properties can be useful in some situations, and oxidation resistance can be mitigated by other means, such as coating the article or controlling the environment in which the article operates. However, when better oxidation resistance is important, titanium is preferably 4.2% by weight or less (IN792), more preferably 3.4% by weight or less (IN738), and most preferably 2.5% by weight or less. As discussed elsewhere, aluminum and chromium additions can be increased to achieve even better levels of oxidation resistance, and in some embodiments, this can compensate for high levels of titanium, which may otherwise reduce oxidation resistance.Increasing the aluminum and chromium levels beyond the minimum allowable values ​​described elsewhere increases the activity of aluminum in the alloy, thereby improving oxidation resistance (G.S. Giggins et al., Oxidation of Ni-Cr-Al Alloys Between 1000°C and 1200°C, Journal of the Electrochemical Society, 118(1971),1782), but also promotes more rapid growth of alumina oxide scale. Preferably, at least 4.3% aluminum and / or at least 8.0% chromium, by weight, are added. In one embodiment, to improve oxidation resistance, regardless of the aluminum content, the chromium is at least 8.5%, or 9.0%, or 9.5%, or 9.75%, by weight. More preferably, the aluminum content is at least 4.5% by weight (or at least 4.6% aluminum, by weight) and / or the chromium content is at least 10.0% by weight.

[0105] The addition of chromium promotes the formation of a protective alumina oxide scale. Chromium, in particular, is desirable for improving resistance to high-temperature corrosion. Alloys such as IN738 and IN792 contain relatively high levels of chromium (16.0% and 12.7%, by weight, respectively). This is primarily for their resistance to high-temperature corrosion, but because they do not form protective aluminum-based oxides, they have slow oxidation rates at very high temperatures, thereby limiting their maximum operating temperatures. These alloys also have lower creep resistance compared to IN713C (Figure 4), limiting their upper operating temperature limits. The alloys of the present invention must contain 6.0% or more chromium, by weight. Chromium levels of 6.0% or more, by weight, are desirable to achieve good high-temperature corrosion and creep resistance. As discussed below in relation to creep, chromium is desirably added in combination with controlled levels of boron to achieve high creep resistance through the formation of M5B3-type chromium boride precipitates, which are highly stable at high temperatures and promote grain boundary strength (P. Kontis et al., Atomic-scale grain boundary engineering to overcome hot-cracking in additively manufactured superalloys, Acta Materialia, 177 (2019), 209-221). More preferably, the chromium content is 8.0% by weight or greater to provide high-temperature corrosion resistance equivalent to that of CM247LC. Even more preferably, chromium is present in an amount of 9.6% or greater, or 10.0% or greater, which further enhances corrosion resistance compared to alloy CM247LC. Even better corrosion resistance is achieved by increasing the chromium content in the alloy to a minimum of 10.1% by weight, e.g., 10.1% to 10.5% by weight.

[0106] Molybdenum is known to significantly reduce the hot corrosion resistance of nickel-based superalloys. It also has the advantage of imparting high strength to the gamma matrix phase, which is beneficial for improving tensile strength and creep resistance. While molybdenum is an optional addition, a minimum of 0.1% or 0.2% by weight provides alloys with improved tensile strength and creep resistance. These benefits are achieved by using an element with a lower density than other elements with similar technical effects, particularly tungsten and rhenium. A minimum level of molybdenum, or at least 0.5% by weight, is desirable for improving strength and creep resistance. To achieve good corrosion resistance, molybdenum is limited to 3.0% by weight or less. Preferably, molybdenum is limited to 2.0% by weight or less. Since alloys IN738 and IN792 are known for their excellent corrosion resistance, molybdenum is more preferably limited to 1.8% by weight or less. Even better corrosion performance is achieved in embodiments where the alloy has 1.5% or less molybdenum, or 1.4% or less molybdenum, or even 1.3% or less molybdenum.

[0107] Based on the minimum aluminum content (4.0 wt%) and the desirability of f(SAC)<7, and the requirement that the alloy contain a minimum of 1.1 wt% titanium, 0.3W Nb +0.15W Ta The sum of the elements tantalum and niobium, which obeys the relationship, should be limited to 2.45 or less. Therefore, the upper limits of niobium and tantalum should be 8.1% and 16.3%, by weight, respectively. However, to ensure sufficient microstructural stability (tantalum) and oxidation resistance (niobium), the amounts of niobium and tantalum in the alloy should be further limited. Preferably, 0.3W should be used to improve the balance between oxidation resistance (aluminum 4.5% by weight or more) and strain age cracking resistance (f(SAC)<6.5). Nb +0.15W Tais limited to 1.95 or less. Therefore, the upper limits of niobium and tantalum are more preferably 4.8% by mass and 9.7% by mass, respectively. When aluminum is 5.0% by mass and f(SAC)<6.5, the balance between resistance to strain age cracking and oxidation resistance is most favorable. That is, 0.3W Nb +0.15W Ta It is most preferable that the niobium and tantalum contents are limited to 3.2% and 6.3% by weight, respectively.

[0108] In Figure 2, dotted lines are shown indicating various limits of strain age cracking. It can be seen that to produce alloys with a strain ageing index of 7 or less, it is preferable to limit the gamma prime volume fraction to 0.63 at the equilibrium temperature of 900°C. Preferably, the gamma prime volume fraction is less than the strain ageing index W. Al +0.5W Ti +0.3W Nb +0.15W Ta Limited to 0.56, with a more preferred value of ≦6.5.

