EP3911773B1 - Nickel based alloy with low density and mechanical and environmental strength at high temperature - Google Patents

Description

Technical area

The present invention relates to the general field of nickel-based superalloys for turbomachines, in particular for stationary blades, also called distributors or rectifiers, or moving blades, or even ring segments.

Prior technique

Nickel-based superalloys are generally used for the hot parts of turbomachines, that is to say the parts of the turbomachines located downstream of the combustion chamber. WO 2018/078269 A1 discloses a nickel-based superalloy suitable for the manufacture of blades for a turbomachine.

Nickel-based superalloys have the main advantages of combining both high creep resistance at temperatures between 650°C and 1200°C, as well as resistance to oxidation and corrosion.

The resistance to high temperatures is mainly due to the microstructure of these materials, which is composed of a γ-Ni matrix of face-centered cubic crystalline structure (CFC) and ordered hardening precipitates γ'-Ni ₃ Al of structure L1 ₂ . Certain grades of nickel-based superalloys are used for the manufacture of monocrystalline parts.

Disclosure of Invention

The object of the present invention is to propose nickel-based superalloy compositions which make it possible to improve the mechanical strength, and in particular the creep resistance.

Another object of the present invention is to provide superalloy compositions which make it possible to improve the resistance to the environment, and in particular the resistance to corrosion and the resistance to oxidation.

The present invention also aims to provide superalloy compositions which have a reduced density.

According to a first aspect, the invention proposes a nickel-based superalloy comprising, in mass percentages, 6 to 8% aluminum, 12 to 15% cobalt, 4 to 8% chromium, 0 to 0.2% hafnium, 0.5-4% molybdenum, 3.5-6% rhenium, 4-6% tantalum, 1-3% titanium, 0-2% tungsten, 0-0.1% silicon, the balance being made up of nickel and the inevitable impurities.

A nickel-based alloy is defined as an alloy in which the mass percentage of nickel is predominant.

Unavoidable impurities are defined as elements which are not intentionally added to the composition and which are added with other elements. Among the unavoidable impurities, mention may in particular be made of carbon (C) or sulfur (S).

The nickel-based superalloy according to the invention has good microstructural stability at temperature, thus making it possible to obtain high mechanical characteristics at temperature.

The nickel-based superalloy according to the invention has improved corrosion resistance and oxidation resistance.

The nickel-based superalloy according to the invention makes it possible to reduce the sensitivity to the formation of foundry defects.

The nickel-based superalloy according to the invention makes it possible to have a density of less than 8.4 g.cm ^-3 .

According to a possible variant, the superalloy may comprise, in mass percentages, 6 to 8% aluminum, 12 to 15% cobalt, 4 to 8% chromium, 0 to 0.2% hafnium, 0.5 to 4 % molybdenum, 3.5-6% rhenium, 4-6% tantalum, 1-3% titanium, 0-2% tungsten, 0-0.05% silicon, balance nickel and unavoidable impurities.

Furthermore, the superalloy may comprise, in mass percentages, 6 to 8% aluminum, 12 to 15% cobalt, 4 to 8% chromium, 0 to 0.15% hafnium, 0.5 to 4% molybdenum, 3.5-6% rhenium, 4-6% tantalum, 1-3% titanium, 0-2% tungsten, 0-0.1% silicon, balance nickel and impurities inevitable.

According to a possible variant, the superalloy may comprise, in mass percentages, 6.5 to 7.5% aluminum, 12 to 15% cobalt, 4.5 to 7.5% chromium, 0 to 0.2% hafnium, 0.5 to 3.5% molybdenum, 3.5 to 5.5% rhenium, 4.5 to 5.5% tantalum, 1.5 to 2.5% titanium, 0 to 1 .5% tungsten, 0 to 0.1% silicon, the balance consisting of nickel and the inevitable impurities.

According to a possible variant, the superalloy may also comprise, in mass percentages, 6.5 to 7.5% aluminum, 13 to 15% cobalt, 4.5 to 5.5% chromium, 0 to 0.2 % hafnium, 1.5-2.5% molybdenum, 4.5-5.5% rhenium, 4.5-5.5% tantalum, 1.5-2.5% titanium, 0, 5 to 1.5% tungsten, the balance consisting of nickel and inevitable impurities.

According to a possible variant, the superalloy may comprise, in mass percentages, 6.5 to 7.5% aluminum, 13 to 15% cobalt, 4.5 to 5.5% chromium, 0 to 0.15% hafnium, 1.5-2.5% molybdenum, 4.5-5.5% rhenium, 4.5-5.5% tantalum, 1.5-2.5% titanium, 0.5 1.5% tungsten, the balance consisting of nickel and unavoidable impurities.

