EP3710611B1 - Nickel-based superalloy, single-crystal blade and turbomachine - Google Patents

Description

This presentation concerns nickel-based superalloys for gas turbines, in particular for the fixed blades, also called distributors or rectifiers, or mobile blades of a gas turbine, for example in the field of aeronautics.

It is known to use nickel-based superalloys for the manufacture of fixed or mobile monocrystalline blades of gas turbines for aircraft or helicopter engines. Gregori et al. shows for example. a nickel-based superalloy: CMSX-10 in “Welding in the World”, Springer, Vol. 51, No. 11/12, pages 34-47 .

The main advantages of these materials are that they combine both high creep resistance at high temperatures as well as resistance to oxidation and corrosion.

Over time, nickel-based superalloys for single-crystal blades have undergone significant changes in chemical composition, with the particular aim of improving their creep properties at high temperatures while maintaining resistance to the very aggressive environment in which these superalloys are used.

Furthermore, metallic coatings suitable for these alloys have been developed in order to increase their resistance to the aggressive environment in which these alloys are used, in particular resistance to oxidation and resistance to corrosion. Additionally, a ceramic coating of low thermal conductivity, performing a thermal barrier function, can be added to reduce the temperature on the metal surface.

Typically, a complete protection system has at least two layers.

The first layer, also called sub-layer or bonding layer, is directly deposited on the nickel-based superalloy part to be protected, also called substrate, for example a blade. The deposition step is followed by a diffusion step of the sublayer in the superalloy. Deposit and distribution can also be carried out in a single step.

The materials generally used to make this underlayer include aluminoforming metal alloys of the MCrAlY type (M = Ni (nickel) or Co (cobalt)) or a mixture of Ni and Co, Cr = chromium, Al = aluminum and Y = yttrium, or nickel aluminide type alloys (Ni _x Al _y ), some also containing platinum (Ni _x Al _y Pt _z ).

The second layer, generally called thermal barrier or "TBC" in accordance with the English acronym for "Thermal Barrier Coating", is a ceramic coating comprising for example yttriated zirconia, also called "YSZ" in accordance with the English acronym for " Yttria Stabilized Zirconia” or “YPSZ” in accordance with the English acronym for “Yttria Partially Stabilized Zirconia” and having a porous structure. This layer can be deposited by different processes, such as electron beam evaporation (“EB-PVD” in accordance with the English acronym for “Electron Beam Physical Vapor Deposition”), thermal spraying (“APS” in accordance with the English acronym for “Atmospheric Plasma Spraying” or “SPS” in accordance with the English acronym for “Suspension Plasma Spraying”), or any other process making it possible to obtain a porous ceramic coating with low thermal conductivity.

Due to the use of these materials at high temperatures, for example from 650°C to 1150°C, inter-diffusion phenomena occur on a microscopic scale between the nickel-based superalloy of the substrate and the metal alloy of the underlay. These inter-diffusion phenomena, associated with the oxidation of the undercoat, modify in particular the chemical composition, the microstructure and consequently the mechanical properties of the undercoat from the manufacture of the coating, then during the use of the coating. the blade in the turbine. These inter-diffusion phenomena also modify the chemical composition, the microstructure and consequently the mechanical properties of the superalloy of the substrate under the coating. In superalloys heavily loaded with refractory elements, particularly rhenium, a secondary reaction zone (ZRS) can thus form in the superalloy under the sub-layer to a depth of several tens, or even hundreds, of micrometers. The mechanical characteristics of this ZRS are significantly lower than those of the substrate superalloy. There ZRS formation is undesirable because it leads to a significant reduction in the mechanical strength of the superalloy.

These evolutions of the bonding layer, associated with the stress fields linked to the growth of the alumina layer which forms in service on the surface of this bonding layer, also called "TGO" in accordance with the English acronym for " Thermally Grown Oxide”, and differences in thermal expansion coefficients between the different layers, generate decohesion in the interfacial zone between the undercoat and the ceramic coating, which can lead to partial or total chipping of the ceramic coating. The metal part (superalloy substrate and metal underlayer) is then exposed and directly exposed to the combustion gases, which increases the risk of damage to the blade and therefore to the gas turbine.