[0109] The desired minimum gamma prime volume fraction requirement is 0.42, which will be explained later in relation to achieving the required creep resistance using Figures 4 and 5. To achieve the desired gamma prime volume fraction, the aluminum, titanium, niobium, and tantalum contents must satisfy the following constraints: f(γ´)=W Al +0.5W Ti +0.3W Nb +0.15W Ta

[0110] Here, f(γ') is a value in the range of 5.6 to 7.0, producing alloys with desirable γ' fractions of 0.42 to 0.63. When f(γ') is a value in the range of 5.6 to 6.5, alloys with γ' fractions of 0.42 to 0.56 are produced, resulting in alloys with an improved combination of high creep strength and high AM processability. As discussed below with respect to improving the creep resistance of the alloy, the γ' fraction is preferably 0.43 or greater, more preferably 0.45 or greater, and most preferably 0.50 or greater. This results in preferred values ​​of f(γ') of 5.7 or greater, 5.8 or greater, and 6.0 or greater, respectively.

[0111] The elements platinum and palladium behave similarly to tantalum, titanium, and niobium; that is, they are gamma prime formers that increase antiphase boundary energy. These elements can be selectively added to alloys in place of tantalum, titanium, and niobium. Benefits of this can include improved high-temperature corrosion resistance. The "aluminum equivalents" of platinum and palladium require correction factors of 0.125 and 0.225 (determined from their densities relative to aluminum), respectively. However, due to the high cost of adding these elements, the amount of these elements added may be limited. Therefore, these elements can be present at a maximum of 1.0% by weight each, preferably limited to 0.5% by weight or less, and most preferably limited to 0.1% by weight or less. This range provides an optimal balance between cost and improved corrosion resistance. For successful additive manufacturing, the following formula is preferably satisfied: W Al +0.5W Ti +0.3W Nb +0.15W Ta +0.125W Pt +0.225W Pd ≦7.0 Preferably, the following formula is satisfied: W Al +0.5W Ti +0.3W Nb +0.15W Ta +0.125W Pt+0.225W Pd ≦6.5

[0112] where W Pt and W Pd indicates the mass percentages of platinum and palladium contained in the alloy, respectively.

[0113] The tendency of an alloy to form hot tears is determined in terms of the hot tearing index (Equation 11). This hot tearing mechanism is caused by elements that segregate primarily to the liquid phase during solidification. In the design region investigated (Table 2), niobium and tantalum have the strongest influence on hot tearing, since they are the elements that segregate most strongly to the liquid phase.

[0114] Figure 3 shows the hot-tearing index as a function of aluminum, niobium, and tantalum elements. These elements promote strain-age cracking (as explained in connection with Figure 1, a balance between strain-age cracking and hot-tearing is necessary for optimal AM processability). Niobium and tantalum strongly influence the hot-tearing index. The alloys listed in Table I are highly prone to hot-tearing during AM, with alloy IN738 exhibiting the lowest hot-tearing resistance with an index of 1.8. For example, careful control of zirconium and silicon levels in IN738 has demonstrated that hot-tearing can be nearly eliminated, and therefore is considered the upper limit of the composition for resistance to hot-tearing (M. Vilanova et al., Influence of Minor Alloying Element Additions on the Crack Susceptibility of a Nickel-Based Superalloy Manufactured by LPBF, Materials. 14, (2021), 5702). Alloys that process very well in AM and do not exhibit hot tearing, such as Alloy 718 and Alloy 625, have a Hot Tearing Index of 1.0 or less (Figure 1). For alloys with significantly better resistance to hot tearing, an index of 1.8 or less (similar to or less than IN738) is useful, and Figure 3 indicates that to achieve the desired Hot Tearing Index, the niobium and tantalum contents must meet the following constraints: f(HCI)=0.3W Nb +0.15W Ta

[0115] Here, f(HCI) is a numerical value, and a value of 0.6 or greater achieves a hot tearing index of 1.8 or less. A line representing a hot tearing index of 1.8 is superimposed on Figure 2. It can be seen that to achieve a hot tearing index of 1.8 or less in combination with a strain age cracking index of 7.0 or less, aluminum must be limited to 6.0% by weight or less. More preferably, a hot tearing index of 1.8 or less in combination with a strain age cracking index of 6.5 or less is desirable, so aluminum is preferably limited to 5.6% by weight. In one embodiment, aluminum is limited to 5.5% by weight or less, or even 5.3% by weight or less, to further enhance strain age cracking resistance. In one embodiment, the alloy contains 5.2% by weight or less aluminum, preferably 5.1% by weight or less. Such alloys are particularly resistant to hot cracking. In one embodiment, aluminum is limited to 5.0% by weight or less, or 4.95% by weight or less. A particularly good aluminum content is 4.85% to 4.85% by weight, especially when combined with a chromium content of 10.0% or more, or 10.1% to 10.5% by weight, which provides good physical properties and good oxidation resistance (see Example 1). In one embodiment, the intentional addition of niobium and / or tantalum increases hot-tearing resistance. Suitable preferred minimum amounts of niobium are 0.05% or more, 0.5% or more, or even 1.0% or more, by weight. Suitable preferred minimum amounts of tantalum are 1.1% or more, 2.0% or more, or even 2.5% or more, by weight. In one embodiment, an f(HCl) of the alloy is 0.625 or more, or even 0.65 or more, which advantageously improves hot-tearing resistance.

[0116] The addition of cobalt has the effect of lowering the γ' solvus temperature. Lowering the γ' solvus temperature is desirable because it lowers the temperature at which γ' precipitation occurs. This is advantageous for slowing the rate at which strain-age hardening occurs, since the rate at which strain-age hardening occurs is dependent on γ' precipitation. Lowering the γ' solvus also improves the ability to perform solution treatments. The ability to perform solution treatments is necessary to homogenize the distribution of elemental species resulting from the AM process and to modify certain microstructural features, such as increasing grain size, and to dissolve coarse γ' precipitates that do not provide significant strengthening. Rapid cooling from the solution treatment temperature can achieve a fine dispersion of γ' grains, which helps improve mechanical properties. Cobalt can be added as an optional element, optionally substituting for nickel. In one embodiment, to take advantage of these effects, the alloy may contain, by weight percent, 5.5% or more cobalt, preferably 6.0% or more cobalt. It is desirable to use a minimum level of cobalt of 7.0% by weight or greater, or 8.0% by weight or greater, and all of the example alloys described below have at least these levels of cobalt. A more preferred minimum level of cobalt is 9.0% by weight, with an even more preferred limit being 10.0% by weight or greater. In one embodiment, cobalt is present at 8.0-9.0% by weight (see Example 1), resulting in an excellent balance between gamma and the freezing range.