According to a possible variant, the superalloy may comprise, in mass percentages, 6.5 to 7.5% aluminum, 13 to 15% cobalt, 4.5 to 5.5% chromium, 0 to 0.1% hafnium, 1.5-2.5% molybdenum, 4.5-5.5% rhenium, 4.5-5.5% tantalum, 1.5-2.5% titanium, 0.5 1.5% tungsten, the balance consisting of nickel and unavoidable impurities.

According to a possible variant, the superalloy may comprise, in mass percentages, 6.5 to 7.5% aluminum, 13 to 15% cobalt, 4.5 to 5.5% chromium, 1.5 to 2, 5% molybdenum, 4.5-5.5% rhenium, 4.5-5.5% tantalum, 1.5-2.5% titanium, 0.5-1.5% tungsten, 0 to 0.1% silicon, the balance consisting of nickel and the inevitable impurities.

According to a possible variant, the superalloy may comprise, in mass percentages, 6.5 to 7.5% aluminum, 13 to 15% cobalt, 4.5 to 5.5% chromium, 0 to 0.1% hafnium, 1.5-2.5% molybdenum, 4.5-5.5% rhenium, 4.5-5.5% tantalum, 1.5-2.5% titanium , 0.5 to 1.5% tungsten, 0 to 0.1% silicon, the balance consisting of nickel and inevitable impurities.

The superalloy may also comprise, in mass percentages, 6.5 to 7.5% aluminum, 13 to 15% cobalt, 4.5 to 5.5% chromium, 0 to 0.2% hafnium, 0.5-1.5% molybdenum, 4.5-5.5% rhenium, 4.5-5.5% tantalum, 1.5-2.5% titanium, balance nickel and unavoidable impurities.

According to a possible variant, the superalloy may comprise, in mass percentages, 6.5 to 7.5% aluminum, 12 to 14% cobalt, 5.5 to 6.5% chromium, 0 to 0.2% hafnium, 1.5-2.5% molybdenum, 4.5-5.5% rhenium, 4.5-5.5% tantalum, 1.5-2.5% titanium, balance being consisting of nickel and the inevitable impurities.

According to another possible variant, the superalloy may comprise, in mass percentages, 6.5 to 7.5% aluminum, 13 to 15% cobalt, 5.5 to 6.5% chromium, 0 to 0.2 % hafnium, 1.5-2.5% molybdenum, 4.5-5.5% rhenium, 4.5-5.5% tantalum, 1.5-2.5% titanium, balance consisting of nickel and inevitable impurities.

According to another possible variant, the superalloy may comprise, in mass percentages: 6.5 to 7.5% aluminum, 12 to 14% cobalt, 6.5 to 7.5% chromium, 0 to 0.2 % hafnium, 0.5-1.5% molybdenum, 4.5-5.5% rhenium, 4.5-5.5% tantalum, 1.5-2.5% titanium, balance consisting of nickel and inevitable impurities.

According to another possible variant, the superalloy may comprise, in mass percentages: 6.5 to 7.5% aluminum, 13 to 15% cobalt, 6.5 to 7.5% chromium, 0 to 0.2 % hafnium, 1.5-2.5% molybdenum, 3.5-4.5% rhenium, 4.5-5.5% tantalum, 1.5-2.5% titanium, balance consisting of nickel and inevitable impurities.

According to a possible variant, the superalloy may comprise, in mass percentages: 6.5 to 7.5% aluminum, 13 to 15% cobalt, 5.5 to 6.5% chromium, 0 to 0.2% hafnium, 2.5-3.5% molybdenum, 3.5-4.5% rhenium, 4.5-5.5% tantalum, 1.5-2.5% titanium, balance being consisting of nickel and the inevitable impurities.

According to a second aspect, the invention proposes a turbomachine part made of nickel-based superalloy according to any one of the preceding characteristics.

The part can be an element of an aircraft turbomachine turbine, for example a high-pressure turbine or a low-pressure turbine, or else a compressor element, and in particular a high-pressure compressor element.

According to an additional characteristic, the turbine or compressor part can be a blade, said blade being able to be a mobile blade or a stationary blade, or even a ring sector.

According to another feature, the turbomachine part is monocrystalline, preferably with a crystalline structure oriented along a <001> crystallographic direction.

According to a third aspect, the invention proposes a method for manufacturing a nickel-based superalloy turbomachine part according to any one of the preceding characteristics by foundry.

According to an additional characteristic, the method comprises a directed solidification step to form a single-crystal part.

Description of embodiments

The superalloy according to the invention comprises a nickel base with which are associated major addition elements.

The major addition elements include: cobalt Co, chromium Cr, molybdenum Mo, tungsten W, aluminum Al, tantalum Ta, titanium Ti, and rhenium Re.

The superalloy may also comprise minor addition elements, which are addition elements whose maximum percentage in the superalloy does not exceed 1% in mass percentage.

Minor addition elements include: hafnium Hf and silicon Si.

