Process for manufacturing a part made of nickle-based superalloy containing hafnium

Abstract

The invention relates to a process for manufacturing a part made of nickel-based monocrystalline superalloy containing hafnium. This process is noteworthy in that it comprises the following successive steps consisting in: —manufacturing a nickel-based monocrystalline superalloy that is not doped with hafnium, —manufacturing a part from this superalloy, —directly depositing on said part a layer of hafnium having a thickness of between 50 nm and 800 nm, —carrying out a diffusion treatment of the hafnium so as to form an interdiffusion layer at the surface of said part and to thus obtain a part made of nickel-based monocrystalline superalloy containing hafnium.

Claims

1. A process for manufacturing a hafnium-containing nickel-based single-crystal superalloy part, wherein the process comprises the following successive steps: manufacturing a nickel-based, non-hafnium-doped, single-crystal superalloy, manufacturing a part from this superalloy, depositing, directly on said part, a layer of nanocrystalline or microcrystalline hafnium having a thickness comprised between 50 nm and 800 nm, carrying out a hafnium diffusion treatment so as to form an interdiffusion layer on the surface of said part, and thereby obtain a hafnium-containing nickel-based single-crystal superalloy part.

2. The process according to claim 1, wherein the deposition of the layer of hafnium is carried out by physical vapour deposition (PVD).

3. The process according to claim 2, wherein the deposition of the layer of hafnium is carried out by cathode sputtering.

4. The process according to claim 1, wherein the deposition of the layer of hafnium is carried out by chemical vapour deposition (CVD).

5. The process according to claim 1, wherein the layer of hafnium deposited on said part has a thickness comprised between 50 nm and 300 nm.

6. The process according to claim 1, wherein the hafnium diffusion treatment is carried out under vacuum or under a mixture of 95% by volume argon and 5% by volume helium, by carrying out a temperature increase until bringing said part to a temperature comprised between 500° C. and 1,200° C., maintaining this temperature for 1 hour to 4 hours and cooling said part until it returns to room temperature.

7. The process according to claim 1, wherein the non-hafnium-doped nickel-based single-crystal superalloy comprises in mass percent 5.2% aluminium, 6.5% cobalt, 7.8% chromium, 2% molybdenum, 7.9% tantalum, 1.1% titanium, 5.7% tungsten and the remainder nickel.

8. The process according to claim 1, wherein the non-hafnium-doped nickel-based single-crystal superalloy comprises in mass percent 5.6% aluminium, 9.6% cobalt, 6.5% chromium, 0.6% molybdenum, 3% rhenium, 6.5% tantalum, 1% titanium, 6% tungsten and the remainder nickel.

9. The process according to claim 1, wherein the non-hafnium-doped nickel-based single-crystal superalloy comprises in mass percent 5.73% aluminium, 9.6% cobalt, 3.46% chromium, 0.6% molybdenum, 4.9% rhenium, 8.3% tantalum, 0.9% titanium, 5.5% tungsten and the remainder nickel.

10. The process according to claim 1, wherein the non-hafnium-doped nickel-based single-crystal superalloy comprises in mass percent 5.7% aluminium, 3% cobalt, 2% chromium, 0.4% molybdenum, 6% rhenium, 8% tantalum, 0.2% titanium, 5% tungsten, 0.1% niobium and the remainder nickel.

11. The process according to claim 1, wherein the non-hafnium-doped single-crystal nickel-based superalloy comprises in mass percent 5.8% aluminium, 12.5% cobalt, 4.2% chromium, 1.4% molybdenum, 5.4% rhenium, 7.2% tantalum, 6% tungsten and the remainder nickel.

12. The process according to claim 1, wherein the non-hafnium-doped nickel-based single-crystal superalloy comprises in mass percent 6% aluminium, less than 0.2% cobalt, 4% chromium, 1% molybdenum, 4% rhenium, 5% tantalum, 0.5% titanium, 5% tungsten, 4% ruthenium and the remainder nickel.

13. The process according to claim 1, wherein the non-hafnium-doped nickel-based single-crystal superalloy comprises nickel, aluminium, cobalt, chromium, molybdenum, tantalum and tungsten.

14. The process according to claim 1, wherein the non-hafnium-doped nickel-based single-crystal superalloy comprises in mass percent about 5.2% to 6% aluminium, about 0.2% to 12.5% cobalt, about 2% to 7.8% chromium, about 0.4% to 2% molybdenum, about 5% to 8% tantalum and about 5% to 6% tungsten.

15. The process according to claim 1, wherein the part is manufactured from the non-hafnium-doped nickel-based single-crystal superalloy by casting or additive manufacturing.

16. The process according to claim 1, wherein the deposited layer of hafnium is a layer containing at least 99.99 atomic percent of hafnium.

17. The process according to claim 1, wherein after the manufacturing step of the part from the non-hafnium-doped nickel-based single-crystal superalloy and before the depositing step of the layer of hafnium, the manufactured part is subjected to a solutioning treatment.

18. The process according to claim 17, wherein the solutioning treatment consists of a first step of temperature increase until reaching a temperature of about 1,100° C. for a period comprised between a few minutes and 4 hours, followed by a second step of temperature increase until reaching a temperature of about 1,200° C. for a period comprised between a few minutes and 4 hours, and finally a third step of temperature increase until reaching a temperature of about 1,300° C. for a period comprised between a few minutes and 4 hours.

19. The process according to claim 1, wherein the deposition of the layer of hafnium is carried out by a technique selected from low-pressure chemical vapour deposition (LPCVD), chemical vapour aluminizing (CVA), ultra-high vacuum chemical vapour deposition (UHVCVD), plasma enhanced chemical vapour deposition (PECVD), atmospheric pressure chemical vapour deposition (APCVD), and atomic layer chemical vapour deposition (ALCVD).