[0117] However, increasing the cobalt content increases the shale solidification temperature range of the alloy (Figure 13). Because an increased freezing range is associated with an increased time to solidification and may pose a risk of solidification cracking if the alloy is in a semi-solid state, limiting the freezing range is desirable. A target freezing range of 300°C or less is desirable, meaning up to 22.0% cobalt, by weight, is permitted. To match the freezing range of IN792, a cobalt content of 15.0% or less, by weight, is desirable, and it is even more desirable to limit the cobalt content to 10.0% or less, by weight. In one embodiment, to further reduce the freezing range, cobalt is limited to 9.5%, 9.1%, or 9.0% or less, by weight.

[0118] The relationship between creep resistance and gamma prime volume fraction versus creep figure of merit (in terms of temperature capability at 137 MPa, with contours normalized to IN713) is shown in Figure 4. Increasing both parameters increases creep resistance, and the sensitivity to each parameter is determined. The locations of the alloys listed in Table 3 are shown in Figure 4. The goal of this invention is to have creep performance equivalent to IN713C, and more preferably, a 25°C improvement.

[0119] For the alloys of the present invention, it is desirable to have a creep figure of merit higher than that of alloy IN713C. Thus, for the alloys of the present invention, a creep figure of merit of 6.0 x 10 -15 m -2 s is desirable. The elemental additions required to achieve this level of creep figure of merit are reviewed in the following section with reference to Figure 5. The maximum achievable creep figure of merit is determined by the need for the alloy to contain a minimum of 6.0 wt.% chromium for corrosion resistance while maintaining a stable microstructure essentially free of TCP phases (see Figure 5). To obtain creep resistance equivalent to IN713C, a γ' volume fraction of 0.42 is desirable. More preferably, a minimum 25°C improvement in creep resistance over IN713C is desirable. Therefore, a creep figure of merit of 6.0 × 10 is particularly desirable. -15 m -2In the case of s, the γ' volume fraction is preferably 0.50, which corresponds to a value of f(γ') of 6.0 or more.

[0120] Slow-diffusing elements that partition into the gamma matrix phase have the strongest effect on the creep figure of merit. This creep figure of merit is calculated based on the composition of the gamma phase at the equilibrium temperature of 900°C. Tungsten is the slowest-diffusing element in the alloy design region listed in Table 2, followed by molybdenum. The effect of tungsten and molybdenum elements on creep resistance is shown in Figure 5. From Figure 5, it can be determined that the change in creep figure of merit is related to the sum of molybdenum and tungsten elements based on the following equation: f(CMI)=W W +0.65W Mo

[0121] where f(CMI) is a numerical value, and Ww and W Mo indicates the mass percent of tungsten and molybdenum in the alloy, respectively. The desired creep figure of merit is 6.0×10 -15 m -2 To achieve this, an f(CMI) value of 4.0 or greater is desirable. Based on the upper limit of molybdenum (3.0% by mass), the tungsten content must be a minimum of 2.0% by mass. More preferably, since molybdenum is limited to 2.0% by mass, the tungsten content is preferably 2.7% by mass or greater. Most preferably, since molybdenum is limited to 1.8% by mass, the tungsten content should be a minimum of 2.8% by mass or greater. A more desirable f(CMI) level is 6.0 or greater, preferably 8.0 or greater.

[0122] For an even better combination of creep resistance and strain age cracking resistance, a 25°C improvement in temperature capability over IN713C is desired, combined with a strain age cracking index of 6.5 or less. This limits the maximum gamma prime volume fraction to 0.56, thus 6.90 × 10 -15 m -2 A creep figure of merit of 6.90×10 s or more is required. -15 m-2 To achieve a creep figure of merit of s or greater, a value of f(CMI) of 6.4 or greater is required. Based on the upper limit of molybdenum (3% by weight), a minimum tungsten content of 4.7% by weight is required. More preferably, molybdenum is limited to 2.0% by weight, i.e., a tungsten content of 5.1% by weight or greater. Most preferably, molybdenum is limited to 1.8% by weight, i.e., a minimum tungsten content of 5.2% by weight or greater. In an embodiment further optimized for improved creep resistance, tungsten is present in an amount of 6.2% by weight or greater.

[0123] The elements rhenium, ruthenium, and iridium behave similarly to tungsten. That is, they are gamma-forming elements that improve the creep figure of merit. These elements can be selectively added to alloys. Addition of these elements significantly improves the creep response of the alloy compared to tungsten (due to its much slower diffusivity), but significantly increases the cost due to the high cost of the elements. Due to the cost of the elements, the addition of rhenium, ruthenium, and iridium is preferably limited to 3.0% by weight or less, even more preferably 2.0% by weight or less, and most preferably 1.5% by weight or less. The addition of rhenium (e.g., as a replacement for tungsten) is particularly desirable, improving the balance between creep resistance and oxidation-corrosion resistance of the alloy while maintaining alloy stability. For this reason, it is preferable to keep the rhenium content high, e.g., 2.9% or less, or 2.5% or less, when cost reduction is a more important factor in the alloy design than creep or oxidation-corrosion resistance. 6-10, it can be seen that the use of rhenium instead of tungsten achieves higher levels of chromium, improves oxidation resistance at a given creep figure of merit, and improves creep while maintaining a desirable level of microstructural stability. Rhenium can be substituted for W at a ratio of 0.3% Re to 1% In. In one embodiment of the present invention, to achieve the desired combination of creep strength, oxidation / corrosion resistance, and microstructural stability, the amount of rhenium added is 0.1% by weight or more, preferably 0.2% by weight or more, preferably 0.3% by weight or more, more preferably 0.5% by weight or more, and most preferably 0.8% by weight or more.