The nickel base superalloy comprises, in mass percentages, 6 to 8% aluminum, 12 to 15% cobalt, 4 to 8% chromium, 0 to 0.2% hafnium, 0.5 to 4% molybdenum, 3-6% rhenium, 4-6% tantalum, 1-3% titanium, 0-2% tungsten, 0-0.1% silicon, balance nickel and unavoidable impurities .

The nickel-based superalloy may also advantageously comprise, in mass percentages, 6 to 8% aluminum, 12 to 15% cobalt, 4 to 8% chromium, 0 to 0.2% hafnium, 0, 5-4% molybdenum, 3-6% rhenium, 4-6% tantalum, 1-3% titanium, 0-2% tungsten, 0-0.05% silicon, balance nickel and unavoidable impurities.

The nickel-based superalloy may also advantageously comprise, in mass percentages, 6 to 8% aluminum, 12 to 15% cobalt, 4 to 8% chromium, 0 to 0.1% hafnium, 0, 5-4% molybdenum, 3-6% rhenium, 4-6% tantalum, 1-3% titanium, 0-2% tungsten, 0-0.1% silicon, balance nickel and unavoidable impurities.

The nickel-based superalloy may also advantageously comprise, in mass percentages, 6 to 8% aluminum, 12 to 15% cobalt, 4 to 8% chromium, 0 to 0.05% hafnium, 0, 5-4% molybdenum, 3-6% rhenium, 4-6% tantalum, 1-3% titanium, 0-2% tungsten, 0-0.1% silicon, balance nickel and unavoidable impurities.

The nickel-based superalloy may also advantageously comprise, in mass percentages, 6 to 8% aluminum, 12 to 15% cobalt, 4 to 8% chromium, 0 to 0.1% hafnium (preferably 0 to 0.05% hafnium), 0.5 to 4% molybdenum, 3 to 6% rhenium, 4 to 6% tantalum, 1 to 3% titanium, 0 to 2% tungsten, 0 to 0 0.05% silicon, the balance consisting of nickel and the inevitable impurities.

The superalloy may also advantageously comprise, in mass percentages, 6.5 to 7.5% aluminum, 12 to 15% cobalt, 4.5 to 7.5% chromium, 0 to 0.2% hafnium, 0.5 to 3.5% molybdenum, 3.5 to 5.5% rhenium, 4.5 to 5.5% tantalum, 1.5 to 2.5% titanium, 0 to 1 .5% tungsten, 0 to 0.1% silicon, the balance consisting of nickel and the inevitable impurities.

Advantageously, the superalloy may comprise, in mass percentages, 6.5 to 7.5% aluminum, 12 to 15% cobalt, 4.5 to 7.5% chromium, 0 to 0.2% hafnium, 0.5-3.5% molybdenum, 3.5-5.5% rhenium, 4.5-5.5% tantalum, 1.5 to 2.5% titanium, 0 to 1.5% tungsten, 0 to 0.05% silicon, the balance being nickel and unavoidable impurities.

The superalloy may also advantageously comprise, in mass percentages, 6.5 to 7.5% aluminum, 12 to 15% cobalt, 4.5 to 7.5% chromium, 0 to 0.1% hafnium, 0.5 to 3.5% molybdenum, 3.5 to 5.5% rhenium, 4.5 to 5.5% tantalum, 1.5 to 2.5% titanium, 0 to 1 .5% tungsten, 0 to 0.1% silicon, the balance consisting of nickel and the inevitable impurities.

Preferably, the superalloy may comprise, in mass percentages, 6.5 to 7.5% aluminum, 12 to 15% cobalt, 4.5 to 7.5% chromium, 0 to 0.05% hafnium, 0.5-3.5% molybdenum, 3.5-5.5% rhenium, 4.5-5.5% tantalum, 1.5-2.5% titanium, 0-1, 5% tungsten, 0 to 0.1% silicon, the balance being made up of nickel and the inevitable impurities.

Preferably, the superalloy may comprise, in mass percentages, 6.5 to 7.5% aluminum, 12 to 15% cobalt, 4.5 to 7.5% chromium, 0 to 0.1% hafnium (preferably 0-0.05% hafnium), 0.5-3.5% molybdenum, 3.5-5.5% rhenium, 4.5-5.5% tantalum, 1.5 2.5% titanium, 0-1.5% tungsten, 0-0.05% silicon, the balance consisting of nickel and inevitable impurities.

The superalloy may also comprise, in mass percentages, 6.5 to 7.5% aluminum, 13 to 15% cobalt, 4.5 to 5.5% chromium, 0 to 0.2% hafnium, 1 .5-2.5% molybdenum, 4.5-5.5% rhenium, 4.5-5.5% tantalum, 1.5-2.5% titanium, 0.5-1.5 % tungsten, balance being nickel and unavoidable impurities.

The superalloy may also comprise, in mass percentages, 6.5 to 7.5% aluminum, 13 to 15% cobalt, 4.5 to 5.5% chromium, 0 to 0.15% hafnium, 1 .5-2.5% molybdenum, 4.5-5.5% rhenium, 4.5-5.5% tantalum, 1.5-2.5% titanium, 0.5-1.5 % tungsten, balance being nickel and unavoidable impurities.