In addition, the complexity of the chemistry of these alloys can lead to a destabilization of their optimal microstructure with the appearance of particles of undesirable phases when holding parts formed from these alloys at high temperatures. This destabilization has negative consequences on the mechanical properties of these alloys. These undesirable phases of complex crystal structure and fragile nature are called topologically compact phases (“PTC”) or “TCP” phases in accordance with the English acronym for “Topologically Close-Packed”.

In addition, foundry defects are likely to form in parts, such as blades, during their manufacture by directed solidification. These defects are generally parasitic grains of the “Freckle” type, the presence of which can cause premature failure of the part in service. The presence of these defects, linked to the chemical composition of the superalloy, generally leads to the rejection of the part, which results in an increase in production costs.

Object and summary of the invention

This presentation aims to propose nickel-based superalloy compositions for the manufacture of monocrystalline components, presenting increased performance in terms of lifespan and mechanical resistance and making it possible to reduce manufacturing costs. production of the part (reduction in scrap rate) compared to existing alloys. These superalloys have a higher temperature creep resistance than existing alloys while showing good microstructural stability in the volume of the superalloy (low sensitivity to the formation of PTC), good microstructural stability under the undercoat coating of the thermal barrier (low sensitivity to the formation of ZRS), good resistance to oxidation and corrosion while avoiding the formation of parasitic grains of the “Freckle” type.

For this purpose, the present presentation concerns a nickel-based superalloy comprising, in percentages by weight, 4.0 to 5.5% of rhenium, 3.5 to 12.5% of cobalt, 0.30 to 1.50%. molybdenum, 3.5 to 5.5% chromium, 3.5 to 5.5% tungsten, 4.5 to 6.0% aluminum, 0.35 to 1.50% titanium, 8, 0 to 10.5% tantalum, 0.15 to 0.30% hafnium, preferably 0.16 to 0.30% hafnium, preferably 0.17 to 0.30% hafnium, preferably 0. 18 to 0.30% hafnium, even more preferably 0.20 to 0.30% hafnium, 0.05 to 0.15% silicon, preferably 0.08 to 0.12% silicon, even more preferably 0.10% silicon, the remainder consisting of nickel and inevitable impurities.

This superalloy is intended for the manufacture of monocrystalline gas turbine components, such as fixed or moving blades.

Thanks to this composition of the nickel (Ni)-based superalloy, creep resistance is improved compared to existing superalloys, in particular at temperatures of up to 1200°C.

This alloy therefore has improved resistance to creep at high temperatures. This alloy also exhibits improved corrosion and oxidation resistance.

These superalloys have a density less than or equal to 9.00 g/cm ³ (gram per cubic centimeter).

A single-crystal part made of nickel-based superalloy is obtained by a directed solidification process under thermal gradient in lost wax foundry. The nickel-based monocrystalline superalloy comprises an austenitic matrix with a face-centered cubic structure, a nickel-based solid solution, called the gamma ("γ") phase. This matrix contains gamma prime hardening phase precipitates (“γ'”) of ordered cubic structure L1 ₂ of Ni ₃ Al type. The whole (matrix and precipitates) is therefore described as a γ/γ' superalloy.

Furthermore, this composition of the nickel-based superalloy allows the implementation of a heat treatment which puts into solution the γ' phase precipitates and the γ/γ' eutectic phases which form during the solidification of the superalloy. It is thus possible to obtain a single-crystal nickel-based superalloy containing γ' precipitates of controlled size, preferably between 300 and 500 nanometers (nm), and containing a small proportion of γ/γ' eutectic phases.

The heat treatment also makes it possible to control the volume fraction of the γ' phase precipitates present in the single-crystal nickel-based superalloy. The volume percentage of the γ' phase precipitates may be greater than or equal to 50%, preferably greater than or equal to 60%, even more preferably equal to 70%.

The major addition elements are cobalt (Co), chromium (Cr), molybdenum (Mo), rhenium (Re), tungsten (W), aluminum (AI), titanium (Ti) and tantalum (Ta).

The minor addition elements are hafnium (Hf) and silicon (Si), for which the maximum mass content is less than 1% by mass.

Among the unavoidable impurities, we can cite sulfur (S), carbon (C), boron (B), yttrium (Y), lanthanum (La) and cerium (Ce). Unavoidable impurities are defined as those elements which are not intentionally added to the composition and which are brought with other elements.