[0124] There is a trade-off between creep resistance (in terms of creep figure of merit), alloy stability (in terms of Md number), and the corrosion resistance of an alloy (in terms of chromium content). The limits of alloy stability at various levels of chromium content, as determined by the f(stability) equation (discussed below with reference to Figures 6-10), are shown in Figure 5. It can be seen that as chromium increases for a given microstructural stability, the creep figure of merit decreases. Therefore, lowering the level of chromium appears to be beneficial for increasing microstructural stability and creep figure of merit.

[0125] Improved oxidation resistance, especially corrosion resistance, is attributed to the addition of chromium. However, the addition of molybdenum and tungsten for creep resistance, along with the addition of chromium for oxidation and corrosion resistance, increases the alloy's propensity to form unwanted TCP phases. Figures 6–10 show the effect of tungsten and molybdenum additions on phase stability for alloys containing various levels of chromium. The higher the stability number, the more prone the alloy is to TCP phase formation. Because TCP phases cause degradation of material properties over time, it is beneficial to limit or halt the precipitation of TCP phase formation. A complex tradeoff must be managed between mechanical performance, oxidation / corrosion resistance, and microstructural stability.

[0126] To ensure microstructural stability and avoid TCP formation, it is desirable to have a target stability number (Md) of 0.93 or less (determined at an equilibrium temperature of 900°C) (see prior art alloys in Table 3). A target stability number of 0.92 or less is even more desirable to ensure better microstructural stability and avoid TCP formation. From data such as Figures 6-10, it was determined that for alloys with a γ' volume fraction of 42-63%, assuming a minimum tungsten content of 2.0% by weight, chromium need only be present at 16.7% by weight or less to achieve the desired microstructural stability (Md 0.93 or less). At a chromium level of 6.0% by weight, a maximum limit of 12.7% by weight of tungsten can be included in the alloy to meet the stability target of 0.93. The preferred chromium content is 8.0% by weight, and more preferably 10.0% by weight, resulting in tungsten being limited to 10.7% by weight and 8.7% by weight, respectively. In one embodiment, tungsten is limited to 9.5% by weight or less. In other embodiments, tungsten is limited to 8.5% by weight or less, or 8.0% by weight or less, to further reduce the density and increase the microstructural stability of the alloy. In one embodiment, where density reduction and microstructural stability are paramount, tungsten is limited to 7.6% by weight or less (or 7.5% by weight or less).

[0127] The best balance of creep and corrosion resistance (while maintaining alloy stability) is achieved when tungsten (based on f(CMI)) is equal to 4.0%, by weight. Therefore, it is preferred to limit the maximum chromium content of the alloy to 14.7%, by weight. This allows for a 4.0%, by weight, tungsten content and a stability number Md of 0.93 or less. It is preferred to limit the stability number to 0.92. Therefore, it is preferred to limit the chromium content to 13.8%, by weight. This limits the stability number to 0.92 and improves microstructural stability.

[0128] In combination with a high level of mechanical strength (in terms of creep resistance), it is necessary to limit the density of the alloy to 8.9 g / cm 3A target density of 0.015 is imposed, which is typical of the upper density limit for commercially used nickel-base superalloys. According to the elements within the alloy design domain listed in Table 2, the elements tungsten and tantalum have significantly higher densities than nickel and have the strongest influence on increasing density. Figure 12 shows the effect of tantalum and tungsten on alloy density. From Figure 12, it can be seen that the amounts of tungsten and tantalum added should follow the formula: f(density)=W W +W Ta

[0129] Here, f (density) is 8.9 g / cm 3 To achieve an alloy with a density of 13.9 or less, the tantalum concentration must be limited to 11.9 mass% or less, taking into account the required minimum concentration of tungsten (2.0 mass%). Preferably, the density is 8.8 g / cm 3 To achieve this, the f(density) value must be 11.8 or less, and therefore tantalum must be 9.8% or less by weight. Even more preferably, tungsten must be 4.7% or more by weight, and therefore tantalum must be limited to 9.2% and 7.1% by weight, respectively. This achieves f(density) values ​​of 13.9 and 11.8, respectively. Lower levels of tantalum (e.g., 7.1% or less by weight, which is a more desirable maximum level of tantalum and includes all of the following alloy examples) allow for selectively increasing the tungsten level while still limiting the alloy's density. Density reduction is achieved by limiting tantalum to 5.5% or less by weight, or 5.0% or less by weight. In one embodiment, for applications where low density is important, tantalum is permitted to be 4.5% or less by weight to further reduce density. Most preferably, tantalum is limited to 4.0% or less by weight to further reduce the alloy's density.

[0130] The addition of carbon, boron, and zirconium provides strength to the grain boundaries, which is particularly beneficial for the creep and fatigue properties of the alloy. The carbon concentration should be in the range of 0.02% to 0.35% by weight (e.g., 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.2, 0.3, or 0.35% by weight, or any range or value therein). Lower levels of carbon are preferred to reduce cracking during the additive manufacturing process. Therefore, carbon is preferably present in an amount of 0.2% by weight or less, or 0.15% by weight or less, and more preferably 0.1% by weight or less. In one embodiment, to strengthen the grain boundaries, the carbon level is 0.05% by weight or more, such as 0.06% by weight or more (or 0.07% by weight or more). This is a much higher carbon level than previously used. For example, in alloys intended for use as single crystals (without grain boundaries requiring strengthening), the presence of carbon is detrimental because it provides nucleation sites (impairing the ability of the alloy to be formed into a single crystal product) and / or reduces oxidation performance through the formation of large crystalline carbides. Because boron can separate into the liquid phase during solidification and cause liquation cracking during the AM process, the boron concentration should be in the range of 0.001-0.2 wt.%, preferably 0.03 wt.% or less, and more preferably 0.02 wt.% or less. In one embodiment, zirconium is present at 0.001 wt.% or more to enhance grain boundary strength. In one embodiment, zirconium is present at at least 0.002 wt.%, e.g., 0.002-0.004 wt.%, to achieve a balance between increased grain boundary strength.