The superalloy may also comprise, in mass percentages, 6.5 to 7.5% aluminum, 13 to 15% cobalt, 4.5 to 5.5% chromium, 0 to 0.1% hafnium, 1 .5-2.5% molybdenum, 4.5-5.5% rhenium, 4.5-5.5% tantalum, 1.5-2.5% of titanium, 0.5 to 1.5% of tungsten, the balance being made up of nickel and the inevitable impurities.

The superalloy may also include, in mass percentages, 6.5 to 7.5% aluminum, 13 to 15% cobalt, 4.5 to 5.5% chromium, 1.5 to 2.5% molybdenum , 4.5-5.5% rhenium, 4.5-5.5% tantalum, 1.5-2.5% titanium, 0.5-1.5% tungsten, 0-0.1 % of silicon, the balance being made up of nickel and the inevitable impurities.

The superalloy may also comprise, in mass percentages, 6.5 to 7.5% aluminum, 13 to 15% cobalt, 4.5 to 5.5% chromium, 0 to 0.1% hafnium, 1 .5-2.5% molybdenum, 4.5-5.5% rhenium, 4.5-5.5% tantalum, 1.5-2.5% titanium, 0.5-1.5 % tungsten, 0 to 0.1% silicon, balance consisting of nickel and inevitable impurities.

The superalloy may also include, in mass percentages, 6.5 to 7.5% aluminum, 13 to 15% cobalt, 4.5 to 5.5% chromium, 1.5 to 2.5% molybdenum , 4.5-5.5% rhenium, 4.5-5.5% tantalum, 1.5-2.5% titanium, 0.5-1.5% tungsten, the balance being nickel and inevitable impurities.

The superalloy may also comprise, in mass percentages, 6.5 to 7.5% aluminum, 13 to 15% cobalt, 4.5 to 5.5% chromium, 0 to 0.2% hafnium, 0 .5 to 1.5% molybdenum, 4.5 to 5.5% rhenium, 4.5 to 5.5% tantalum, 1.5 to 2.5% titanium, the balance being nickel and unavoidable impurities.

The superalloy may also include, in mass percentages, 6.5 to 7.5% aluminum, 13 to 15% cobalt, 4.5 to 5.5% chromium, 0.5 to 1.5% molybdenum , 4.5 to 5.5% rhenium, 4.5 to 5.5% tantalum, 1.5 to 2.5% titanium, the balance consisting of nickel and unavoidable impurities.

The superalloy may also comprise, in mass percentages, 6.5 to 7.5% aluminum, 12 to 14% cobalt, 5.5 to 6.5% chromium, 0 to 0.2% hafnium, 1 .5 to 2.5% molybdenum, 4.5 to 5.5% rhenium, 4.5 to 5.5% tantalum, 1.5 to 2.5% titanium, the balance being nickel and unavoidable impurities.

The superalloy may also comprise, in mass percentages, 6.5 to 7.5% aluminum, 12 to 14% cobalt, 5.5 to 6.5% chromium, 1.5 to 2.5% molybdenum, 4.5-5.5% rhenium, 4.5-5.5% tantalum, 1.5-2.5% titanium, the balance being nickel and unavoidable impurities.

The superalloy may also comprise, in mass percentages, 6.5 to 7.5% aluminum, 13 to 15% cobalt, 5.5 to 6.5% chromium, 0 to 0.2% hafnium, 1 .5 to 2.5% molybdenum, 4.5 to 5.5% rhenium, 4.5 to 5.5% tantalum, 1.5 to 2.5% titanium, the balance being nickel and unavoidable impurities.

The superalloy may also include, in mass percentages, 6.5 to 7.5% aluminum, 13 to 15% cobalt, 5.5 to 6.5% chromium, 1.5 to 2.5% molybdenum , 4.5 to 5.5% rhenium, 4.5 to 5.5% tantalum, 1.5 to 2.5% titanium, the balance consisting of nickel and unavoidable impurities.

The superalloy may also comprise, in mass percentages, 6.5 to 7.5% aluminum, 12 to 14% cobalt, 6.5 to 7.5% chromium, 0 to 0.2% hafnium, 0 .5 to 1.5% molybdenum, 4.5 to 5.5% rhenium, 4.5 to 5.5% tantalum, 1.5 to 2.5% titanium, the balance being nickel and unavoidable impurities.

The superalloy may also include, in mass percentages, 6.5 to 7.5% aluminum, 12 to 14% cobalt, 6.5 to 7.5% chromium, 0.5 to 1.5% molybdenum , 4.5 to 5.5% rhenium, 4.5 to 5.5% tantalum, 1.5 to 2.5% titanium, the balance consisting of nickel and unavoidable impurities.