The addition of tungsten, chromium, cobalt, rhenium or molybdenum mainly makes it possible to reinforce the γ austenitic matrix with a face-centered cubic (fcc) crystal structure by hardening in solid solution.

The addition of aluminum, titanium or tantalum (Ta) promotes the precipitation of the hardening phase γ'-Ni ₃ (Al, Ti, Ta).

Rhenium slows down the diffusion of chemical species within the superalloy and limits the coalescence of γ' phase precipitates during service at high temperatures, a phenomenon which leads to a reduction in mechanical strength. Rhenium thus makes it possible to improve the creep resistance at high temperature of the nickel-based superalloy. However, too high a concentration of rhenium can lead to the precipitation of PTC intermetallic phases, for example σ phase, P phase or µ phase, which have a negative effect on the mechanical properties of the superalloy. Too high a rhenium concentration can also cause the formation of a secondary reaction zone in the superalloy under the undercoat, which has a negative effect on the mechanical properties of the superalloy.

The simultaneous addition of silicon and hafnium makes it possible to improve the resistance to hot oxidation of nickel-based superalloys by increasing the adhesion of the alumina layer (Al ₂ O ₃ ) which forms on the surface superalloy at high temperature. This alumina layer forms a passivation layer on the surface of the nickel-based superalloy and a barrier to the diffusion of oxygen coming from the outside to the inside of the nickel-based superalloy. However, we can add hafnium without also adding silicon or conversely add silicon without also adding hafnium and still improve the hot oxidation resistance of the superalloy.

Furthermore, the addition of chromium or aluminum makes it possible to improve the resistance to oxidation and corrosion at high temperatures of the superalloy. In particular, chromium is essential for increasing the hot corrosion resistance of nickel-based superalloys. However, too high a chromium content tends to reduce the solvus temperature of the γ' phase of the nickel-based superalloy, that is to say the temperature above which the γ' phase is completely dissolved in the γ matrix, which is undesirable. Also, the chromium concentration is between 3.5 to 5.5% by mass in order to maintain a high solvus temperature of the γ' phase of the nickel-based superalloy, for example greater than or equal to 1250°C but also to avoid the formation of topologically compact phases in the γ matrix highly saturated with alloy elements such as rhenium, molybdenum or tungsten.

The addition of cobalt, which is an element close to nickel and which partially replaces nickel, forms a solid solution with nickel in the γ matrix. Cobalt strengthens the γ matrix, reduces sensitivity to PTC precipitation and ZRS formation in the superalloy under the protective coating. However, too high a cobalt content tends to reduce the solvus temperature of the γ' phase of the nickel-based superalloy, which is undesirable.

The addition of refractory elements, such as molybdenum, tungsten, rhenium or tantalum makes it possible to slow down the mechanisms controlling the creep of nickel-based superalloys and which depend on the diffusion of chemical elements in the superalloy.

A very low sulfur content in a nickel-based superalloy makes it possible to increase the resistance to oxidation and hot corrosion as well as the resistance to chipping of the thermal barrier. Thus, a low sulfur content, less than 2 ppm by mass (part per million by mass), or even ideally less than 0.5 ppm by mass, makes it possible to optimize these properties. Such a mass sulfur content can be obtained by producing a low-sulfur mother casting or by a desulfurization process carried out after the casting. It is notably possible to maintain a low sulfur level by adapting the superalloy production process.

By nickel-based superalloys we mean superalloys whose nickel mass percentage is the majority. We understand that nickel is therefore the element with the highest mass percentage in the alloy.

The superalloy may comprise, in mass percentages, 4.0 to 5.5% of rhenium, 3.5 to 8.5% of cobalt, 0.30 to 1.50% of molybdenum, 3.5 to 5.5% chromium, 3.5 to 4.5% tungsten, 4.5 to 6.0% aluminum, 0.50 to 1.50% titanium, 8.0 to 10.5% tantalum, 0. 15 to 0.30% hafnium, preferably 0.17 to 0.30% hafnium, even more preferably 0.20 to 0.30% hafnium, 0.05 to 0.15% silicon, the remainder being made up of nickel and inevitable impurities.