[0131] For alloys developed for AM, having strong grain boundaries is particularly advantageous due to smaller grain sizes than conventional casting alloys. Dispersion of MC carbides is effective in suppressing grain boundary sliding at temperatures above 800°C. Titanium and hafnium are particularly attractive elements for strengthening grain boundaries in AM superalloys because they are strong carbide formers. Titanium is particularly beneficial as a carbide because of its high reactivity and ease of formation during the AM process. Titanium forms highly stable MC carbides, so titanium is added to alloys at levels of 1.1% by weight or more. In addition to improving creep resistance, titanium carbide particles have been shown to act as nucleation agents during AM. This nucleation effect promotes more heterogeneous nucleation, further reducing susceptibility to hot tearing (H. Quanquan, Additive manufacturing of high-strength crack-free Ni-based Hastelloy X superalloy, 30 (2019), 1009). The improved creep resistance is experimentally demonstrated in Figure 14 below.

[0132] The inclusion of hafnium in titanium carbide to form a (Ti,Hf)C-type MC carbide is particularly advantageous because hafnium further stabilizes the carbide. While adding up to 2.0% by weight of hafnium (Hf) is desirable, because hafnium is an expensive element and its high reactivity can make alloy powder manufacturing more difficult, it is preferably limited to 1.5% by weight, with an upper limit of 1.2% by weight being more preferred, and an upper limit of 1.1% by weight being even more preferred. Furthermore, hafnium helps improve oxidation resistance by increasing the adhesion of the protective Al2O3 oxide layer. Therefore, a minimum hafnium content of 0.1% by weight or more is desirable. From the perspective of improving creep strength and oxidation resistance at the expense of increased cost, the minimum hafnium content is 0.2% by weight, or 0.25% by weight or more, or 0.3% by weight or more, and even more preferably 0.5% by weight. The best creep strength and oxidation resistance are achieved with a hafnium content of 0.6 wt.% or greater, which is most preferred, but in one embodiment optimized for improved creep strength and oxidation resistance, a minimum of 0.8 wt.% hafnium is present, resulting in an expensive but high performance alloy. In one embodiment, hafnium is present at 0.8-1.2 wt.% to achieve high mechanical properties and oxidation resistance.

[0133] In the case of boron additions, increasing the chromium content is advantageous, as high levels of chromium promote the formation of Cr5B3-type borides, which are highly stable at high temperatures and have the effect of strengthening grain boundaries and improving creep resistance. Therefore, to achieve the best balance between printability and creep resistance, the alloy preferably contains at least 8.0% (or 8.5% by weight) chromium, and more preferably at least 9.0% by weight chromium. A boron concentration of 0.005% by weight or greater is preferred because it contributes to improved grain boundary strength and ductility. These effects are even more pronounced when boron is present at a concentration of 0.006% by weight or greater, and this is preferred. When boron is present at levels of 0.010% by weight or greater, these effects are even more pronounced, and this level of boron is preferred. To achieve the desired balance between AM processability and creep resistance, the boron content is preferably between 0.008% and 0.018% by weight, and more preferably between 0.008% and 0.015% by weight. In one embodiment, boron is present at a level of less than or equal to 0.012% by weight.

[0134] The zirconium concentration should be limited to 0.01% by weight or less, preferably 0.005% by weight or less, more preferably 0.002% by weight or less, and most preferably 0.0015% by weight or less. These limitations on the zirconium content reduce the level of hot cracking (M. Vilanova et al., Influence of Minor Alloying Element Additions on the Crack Susceptibility of a Nickel-Based Superalloy Manufactured by LPBF, Materials. 14, (2021), 5702).

[0135] When the alloy is manufactured, it is beneficial for it to be substantially free of unavoidable impurities. These impurities may include elemental sulfur (S), manganese (Mn), and copper (Cu). Elemental sulfur is preferably maintained at 0.003% by weight (30 ppm by weight) or less. Presence of more than 0.003% sulfur embrittles the alloy and causes sulfur segregation at the alloy / oxide interface formed during oxidation. Therefore, sulfur levels are preferably 0.001% by weight or less. Manganese is an unavoidable impurity and is limited to 0.25% by weight, preferably 0.1% by weight or less. Copper (Cu) is an unavoidable impurity and is preferably limited to 0.5% by weight. Vanadium (V) is an unavoidable impurity and adversely affects the oxidation behavior of the alloy, so is preferably limited to 0.5% by weight, preferably 0.3% by weight, and most preferably 0.1% by weight. This segregation can increase spalling of the protective oxide scale. If the concentration of these unavoidable impurities exceeds a certain level, problems surrounding product yields will arise and deterioration of the material properties of the alloy will be expected.

[0136] Iron behaves similarly to nickel and can be added as a low-cost alternative to nickel. Furthermore, allowing the addition of iron improves the alloy's ability to be produced from recycled materials. Therefore, iron is preferably present in an amount of at least 0.1% by weight. However, to significantly reduce costs, iron can be added up to 4.0% by weight. Preferably, the iron addition is no more than 2.0% by weight to reduce the tendency to form undesirable Laves phases that reduce the alloy's mechanical properties. Most preferably, the iron addition is limited to 1.0% by weight. This produces an alloy with good recycling capabilities without compromising material performance.