The superalloy may also comprise, in mass percentages, 6.5 to 7.5% aluminum, 13 to 15% cobalt, 6.5 to 7.5% chromium, 0 to 0.2% hafnium, 1 .5 to 2.5% molybdenum, 3.5 to 4.5% rhenium, 4.5 to 5.5% tantalum, 1.5 to 2.5% titanium, the balance being nickel and unavoidable impurities.

The superalloy may also include, in mass percentages, 6.5 to 7.5% aluminum, 13 to 15% cobalt, 6.5 to 7.5% chromium, 1.5 to 2.5% molybdenum , 3.5 to 4.5% rhenium, 4.5 to 5.5% tantalum, 1.5 to 2.5% titanium, the balance consisting of nickel and unavoidable impurities.

The superalloy may also comprise, in mass percentages, 6.5 to 7.5% aluminum, 13 to 15% cobalt, 5.5 to 6.5% chromium, 0 to 0.2% hafnium, 2 .5 to 3.5% molybdenum, 3.5 to 4.5% rhenium, 4.5 to 5.5% tantalum, 1.5 to 2.5% titanium, the balance being nickel and unavoidable impurities.

The superalloy may also include, in mass percentages, 6.5 to 7.5% aluminum, 13 to 15% cobalt, 5.5 to 6.5% chromium, 2.5 to 3.5% molybdenum , 3.5 to 4.5% rhenium, 4.5 to 5.5% tantalum, 1.5 to 2.5% titanium, the balance consisting of nickel and unavoidable impurities.

Cobalt, chromium, tungsten, molybdenum and rhenium mainly participate in the hardening of the γ phase, the austenitic matrix of CFC structure.

Aluminum, titanium and tantalum favor the precipitation of the γ' phase, the hardening phase Ni ₃ (Al, Ti, Ta) of ordered cubic structure L1 ₂ .

Furthermore, rhenium makes it possible to slow down the diffusive processes, to limit the coalescence of the γ' phase, thus improving the resistance to creep at high temperature. However, the rhenium content should not be too high so as not to negatively impact the mechanical properties of the superalloy part.

The refractory elements of molybdenum, tungsten, rhenium and tantalum also help to slow diffusion-controlled mechanisms, thus improving the creep resistance of the superalloy part.

In addition, chromium and aluminum make it possible to improve resistance to oxidation and corrosion at high temperature, in particular around 900° C. for corrosion, and around 1100° C. for oxidaton.

The addition of silicon and hafnium also make it possible to optimize the resistance to hot oxidation of the superalloy by increasing the adhesion of the layer of alumina Al ₂ O ₃ which forms on the surface of the superalloy at high temperature by oxidizing medium.

Furthermore, chromium and cobalt make it possible to reduce the temperature of the solvus γ' of the superalloy.

Cobalt is an element chemically close to nickel which partly replaces nickel to form a solid solution in the γ phase, thus making it possible to reinforce the γ matrix, to reduce the sensitivity to precipitation of topologically compact phases, in particular the µ phases , P, R, and σ, and the phases of Lavas, and reduce susceptibility to secondary reaction zone (SRZ) formation.

Such a superalloy composition makes it possible to improve the mechanical strength properties at high temperature (650° C.-1200° C.) of parts made from said superalloy.

In particular, such a superalloy composition makes it possible to obtain a minimum breaking stress of 250MPa at 950°C for 1100h, as well as a minimum breaking stress of 150MPa at 1050°C for 550h, and as well as a minimum breaking stress of 55MPa at 1200°C for 510h.

Such mechanical properties are in particular due to a microstructure comprising a γ phase and a γ′ phase, and a maximum topologically compact phase content of 6%, in molar percentage. Topologically compact phases include the µ, P, R, and σ phases, as well as the Laves phases. The microstructure may also comprise the following carbides: MC, M ₆ C, M ₇ C ₃ , and M ₂₃ C ₆ .

Furthermore, these mechanical properties of resistance to temperature creep are obtained thanks to a better stability of the microstructure between 650°C and 1200°C.

Such a superalloy composition also makes it possible to improve the resistance to oxidation and corrosion of parts made from said superalloy. Corrosion and oxidation resistance is obtained by ensuring a minimum of 9.5%, in atomic percentage, of aluminum in the γ phase at 1200°C, and a minimum of 7.5%, in atomic percentage , of chromium in the γ phase at 1200°C, thus ensuring the formation of a protective layer of alumina on the surface of the material.

In addition, such a superalloy composition makes it possible to simplify the process for manufacturing the part. Such a simplification is ensured by obtaining a difference of at least 10° C. between the solvus temperature of the γ' precipitates and the solidus temperature of the superalloy, thus facilitating the implementation of a step for redissolving the γ precipitates ' during the manufacture of the part.

In addition, such a superalloy composition makes it possible to improve manufacture by reducing the risk of formation of defects during the manufacture of the part, and in particular the formation of parasitic grains of the "Freckles" type during directional solidification.