The superalloy may comprise, in mass percentages, 4.0 to 5.5% of rhenium, 3.5 to 12.5% of cobalt, 0.30 to 1.50% of molybdenum, 3.5 to 5.5% chromium, 3.5 to 5.5% tungsten, 5.0 to 6.0% aluminum, 0.35 to 1.50% titanium, 8.0 to 10.5% tantalum, 0. 15 to 0.30% hafnium, preferably 0.17 to 0.30% hafnium, even more preferably 0.20 to 0.30% hafnium, 0.05 to 0.15% silicon, the remainder consisting of nickel and inevitable impurities.

The superalloy may comprise, in mass percentages, 4.5 to 5.5% of rhenium, 4.0 to 6.0% of cobalt, 0.30 to 1.00% of molybdenum, 3.5 to 4.5% chromium, 3.5 to 4.5% tungsten, 4.5 to 6.0% aluminum, 0.50 to 1.50% titanium, 8.0 to 10.5% tantalum, 0. 15 to 0.30% hafnium, preferably 0.17 to 0.30% hafnium, even more preferably 0.20 to 0.30% hafnium, 0.05 to 0.15% silicon, the remainder being made up of nickel and inevitable impurities.

The superalloy may comprise, in mass percentages, 4.5 to 5.5% of rhenium, 3.5 to 12.5% of cobalt, 0.50 to 1.50% of molybdenum, 3.5 to 4.5% chromium, 3.5 to 4.5% tungsten, 5.0 to 6.0% aluminum, 0.50 to 1.50% titanium, 8.0 to 9.0% tantalum, 0. 15 to 0.30% hafnium, preferably 0.17 to 0.30% hafnium, even more preferably 0.20 to 0.30% hafnium, 0.05 to 0.15% silicon, the remainder being made up of nickel and inevitable impurities.

The superalloy may comprise, in mass percentages, 4.5 to 5.5% of rhenium, 7.0 to 9.0% of cobalt, 0.50 to 1.50% of molybdenum, 3.5 to 4.5% chromium, 3.5 to 4.5% tungsten, 5.0 to 6.0% aluminum, 0.50 to 1.50% titanium, 8.0 to 9.0% tantalum, 0. 15 to 0.30% hafnium, preferably 0.17 to 0.30% hafnium, even more preferably 0.20 to 0.30% hafnium, 0.05 to 0.15% silicon, the remainder being made up of nickel and inevitable impurities.

The superalloy may comprise, in mass percentages, 4.2 to 5.3% of rhenium, 6.0 to 8.0% of cobalt, 0.30 to 1.00% of molybdenum, 3.5 to 4.5% chromium, 4.5 to 5.5% tungsten, 5.0 to 6.0% aluminum, 0.35 to 1.30% titanium, 8.0 to 9.0% tantalum, 0. 15 to 0.30% hafnium, preferably 0.17 to 0.30% hafnium, even more preferably 0.20 to 0.30% hafnium, 0.05 to 0.15% silicon, the remainder being made up of nickel and possible impurities.

The superalloy may comprise, in mass percentages, 4.0 to 5.0% rhenium, 4.0 to 6.0% cobalt, 0.30 to 1.00% molybdenum, 4.5 to 5.5% chromium, 3.5 to 4.5% tungsten, 5.0 to 6.0% aluminum, 0.35 to 1.30% titanium, 8.0 to 10.5% tantalum, 0. 15 to 0.30% hafnium, preferably 0.17 to 0.30% hafnium, even more preferably 0.20 to 0.30% hafnium, 0.05 to 0.15% silicon, the remainder consisting of nickel and inevitable impurities.

The superalloy may comprise, in percentages by weight, 5.2% of rhenium, 5.0% of cobalt, 0.50% of molybdenum, 4.0% of chromium, 4.0% of tungsten, 5.4% of aluminum, 1.00% titanium, 8.5% tantalum, 0.25% hafnium, 0.10% silicon, the remainder consisting of nickel and unavoidable impurities.

The superalloy may comprise, in percentages by weight, 5.2% of rhenium, 5.0% of cobalt, 0.50% of molybdenum, 4.0% of chromium, 4.0% of tungsten, 5.4% of aluminum, 1.00% titanium, 8.5% tantalum, 0.17% hafnium, 0.10% silicon, the remainder consisting of nickel and unavoidable impurities.