[0137] So-called "reactive elements" (yttrium (Y), lanthanum (La), and cerium (Ce)) are added at levels up to 0.1 wt. %. This is beneficial for improving the adhesion of protective oxide layers such as Al2O3. These reactive elements can "scavenge" harmful elements such as sulfur, which segregates at the alloy-oxide interface, weakening the bond between the oxide and the substrate and leading to oxide spalling. Magnesium (Mg) also exhibits "scavenging" behavior for harmful elements and can have a beneficial effect on mechanical properties, so it can be added at levels up to 0.1 wt. Silicon (Si) can be beneficial at levels up to 0.5 wt. Silicon additions to nickel-base superalloys at levels up to 0.5 wt. have been shown to be beneficial for oxidation properties. In particular, silicon segregates at the alloy / oxide interface, improving the bonding strength of the oxide to the substrate. This reduces oxide spalling, resulting in improved oxidation resistance. On the other hand, silicon can reduce the AM processability of the element, so it is advantageous to limit its content to 0.2% by weight or less, more preferably 0.1% by weight or less, and even more preferably 0.05% by weight or less (M. Vilanova et al., Influence of Minor Alloying Element Additions on the Crack Susceptibility of a Nickel-Based Superalloy Manufactured by LPBF, Materials. 14, (2021), 5702).

[0138] The alloys of the present invention are designed for superior additive manufacturing (AM) performance. Therefore, they are suitable for processing into powders suitable for AM. This is because the powders have the required shape for the alloys to be used in AM (e.g., LPBF or directed energy deposition (DED)). In such embodiments, the powders have a volume average particle size of 10 to 200 μm (preferably measured by laser diffraction according to ASTM B822 (for small particles) and / or sieving according to ASTM B214 (for large particles)). The alloys can be formed into AM articles by known AM techniques, such as powder bed fusion. Because AM articles have a grain structure (i.e., polycrystalline rather than single crystal), attention must be paid to grain boundary morphology during alloy design, e.g., to ensure that grain boundaries do not become physical weaknesses in the alloy or are not susceptible to attack by oxidation. Therefore, alloys designed for single crystal applications may not be suitable for use as AM powders. In particular, certain elements are added to strengthen the grain boundaries in the present invention. Most importantly, carbon to strengthen the grain boundaries, and to a lesser extent (not in all embodiments), zirconium and boron to increase grain boundary strength. The volume average particle sizes suitable for various types of additive manufacturing processes (suitable for alloys) are as follows: Laser powder bed fusion: 10-60μm Electron beam powder bed fusion: 60~105μm Directed energy deposition: 45~150μm

[0139] The D10, D50 and D90 results below are typical results for a powder with a volume mean diameter of 35.8 μm. [Table A]

[0140] For laser powder bed fusion, D10 can range from 5-35 μm, D50 from 10-60 μm, and D90 from 45-80 μm. For electron beam powder bed fusion, D10 can range from 50-100 μm, D50 from 60-105 μm, and D90 from 80-125 μm. For directed energy deposition, D10 can range from 20-60 μm, D50 from 20-150 μm, and D90 from 100-200 μm.

[0141] Based on the description of the invention in this section, broad ranges of the invention are listed in Table 4. Table 4 also lists preferred and most preferred ranges. Table 4 lists the composition ranges, in wt. %, of the new designed alloys.

[0142] [Table 4]

[0143] (Example of the present invention) [Table 5] [Table 6]

[0144] Table 5 shows the nominal compositions, in mass percent, of newly designed high-γ' volume fraction nickel-base superalloys compared to the alloys listed in Table 1. Table 6 shows the phase fractions and figures of merit calculated by the "Alloy Design" software for the conventionally used high-γ' volume fraction nickel-base superalloys (Table 1) and the newly designed high-γ' volume fraction nickel-base superalloys compared to the alloys listed in Table 1.

[0145] Examples 1 and 2, which are examples of alloys of the present invention, are listed in Tables 5 and 6. These alloys possess high creep resistance due to their high γ' volume fraction and high creep figure of merit. As discussed later in this section, the measured creep results for the example alloys show that the alloys contain 1.1 wt.% or more titanium to enhance grain boundary strength and achieve a high level of creep resistance. This high creep resistance is achieved in combination with good oxidation and a high level of AM processability. The excellent oxidation resistance in Examples 1 and 2 is achieved by the high aluminum content (>4.5 wt.%), which forms a protective alumina scale at 1000°C. The low strain-age cracking index and low hot-tearing index result in superior printability compared to CM247.

[0146] Figure 14 compares creep results for AM-processed CM247 with the example alloys listed in Table 5 (Examples 1 and 2 were not tested to failure, while CM247 was). Figure 4 shows that the combinations of γ' volume fraction and creep figure of merit for the example alloys are predicted to yield comparable creep resistance. The results show that the inventive examples have lower creep rates than CM247 at 900°C / 200 MPa creep conditions. This higher creep resistance suggests that the grain boundary strengthening effect of the formation of stable titanium MC carbides reduces the creep rate of these novel alloys compared to CM247. CM247 contains 0.8% titanium by weight, while Examples 1 and 2 contain 1.2% and 1.5% titanium by weight, respectively. The beneficial effect is predicted to extend to at least 1.1% titanium by weight, and is observable at higher levels up to at least 6.0% by weight.

Claims

1. 4.0 to 6.0 mass% aluminum, 1.1 to 6.0 mass% titanium, 0.0 to 4.0 mass% niobium, 0.0 to 11.9 mass% tantalum, 2.0 to 12.7 mass% tungsten, 0.0 to 3.0 mass% molybdenum, 0.0 to 22.0 mass% cobalt, 6.0 to 16.7 mass% chromium, 0.02 to 0.35 mass% carbon, 0.001 to 0.2 mass% boron, 0.00 to 0.01 mass% zirconium, 0.0 to 3.0 mass% rhenium, 0.0 to 3.0 mass% ruthenium, 0.0 to 3.0 mass% iridium, 0.