Indeed, the superalloy composition makes it possible to reduce the sensitivity of the part to the formation of parasitic “Freckles” grains. The sensitivity of the part to the formation of parasitic grains “Freckles” is evaluated using the Konter criterion, denoted NFP, which is given by the following equation (1):
[Math. 1] $$\mathit{NFP}=\frac{\left[\%\mathit{Your}+1.5\%\mathit{Off}+0.5\%\mathit{Mo}-0.5\%\mathit{You}\right]}{\left[\%W+1.2\%\mathit{D}\right]}$$

Where %Ta corresponds to the tantalum content in the superalloy, in mass percentage; where %Hf corresponds to the hafnium content in the superalloy, in mass percentage; where %Mo corresponds to the molybdenum content in the superalloy, in mass percentage; where %Ti corresponds to the titanium content in the superalloy, in mass percentage; where %W corresponds to the tungsten content in the superalloy, in mass percentage; and where %Re corresponds to the content of rhenium in the superalloy, in mass percentage.

The superalloy composition makes it possible to obtain an NFP parameter greater than or equal to 0.7, a value from which the formation of “Freckles” parasitic grains is greatly reduced.

Moreover, such a superalloy composition makes it possible to obtain a reduced density, in particular a density of less than 8.4 g/cm ³ .

Table 1 below gives the composition, in mass percentages, of seven examples of superalloys according to the invention, examples 1 to 11, as well as commercial or reference superalloys, examples 12 to 16. Example 12 corresponds to the René ^® N5 superalloy, Example 13 corresponds to the CMSX-4 ^® superalloy, Example 14 corresponds to the CMSX-4 Plus ^® Mod C superalloy, Example 15 corresponds to the René ^® N6 superalloy, and Example 16 corresponds CMSX-10 K ^® superalloy.

[Table 1]

Table 1 Alloys Neither Al Your You This CR Mo W D Off Others Ex 1 Balance 7 5 2 14 5 2 1 5 0 Ex 2 Balance 7 5 2 14 5 1 0 5 0 Ex 3 Balance 7 5 2 13 6 2 0 5 0 Ex 4 Balance 7 5 2 14 6 2 0 5 0 Ex 5 Balance 7 5 2 13 7 1 0 5 0 Ex 6 Balance 7 5 2 14 5 2 0 4 0 Ex 7 Balance 7 5 2 14 6 3 0 4 0 Ex 8 Balance 7 5 2 14 5 2 1 5 0.1 Ex 9 Balance 7 5 2 14 5 2 1 5 0.15 Ex 10 Balance 7 5 2 14 5 2 1 5 0 If 0.1 Ex 11 Balance 7 5 2 14 5 2 1 5 0.1 If 0.1 Ex 12 Balance 6.2 6 5 8 7 2 5 3 0.15 0.05C + 0.004B + 0.01Y Ex 1 3 Balance 5.6 6.5 1 9 6.5 0.6 6 3 0.1 Former 14 Balance 5.7 8 0.85 10 3.5 0.6 6 4.8 0.1 Ex 15 Balance 6 7.5 0 12.2 4.4 1.1 5.7 5.3 0.15 0.05C + 0.004B + 0.01Y Former 16 Balance 5.7 8 0.2 3 2 0.4 5 6 0.03 0.1 Nb + 0.01 Si

Table 2 gives estimated characteristics of the superalloys mentioned in table 1. The characteristics given in table 2 are the density (density), the Konter criterion (NFP), as well as the rupture stress by creep at 950° C in 1100h, the rupture stress by creep at 1050°C in 550h, and the rupture stress by creep at 1200°C in 510h, the rupture stresses by creep are named CRF in table 2.

[Table 2]

Table 2 Alloys Density NFP FRC
950°C/1100h (MPa) FRC
1050°C/550h (MPa) FRC
1200°C/510h (MPa) Ex 1 8.39 0.71 274 180 89 Ex 2 8.35 0.75 285 182 96 Ex 3 8.33 0.83 264 172 95 Ex 4 8.33 0.83 279 180 98 Ex 5 8.32 0.75 257 169 96 Ex 6 8.29 1.04 267 170 93 Ex 7 8.28 1.15 265 170 93 Ex 8 8.40 0.74 270 177 87 Ex 9 8.41 0.75 268 175 86 Ex 10 8.40 0.71 274 180 89 Ex 11 8.41 0.74 270 177 87 Ex 12 8.58 0.85 222 136 73 Ex 13 8.67 0.67 237 142 67 Former 14 8.90 0.68 265 150 56 Ex 15 8.87 0.69 278 158 66 Former 16 8.98 0.67 285 160 58

Table 3 gives estimated characteristics of the superalloys mentioned in table 1. The characteristics given in table 3 are the different transformation temperatures (the solvus, the solidus and the liquidus), the molar fraction of the γ' phase at 900° C, at 1050°C and at 1200°C, the molar fraction of the topologically compact phases (PTC) at 900°C and at 1050°C.