Description

DETAILED DESCRIPTION

(1) The process in accordance with the invention consists, first, in manufacturing a nickel-based, non-hafnium-doped, single-crystal superalloy. “Non-hafnium-doped” means hafnium-free.

(2) Table 1 below gives several preferential exemplary superalloys useful in the process in accordance with the invention. They are identified by the letters A to F. Other non-hafnium-doped nickel-based single-crystal superalloys may also be used.

(3) TABLE-US-00001 TABLE 1 Exemplary hafnium-free nickel-based single-crystal superalloys Alloy elements (mass percentages) Ni Al Co Cr Mo Re Ta Ti W Cb Ru A Remainder 5.2 6.5 7.8 2 0 7.9 1.1 5.7 B Remainder 5.6 9.6 6.5 0.6 3 6.5 1 6 C Remainder 5.73 9.6 3.46 0.6 4.87 8.28 0.86 5.5 D Remainder 5.7 3 2 0.4 6 8 0.2 5 0.1 E Remainder 5.8 12.5 4.2 1.4 5.4 7.2 0 6 F Remainder 6 <0.2 4 1 4 5 0.5 5 4

(4) The term “remainder” corresponds, for each superalloy, to the residual mass percentage to reach 100% with the various other components mentioned.

(5) A part with a desired shape is then formed from such a superalloy, for example by casting or additive manufacturing.

(6) Preferably, the resulting part is then subjected to a solutioning treatment, as described above in the introduction.

(7) Preferably, this treatment consists of a first step of temperature increase until reaching a temperature of about 1100° C. for a period comprised between a few minutes and 4 hours, followed by a second step of temperature increase until reaching a temperature of about 1200° C. for a period comprised between a few minutes and 4 hours, and finally a third step of temperature increase until reaching a temperature of about 1300° C. for a period comprised between a few minutes and 4 hours.

(8) A layer of hafnium, i.e. either a layer of pure hafnium (100 atomic % hafnium) or a layer containing at least 99.99 atomic % hafnium, is then deposited on the part thus manufactured. This layer is preferably nanocrystalline or microcrystalline. Preferably, this layer has a thickness comprised between 50 nm and 800 nm, more preferably comprised between 50 nm and 300 nm.

(9) The deposition of this layer of hafnium can be carried out by physical vapour deposition (PVD), preferably by cathode sputtering. This allows good control of the deposited thickness.

(10) Mention may also be made of the use of electron beam physical vapour deposition (EBPVD), evaporation, pulsed laser ablation or cathode sputtering. The latter technique has the advantage of allowing the formation of dense films of nanometric or micrometric thickness and having superior adhesion to the preceding layer than that obtained with other deposition techniques.

(11) PVD is carried out inside an enclosure containing the part and one or more targets corresponding to the material(s) to be deposited, here notably hafnium. Under the application of a potential difference between the reactor walls and the target(s), a plasma is formed whose positive species are attracted to the cathode (target) and collide therewith. The atoms of the target(s) are sputtered and then condense on said part.

(12) Preferably, the deposition conditions are as follows: Heating during deposition: from 100 to 900° C. Pressure: from 0.1 Pa to 1 Pa Power density: 2 to 15 W/cm.sup.2 Polarization: −500V to −150V

(13) Ion bombardment is carried out for 10 to 30 minutes between −200V and 500V.

(14) Deposition of the layer of hafnium can also be carried out by chemical vapour deposition (CVD).

(15) Examples of chemical vapour deposition (CVD) techniques include: plasma enhanced chemical vapour deposition (PECVD), low-pressure chemical vapour deposition (LPCVD), ultra-high vacuum chemical vapour deposition (UHVCVD), atmospheric pressure chemical vapour deposition (APCVD), atomic layer chemical vapour deposition (ALCVD), chemical vapour aluminizing (CVA).

(16) Said part is then subjected to a hafnium diffusion treatment, so as to form, on the surface of said part, an interdiffusion layer in which hafnium is present.

(17) Preferably, the diffusion treatment is carried out by placing the part coated with the layer of hafnium inside an enclosure, bringing it under vacuum or introducing within it an atmosphere containing a mixture of 95% by volume argon and 5% by volume helium, and then carrying out the heat treatment described below.

(18) Preferably, this heat treatment comprises a phase of temperature increase until a temperature comprised between 500° C. and 1200° C. is reached, a phase of maintaining this temperature stage for a period of 1 hour to 4 hours and a cooling phase which consists in reducing the temperature inside the enclosure until it returns to room temperature.

(19) The process in accordance with the invention has many advantages, which are listed below.

(20) During the first step of the process, the production of a non-hafnium-doped nickel-based single-crystal superalloy and its use for manufacturing a part do not present difficulties.

(21) In contrast, in the state of the art (hafnium-doped superalloy), the shaping of the part, notably by casting, resulted, during its solidification, in hafnium losses that differed according to the part's geometry or solidification time. Similarly, this part was at risk of oxidizing (formation of hafnium oxide). This is not the case with the process of the invention since there is no hafnium at this stage.

(22) During the solutioning step, the homogenization of the part's components and the re-solutioning of the superalloy are optimal.

(23) During chemical attacks carried out as part of the non-destructive testing of parts, there is no preferential attack of residual eutectics.

(24) Finally, the subsequent deposition of the layer of hafnium and its diffusion result in the formation of a more robust part, with better mechanical strength via almost complete or improved solutioning of the eutectics and better resistance to oxidation and corrosion.