1. A nickel-based alloy composition comprising 0 to 0.5% by mass of vanadium, 0.0 to 1.0% by mass of palladium, 0.0 to 1.0% by mass of platinum, 0.0 to 0.5% by mass of silicon, 0.0 to 0.1% by mass of yttrium, 0.0 to 0.1% by mass of lanthanum, 0.0 to 0.1% by mass of cerium, 0.0 to 0.003% by mass of sulfur, 0.0 to 0.25% by mass of manganese, 0.0 to 0.1% by mass of magnesium, 0.0 to 4.0% by mass of iron, 0.0 to 0.5% by mass of copper, 0.0 to 2.0% by mass of hafnium, and the balance being nickel and unavoidable impurities.

2. The mass percentages of niobium and tantalum contained in the alloy are W Ｎｂ , W Ｔａ The nickel-based alloy composition according to claim 1, which satisfies the following formula: 0.6≦0.3W Ｎｂ +0.15W Ｔａ Preferably, the following formula is satisfied: 0.625≦0.3W Ｎｂ +0.15W Ｔａ More preferably, the following formula is satisfied: 0.65≦0.3W Ｎｂ +0.15W Ｔａ

3. The mass percentages of aluminum, titanium, niobium, and tantalum contained in the alloy are respectively W Ａｌ , W Ｔｉ , W Ｎｂ and W Ｔａ The nickel-based alloy composition according to claim 1 or 2, which satisfies the following formula: 5.6≦W Ａｌ +0.5W Ｔｉ +0.3W Ｎｂ +0.15W Ｔａ ≦7.0 Preferably, the following formula is satisfied: 5.6≦W Ａｌ +0.5W Ｔｉ +0.3W Ｎｂ +0.15W Ｔａ ≦6.5

4. 4. A nickel-based alloy composition according to any one of claims 1 to 3, wherein the volume fraction of the gamma prime phase at 900°C is not more than 63%, preferably not more than 56%.

5. 5. The nickel-based alloy composition of claim 1, wherein the volume fraction of gamma prime phase at 900°C is 42% or more, preferably 43% or more, more preferably 45% or more, even more preferably 50% or more, even more preferably 57% or more, even more preferably 57% or more, and most preferably 60% or more.

6. The mass percentages of tungsten and molybdenum contained in the alloy are W Ｗ , W Ｍｏ The nickel-based alloy composition according to any one of claims 1 to 5, which satisfies the following formula: W Ｗ +0.65W Mo ≧4.0 Preferably, the following formula is satisfied: W Ｗ +0.65W Mo ≧6.0 More preferably, the following formula is satisfied: W Ｗ +0.65W Mo ≧8.0

7. 7. The nickel-based alloy composition of any one of claims 1 to 6, comprising, by weight, chromium at least 8.0%, preferably at least 8.5%, more preferably at least 9.0%, more preferably at least 9.5%, more preferably at least 9.6%, more preferably at least 9.75%, and most preferably at least 10.0%.

8. 8. A nickel-based alloy composition according to any one of claims 1 to 7, comprising, by weight, chromium in an amount up to 14.7%, preferably up to 13.8%.

9. 9. The nickel-based alloy composition of any one of claims 1 to 8, comprising, by weight, tantalum in an amount of up to 9.8%, preferably up to 9.2%, more preferably up to 7.1%, even more preferably up to 6.3%, even more preferably up to 5.5%, even more preferably up to 5.0%, more preferably up to 4.5%, and most preferably up to 4.0%.

10. 10. The nickel-based alloy composition of any one of claims 1 to 9, comprising, by weight, molybdenum in an amount not greater than 2.0%, preferably not greater than 1.8%, preferably not greater than 1.5%, more preferably not greater than 1.4%, and most preferably not greater than 1.3%.

11. 11. The nickel-based alloy composition of any one of claims 1 to 10, comprising, by weight, titanium at most 5.0%, preferably at most 4.2%, more preferably at most 3.4%, more preferably at most 3.0%, more preferably at most 2.5%, more preferably at most 2.0%, more preferably at most 1.5%, more preferably at most 1.4%, even more preferably at most 1.3%, even more preferably at most 1.35%, even more preferably at most 1.2%, and even more preferably between 1.1% and 1.25%.

12. 12. The nickel-based alloy composition of any one of claims 1 to 11, comprising, by weight, hafnium in an amount of up to 1.5%, preferably up to 1.2%, more preferably up to 1.1%.

13. 13. The nickel-based alloy composition of any one of claims 1 to 12, comprising, by weight, tungsten in an amount of up to 10.7%, preferably up to 9.5%, more preferably up to 9.0%, even more preferably up to 8.7%, even more preferably up to 8.5%, more preferably up to 8.0%, more preferably up to 7.6%, and most preferably up to 7.5%.

14. 14. The nickel-based alloy composition of any one of claims 1 to 13, comprising, by weight, niobium in an amount of up to 3.0%, preferably up to 2.0%.

15. 15. The nickel-based alloy composition according to claim 1, comprising, by mass %, 0.5% or less of at least one of platinum and palladium.

16. 16. The nickel-based alloy composition of any one of claims 1 to 15, comprising, by weight, aluminum in an amount of at least 4.3%, preferably at least 4.5%, more preferably at least 4.6%.

17. 17. The nickel-based alloy composition of any one of claims 1 to 16, comprising, by weight, aluminum in an amount of up to 5.6%, preferably up to 5.5%, more preferably up to 5.3%, even more preferably up to 5.2%, more preferably up to 5.1%, and most preferably up to 5.0%.

18. 18. The nickel-based alloy composition of any one of claims 1 to 17, comprising, by weight, cobalt in an amount of up to 15.0%, preferably up to 10.0%, more preferably up to 9.5%, more preferably up to 9.1%, more preferably up to 9.0%.