[Table 3]

Table 3 Transformation temperatures (°C) Molar fraction of γ' phase (%mol) Mole fraction of PTC (%mol) Alloys Solvus Solidus Liquidus 900°C 1050°C 1200°C 900°C 1050°C Ex 1 1281 1288 1376 81 70 40 3.9 0.4 Ex 2 1280 1303 1387 78 67 38 3.7 0 Ex 3 1280 1287 1373 80 68 39 4.8 0.1 Ex 4 1274 1286 1374 80 67 37 4.7 0 Ex 5 1275 1288 1374 77 65 35 4.3 0 Ex 6 1271 1291 1374 79 67 35 3.0 0 Ex 7 1271 1283 1367 82 68 36 5.3 0.2 Ex 8 1283 1280 1375 82 71 42 4.0 0.1 Ex 9 1282 1277 1375 82 71 42 4.0 0.2 Ex 10 1281 1285 1374 81 70 41 4.4 0.6 Ex 11 1281 1277 1373 82 71 41 4.5 0.7 Ex 12 1305 1335 1392 47 47 29 0 0 Ex 13 1269 1311 1385 45 45 23 0 0 Former 14 1307 1320 1398 53 52 34 0.4 0.5 Ex 15 1284 1336 1400 44 44 24 0.03 0.03 Former 16 1371 1382 1400 58 58 46 0.01 0.13

As illustrated in Table 3, for the superalloys of examples 1 to 11, the molar fractions of γ' phase are high at 1200° C. (between 35% and 40% in molar percentage), thus reflecting a high stability of the hardening precipitates, thereby improving the mechanical characteristics at high temperatures. In addition, the molar fraction of topologically compact phases for the superalloys of examples 1 to 11 is low at 900° C. (≈5%) and negligible at 1050° C. (<0.5%), also reflecting a high stability of the microstructure, which improves the mechanical characteristics at high temperatures.

Table 4 gives estimated characteristics of the superalloys mentioned in table 1. The characteristics given in table 4 are the activity of chromium in the γ phase at 900°C, and the activity of aluminum in the γ phase at 1100°C. THE activities of chromium and aluminum in the γ matrix are an indication of resistance to corrosion and oxidation, the higher the activity of chromium and the activity of aluminum in the matrix, the greater the resistance to corrosion and oxidation is high.

[Table 4]

Table 4 Cr activity in γ phase Al activity in γ phase Alloys 900°C 1100°C Ex 1 2.6E-3 1.94E-07 Ex 2 2.4 E-3 1.60E-07 Ex 3 3.0 E-3 1.96E-07 Ex 4 2.9 E-3 2.06E-07 Ex 5 3.4E-3 2.10E-07 Ex 6 3.0 E-3 1.89E-07 Ex 7 3.1E-3 2.07E-07 Ex 8 2.6E-3 1.95E-07 Ex 9 2.6E-3 1.96E-07 Ex 10 2.6E-3 2.05-07 Ex 11 2.6E-3 2.07-07 Ex 12 3.10E-3 1.29E-87 Ex 13 3.02E-3 1.27E-07 Former 14 1.50E-3 1.02E-07 Ex 15 1.79E-3 1.47E-07 Former 16 5.21E-4 4.23E-08

As illustrated in Tables 2, 3 and 4, the superalloys according to the invention have superior mechanical properties at high temperature to the alloys of the state of the art, while having a lower density and resistance to corrosion. superior corrosion and oxidation.

The properties given in tables 3 and 4 are estimated using the CALPHAD method (CALculation of PHAse Diagrams).

The nickel-based superalloy part can be made by foundry.

The casting of the part is made by melting the superalloy, the liquid superalloy being poured into a mold in order to be cooled and solidified. The manufacture by foundry of the part can for example be carried out with the lost wax technique, in particular to manufacture a blade.

Furthermore, in order to produce a single-crystal part, in particular a blade, the method may comprise a directed solidification step. Directed solidification is carried out by controlling the thermal gradient and the solidification rate of the superalloy, and by introducing a monocrystalline seed or by using a grain selector, in order to avoid the appearance of new seeds ahead of the solidification front.

Directed solidification can in particular allow the manufacture of a single-crystal blade whose crystalline structure is oriented along a crystallographic direction <001> which is parallel to the longitudinal direction of the blade, that is to say along the radial direction of the turbomachine, such an orientation offering better mechanical properties.

