NICKEL-BASED SUPERALLOY

Abstract

A Nickel-based superalloy, whose composition includes, in percent by weight of the total composition: Chromium: 10.0-11.25; Cobalt: 11.2-13.7; Molybdenum: 3.1-3.8; Tungsten: 3.1-3.8; Aluminium: 2.9-3.5; Titanium: 4.6-5.6; Niobium: 1.9-2.3; Hafnium: 0.25-0.35; Zirconium: 0.040-0.060; Carbon: 0.010-0.030; Boron: 0.01-0.030; Nickel: remainder as well as unavoidable impurities; the composition being free of tantalum.

Claims

1. A Nickel-based superalloy, whose composition comprises, in percent by weight of the total composition: Chromium: 10.0-11.25 Cobalt: 11.2-13.7 Molybdenum: 3.1 3.8 Tungsten: 3.1-3.8 Aluminium: 2.9-3.5 Titanium: 4.6-5.6 Niobium: 1.9-2.3 Hafnium: 0.25-0.35 Zirconium: 0.040-0.060 Carbon: 0.010-0.030 Boron: 0.01-0.030 Nickel: remainder as well as unavoidable impurities; the composition being free of tantalum.

2. The nickel-based superalloy according to claim 1, which has a volume fraction of gamma prime phase of between 52% and 60%.

3. The nickel-based superalloy according to claim 2, wherein a sum of the contents of Al, Ti and Nb in atomic % is between 13 and 15.

4. The nickel-based superalloy according to claim 2, wherein a ratio of contents (Ti+Nb)/A1 in atomic % is less than 1.2.

5. The nickel-based superalloy according to claim 1, wherein a sum of the contents of W, Mo, Cr and Co, in atomic %, is greater than or equal to 25.5 and less than or equal to 29.5.

6. The nickel-based superalloy according to claim 1, wherein a sum of the contents of W and Mo, in atomic %, is greater than or equal to 2.3 and less than or equal to 3.9.

7. A powder of a superalloy according to claim 1.

8. A method for manufacturing a part made of superalloy according to claim 1, comprising the following steps: a - forging, b - gradient heat treatment of the part obtained in step a), c - final heat treatment of the entire dual-microstructure part obtained in step b) d - recovery of the part obtained in step c).

9. The method according to claim 8, wherein step b) of gradient heat treatment of the part obtained in step a) includes: b1 - a first heating of a region of the part at a first temperature (Ti) greater than a solvus temperature of a gamma prime phase of said superalloy and less than a melting temperature of said superalloy.

10. The method according to claim 8, wherein step c) of final heat treatment comprises the following successive steps: c1- solution heat treatment of the entire part obtained in step b) at a temperature (T2) less than the solvus temperature of the gamma prime phase of said superalloy; c2 - quenching treatment of the entire part obtained in step c1); c3 - tempering treatment of the entire part obtained in step c2).

11. A part made of superalloy according to claim 1, having a dual microstructure.

12. The part according to claim 11, wherein the part is a turbomachine part.

13. The Nickel-based superalloy according to claim 1, wherein the composition comprises, in percent by weight of the total composition: Chromium: 10.0-11.0; Cobalt: 12.0-13.0; Molybdenum: 3.3-3.7; Tungsten: 3.1-3.5; Aluminium: 3.2-3.5; Titanium: 4.6-5.0; Niobium: 1.9-2.0; Hafnium: 0.25-3.0; Zirconium: 0.050-0.060; Carbon: 0.015-0.025; Boron: 0.01-0.02; Nickel: remainder as well as unavoidable impurities; the composition being free of tantalum.

14. The Nickel-based superalloy according to claim 1, wherein the composition essentially consists of, in percent by weight of the total composition: Chromium: 10.0-11.25; Cobalt: 11.2-13.7; Molybdenum: 3.1-3.8; Tungsten: 3.1-3.8; Aluminium: 2.9-3.5; Titanium: 4.6-5.6; Niobium: 1.9-2.3; Hafnium: 0.25-0.35; Zirconium: 0.040-0.060; Carbon: 0.010-0.030; Boron: 0.01-0.030; Nickel: remainder as well as unavoidable impurities; the composition being free of tantalum.

15. The Nickel-based superalloy according to claim 13, wherein the composition essentially consists of, in percent by weight of the total composition: Chromium: 10.0-11.0; Cobalt: 12.0-13.0; Molybdenum: 3.3-3.7; Tungsten: 3.1-3.5; Aluminium: 3.2-3.5; Titanium: 4.6-5.0; Niobium: 1.9-2.0; Hafnium: 0.25-3.0; Zirconium: 0.050-0.060; Carbon: 0.015-0.025; Boron: 0.01-0.02; Nickel: remainder as well as unavoidable impurities; the composition being free of tantalum.

16. The method according to claim 10, wherein step c3) is carried out at a temperature greater than 760° C.

17. The part according to claim 11, wherein the part is a turbine part.

18. The part according to claim 11, wherein the part is a turbine disc, a compressor disc, a ring, a flange or a turbine housing.