19. 19. A nickel-based alloy composition according to any one of the preceding claims, comprising, by weight, vanadium in an amount of up to 0.3%, preferably up to 0.1%.

20. 20. The nickel-based alloy composition of any one of claims 1 to 19, comprising, by weight, tantalum in an amount of at least 1.1%, preferably at least 2.0%, more preferably at least 2.5%.

21. 21. The nickel-based alloy composition of any one of claims 1 to 20, comprising, by weight, tungsten at least 2.7%, preferably at least 2.8%, more preferably at least 4.7%, even more preferably at least 5.1%, more preferably at least 5.2%, and most preferably at least 6.2%.

22. The mass percentages of niobium, tantalum, titanium, platinum, palladium, and aluminum contained in the alloy are respectively W Ｎｂ , W Ｔａ , W Ｔｉ , W Ｐｔ , W Ｐｄ and W Ａｌ 22. The nickel-based alloy composition according to claim 1, wherein the following formula is satisfied: W Ａｌ +0.5W Ｔｉ +0.3W Ｎｂ +0.15W Ｔａ +0.125W Ｐｔ +0.225W Ｐｄ ≦7.0 Preferably, the following formula is satisfied: W Ａｌ +0.5W Ｔｉ +0.3W Ｎｂ +0.15W Ｔａ +0.125W Ｐｔ +0.225W Ｐｄ ≦6.5

23. The mass percentages of tantalum and tungsten contained in the alloy are W Ｔａ and W Ｗ 23. The nickel-based alloy composition according to claim 1, wherein the following formula is satisfied: W Ｗ +W Ｔａ ≦13.9 Preferably, the following formula is satisfied: W Ｗ +W Ｔａ ≦11.8

24. 24. The nickel-based alloy composition of any one of claims 1 to 23, comprising, by weight, titanium in an amount of at least 1.2%, preferably at least 1.3%.

25. 25. The nickel-based alloy composition of any one of claims 1 to 24, comprising, by weight, hafnium at least 0.1%, preferably at least 0.2%, more preferably at least 0.25%, even more preferably at least 0.3%, even more preferably at least 0.5%, even more preferably at least 0.6%, even more preferably at least 0.8%, or between 0.8 and 1.2%.

26. 26. The nickel-based alloy composition of any one of claims 1 to 25, comprising, by weight, cobalt in an amount of at least 5.5%, preferably at least 6.0%, more preferably at least 8.0%, more preferably at least 9.0%, more preferably at least 10.0%.

27. 27. The nickel-based alloy composition of any one of claims 1 to 26, comprising, by weight, niobium at least 0.05%, preferably at least 0.5%, more preferably at least 1.0%.

28. 28. The nickel-based alloy composition of any one of claims 1 to 27, comprising, by weight, at least 0.1%, preferably at least 0.2%, more preferably at least 0.5% molybdenum.

29. 7.1% by weight or less of tantalum, 5.3% by weight or less of aluminum, and preferably 8.0% by weight or more of cobalt, more preferably the weight percentages of tantalum and tungsten contained in the alloy are respectively W Ｔａ and W Ｗ The nickel-based alloy composition according to claim 1 or 2, which satisfies the following formula: W Ｗ +W Ｔａ ≦13.9

30. 30. The nickel-based alloy composition of any one of claims 1 to 29, comprising, by weight, zirconium in an amount of up to 0.005%, preferably up to 0.002%, more preferably up to 0.0015%.

31. 31. The nickel-based alloy composition of any one of claims 1 to 30, comprising, by weight, carbon in an amount of up to 0.2%, preferably up to 0.15%, more preferably up to 0.10%.

32. 32. The nickel-based alloy composition of any one of claims 1 to 31, comprising, by weight, boron in an amount of up to 0.03%, preferably up to 0.02%, even more preferably up to 0.018%, more preferably up to 0.015%, more preferably up to 0.012%.

33. 33. The nickel-based alloy composition of any one of claims 1 to 32, comprising, by weight, boron at least 0.005%, preferably at least 0.006%, more preferably at least 0.008%, and most preferably at least 0.10%.

34. 34. The nickel-based alloy composition of any one of claims 1 to 33, comprising, by weight, rhenium in an amount up to 2.9%, preferably up to 2.5%, more preferably up to 2.0%, and most preferably up to 1.5%.

35. 35. The nickel-based alloy composition of any one of claims 1 to 34, comprising, by weight, rhenium in an amount of at least 0.1%, preferably at least 0.2%, more preferably at least 0.3%, and even more preferably at least 0.8%.

36. 36. The nickel-based alloy composition of any one of claims 1 to 35, comprising, by weight, silicon in an amount of up to 0.2%, preferably up to 0.1%, more preferably up to 0.05%.

37. 37. A nickel-based alloy composition according to any one of the preceding claims, comprising, by weight, carbon in an amount of at least 0.06%, preferably at least 0.07%.

38. 10. The nickel-base alloy composition of claim 1, comprising the alloy composition of Example 1 of Table 5.

39. 39. The nickel-based alloy composition of any one of claims 1 to 38, comprising, in mass %, at least 10.0% chromium, preferably 10.1 to 10.5% chromium, at most 5.0% aluminium, preferably at most 4.95% aluminium, more preferably 4.85 to 4.95% aluminium, and at least 0.001% zirconium, preferably 0.002 to 0.004% zirconium.

40. 40. A nickel-based alloy composition according to any one of the preceding claims, comprising, in mass %, at least 6% cobalt, preferably at least 7% cobalt, more preferably 8-9% cobalt.

41. A powder of a nickel-based alloy according to any one of claims 1 to 40, suitable for additive manufacturing.

42. The powder according to claim 41, wherein the powder has a volume average particle size of 10 to 200 μm as measured by laser diffraction in accordance with ASTM B822.

43. 41. An additively manufactured object made from an alloy according to any one of claims 1 to 40.

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