Claims (14)

1. A nickel-based superalloy comprising, in weight percent, 6 to 8% aluminum, 12 to 15% cobalt, 4 to 8% chromium, 0 to 0.2% hafnium, 0.5 to 4% molybdenum, 3.5 to 6% rhenium, 4 to 6% tantalum, 1 to 3% titanium, 0 to 2% tungsten, 0 to 0.1% silicon, the balance consisting of nickel and unavoidable impurities.
2. The superalloy as claimed in claim 1, wherein said superalloy comprises, in weight percent, 6 to 8% aluminum, 12 to 15% cobalt, 4 to 8% chromium, 0 to 0.2% hafnium, 0.5 to 4% molybdenum, 3.5 to 6% rhenium, 4 to 6% tantalum, 1 to 3% titanium, 0 to 2% tungsten, 0 to 0.05% silicon, the balance consisting of nickel and unavoidable impurities.
3. The superalloy as claimed in claim 1, wherein said superalloy comprises, in weight percent, 6 to 8% aluminum, 12 to 15% cobalt, 4 to 8% chromium, 0 to 0.15% hafnium, 0.5 to 4% molybdenum, 3.5 to 6% rhenium, 4 to 6% tantalum, 1 to 3% titanium, 0 to 2% tungsten, 0 to 0.1% silicon, the balance consisting of nickel and unavoidable impurities.
4. The superalloy as claimed in claim 1, wherein said superalloy comprises, in weight percent, 6.5 to 7.5% aluminum, 12 to 15% cobalt, 4.5 to 7.5% chromium, 0 to 0.2% hafnium, 0.5 to 3.5% molybdenum, 3.5 to 5.5% rhenium, 4.5 to 5.5% tantalum, 1.5 to 2.5% titanium, 0 to 1.5% tungsten, 0 to 0.1% silicon, the balance consisting of nickel and unavoidable impurities.
5. The superalloy as claimed in claim 4, wherein said superalloy comprises, in weight percent, 6.5 to 7.5% aluminum, 13 to 15% cobalt, 4.5 to 5.5% chromium, 0 to 0.2% hafnium 1.5 to 2.5% molybdenum, 4.5 to 5.5% rhenium, 4.5 to 5.5% tantalum, 1.5 to 2.5% titanium, 0.5 to 1.5% tungsten, the balance consisting of nickel and unavoidable impurities.
6. The superalloy as claimed in claim 4, wherein said superalloy comprises, in weight percent, 6.5 to 7.5% aluminum, 13 to 15% cobalt, 4.5 to 5.5% chromium, 0 to 0.2% hafnium, 0.5 to 1.5% molybdenum, 4.5 to 5.5% rhenium, 4.5 to 5.5% tantalum, 1.5 to 2.5% titanium, the balance consisting of nickel and unavoidable impurities.
7. The superalloy as claimed in claim 4, wherein said superalloy comprises, in weight percent, 6.5 to 7.5% aluminum, 12 to 14% cobalt, 5.5 to 6.5% chromium, 0 to 0.2% hafnium, 1.5 to 2.5% molybdenum, 4.5 to 5.5% rhenium, 4.5 to 5.5% tantalum, 1.5 to 2.5% titanium, the balance consisting of nickel and unavoidable impurities.
8. The superalloy as claimed in claim 4, wherein said superalloy comprises, in weight percent, 6.5 to 7.5% aluminum, 13 to 15% cobalt, 5.5 to 6.5% chromium, 0 to 0.2% hafnium, 1.5 to 2.5% molybdenum, 4.5 to 5.5% rhenium, 4.5 to 5.5% tantalum, 1.5 to 2.5% titanium, the balance consisting of nickel and unavoidable impurities.
9. The superalloy as claimed in claim 4, wherein said superalloy comprises, in weight percent, 6.5 to 7.5% aluminum, 12 to 14% cobalt, 6.5 to 7.5% chromium, 0 to 0.2% hafnium, 0.5 to 1.5% molybdenum, 4.5 to 5.5% rhenium, 4.5 to 5.5% tantalum, 1.5 to 2.5% titanium, the balance consisting of nickel and unavoidable impurities.
10. The superalloy as claimed in claim 4, wherein said superalloy comprises, in weight percent, 6.5 to 7.5% aluminum, 13 to 15% cobalt, 6.5 to 7.5% chromium, 0 to 0.2% hafnium, 1.5 to 2.5% molybdenum, 3.5 to 4.5% rhenium, 4.5 to 5.5% tantalum, 1.5 to 2.5% titanium, the balance consisting of nickel and unavoidable impurities.
11. The superalloy as claimed in claim 4, wherein said superalloy comprises, in weight percent, 6.5 to 7.5% aluminum, 13 to 15% cobalt, 5.5 to 6.5% chromium, 0 to 0.2% hafnium, 2.5 to 3.5% molybdenum, 3.5 to 4.5% rhenium, 4.5 to 5.5% tantalum, 1.5 to 2.5% titanium, the balance consisting of nickel and unavoidable impurities.
12. A nickel-based superalloy turbomachinery part as claimed in any one of claims 1 to 11.
13. The part as claimed in claim 12, wherein said part is single-crystal.
14. A process for manufacturing a nickel-based superalloy turbomachinery part as claimed in any one of claims 1 to 11 by casting.