Description

[0110] FIG. 1 shows the comparison of the elastic limit (in MPa as a function of the temperature in ° C. according to standard NF EN 2002-001/06) of the superalloy according to Example 1 with other alloys for discs made by powder metallurgy of the prior art.

[0111] FIG. 2 shows the comparison of the mechanical strength (in MPa as a function of the temperature in ° C. according to standard NF EN 2002-001/06) of the superalloy according to Example 1 with other alloys for discs made by powder metallurgy of the prior art.

EXAMPLE

[0112] A nickel-based superalloy according to the invention (Example 1) was manufactured according to the following method: vacuum casting an ingot, then atomising this ingot under argon, sieving at 53 μm, placing the powder in a container with degassing, then hot extruding of these powders in the form of a bar. The measured density of the alloy is 8240 kg/m.sup.3. The volume measurement is carried out by helium pycnometry and the mass measurement is carried with a precision balance, then the density is calculated using these two measurements. The alloy contains 56.5% gamma prime phase.

[0113] The manufactured alloy has the chemical composition, in percent by mass, indicated in Table 1 above.

[0114] The solvus temperature of the gamma prime phase for this alloy is 1195° C.

[0115] A portion of the bar was then subjected to treatment at a temperature of 1200° C., thus greater than 1195° C. for a duration of 2 hours (supersolvus treatment) then cooled at 30° C./min, followed by treatment at a temperature of 1165° C., thus less than 1195° C. for a duration of 2 hours (subsolvus treatment) followed by quenching at 100° C./min and tempering at a temperature of 800° C., thus greater than 760° C. for a duration of 8 hours (thermal cycle representative of that of the rim region of a disc). The resulting microstructure has a grain size measured by the intercept method of 24 μm measured at the surface of the sample by EBSD images (Electron Back Scattered Diffraction), this size thus being greater than 15 μm.

[0116] Another portion of the bar was only subjected to the subsolvus treatment is followed by the quenching and tempering treatment, both carried out at the same temperature and for the same duration as first portion of the bar (thermal cycle representative of that of the bore region of a disc). This microstructure has a grain size of 3.5 μm measured by the intercept method, this size thus being less than 15 μm.

[0117] Tensile and creep tests were performed on samples taken from these two bars respectively according to standards NF EN 2002-001/06 and NF EN ISO 24 Aug. 2009.

[0118] The results were compared to the compositions of the prior art produced by powder metallurgy and homogeneous heat treatment, having the composition in percent by mass as indicated in Table 2 below:

TABLE-US-00002 TABLE 2 Alloy A Rene88 SMO43 (N19 according to (commercially commercially % mass ME501 EP2628810 available) available) Ni Base Base Base Base Cr 12 10.18 16 13.3 Co 18 20.49 13 12.2 Mo 2.9 3.61 4 4.6 W 3.0 2.22 4 3.0 Nb 1.5 2.08 0.7 1.5 Al 3.0 3.53 2.1 2.9 Ti 3.0 3.03 3.7 3.6 C 0.05 0.035 0.05 0.015 B 0.03 0.040 0.015 0.01 Zr 0.05 0.058 0.05 0.05 Hf 0.4 <0.01 0 0.25 Ta 4.8 4.76 0 0

[0119] The tensile results (elastic limit and mechanical strength as a function of temperature) are indicated in FIGS. 1 and 2.

[0120] The creep results are indicated in Table 3 below:

TABLE-US-00003 TABLE 3 Temperature Stress Time to 0.2% elongation Alloy (° C.) (MPa) (hours) SMO43 (40-60 μm) 750 500 Approximately 150 Example 1 (10- 750 500 >179 40 μm) 850 200 >37

[0121] The tensile results for the alloy according to the invention (Example 1) are close to or even better than those for the alloys ME501 and Alloy A, these two alloys being loaded with tantalum. The tensile results are also better than for SM043 (N19), additionally producing a gain in the density of the alloy. More specifically, SM043 (N19) has a density of 8340 kg/m.sup.3. Moreover, the alloy according to the invention has undergone a final relatively hot tempering (>760° C.) relative to the alloys SM043 (final tempering at 750° C.) and ME501 (final tempering at 760° C.), in order to stabilise its microstructure at high temperature but slightly lowering the tensile strength and creep resistance. The solid squares and circles in FIGS. 1 and 2 represent the mechanical properties of the part after dual-structure treatment, and this as a function of the operating temperature seen by each region (the transition is located at 750° C.): the fine-grain region (solid squares) has a resistance optimised for temperatures less than 750° C., and the coarse-grain region (solid circles) has a resistance optimised for the temperatures greater than 750° C.

[0122] The results for elongation creep show the good resistance of the alloy according to the invention despite a finer grain size and a hotter tempering than SM043. The alloy can also withstand excursions to very high temperatures such as 850° C.