The superalloy may comprise, in percentages by weight, 5.2% of rhenium, 5.0% of cobalt, 0.50% of molybdenum, 4.0% of chromium, 4.0% of tungsten, 5.1% of aluminum, 1.00% titanium, 10.0% tantalum, 0.25% hafnium, 0.10% silicon, the remainder consisting of nickel and unavoidable impurities.

The superalloy may comprise, in percentages by weight, 5.0% rhenium, 12.0% cobalt, 1.00% molybdenum, 4.0% chromium, 4.0% tungsten, 5.4% aluminum, 1.00% titanium, 8.5% tantalum, 0.25% hafnium, 0.10% silicon, the remainder consisting of nickel and unavoidable impurities.

The superalloy may comprise, in percentages by weight, 5.0% rhenium, 4.0% cobalt, 1.00% molybdenum, 4.0% chromium, 4.0% tungsten, 5.4% aluminum, 1.00% titanium, 8.5% tantalum, 0.25% hafnium, 0.10% silicon, the remainder consisting of nickel and unavoidable impurities.

The superalloy may comprise, in percentages by weight, 4.9% of rhenium, 8.0% of cobalt, 1.00% of molybdenum, 4.2% of chromium, 4.0% of tungsten, 5.4% of aluminum, 1.00% titanium, 8.5% tantalum, 0.25% hafnium, 0.10% silicon, the remainder consisting of nickel and unavoidable impurities.

The superalloy may comprise, in percentages by weight, 4.9% of rhenium, 8.0% of cobalt, 1.00% of molybdenum, 4.2% of chromium, 4.0% of tungsten, 5.4% of aluminum, 1.00% titanium, 8.5% tantalum, 0.17% hafnium, 0.10% silicon, the remainder consisting of nickel and inevitable impurities.

The superalloy may comprise, in percentages by weight, 4.9% of rhenium, 8.0% of cobalt, 1.00% of molybdenum, 4.2% of chromium, 4.0% of tungsten, 5.4% of aluminum, 1.00% titanium, 8.5% tantalum, 0.16% hafnium, 0.10% silicon, the remainder consisting of nickel and unavoidable impurities.

The superalloy may comprise, in percentages by weight, 4.7% of rhenium, 7.0% of cobalt, 0.50% of molybdenum, 4.0% of chromium, 5.0% of tungsten, 5.4% of aluminum, 0.80% titanium, 8.5% tantalum, 0.25% hafnium, 0.10% silicon, the remainder consisting of nickel and unavoidable impurities.

The superalloy may comprise, in percentages by weight, 4.5% of rhenium, 5.0% of cobalt, 0.50% of molybdenum, 5.0% of chromium, 4.0% of tungsten, 5.4% of aluminum, 1.00% titanium, 8.5% tantalum, 0.25% hafnium, 0.10% silicon, the remainder consisting of nickel and unavoidable impurities.

The superalloy may comprise, in percentages by weight, 4.5% of rhenium, 5.0% of cobalt, 0.50% of molybdenum, 5.0% of chromium, 4.0% of tungsten, 5.4% of aluminum, 0.55% titanium, 10.0% tantalum, 0.25% hafnium, 0.10% silicon, the remainder consisting of nickel and unavoidable impurities.

The superalloy may comprise, in percentages by weight, 4.3% of rhenium, 5.0% of cobalt, 0.50% of molybdenum, 4.0% of chromium, 4.0% of tungsten, 5.4% of aluminum, 1.00% titanium, 8.5% tantalum, 0.25% hafnium, 0.10% silicon, the remainder consisting of nickel and unavoidable impurities.

The present presentation also relates to a single-crystal blade for a turbomachine comprising a superalloy as defined above.

This blade therefore has improved resistance to creep at high temperatures.

The blade may comprise a protective coating comprising a metallic underlayer deposited on the superalloy and a ceramic thermal barrier deposited on the metallic underlayer.

Thanks to the composition of the nickel-based superalloy, the formation of a secondary reaction zone in the superalloy resulting from inter-diffusion phenomena between the superalloy and the sub-layer is avoided, or limited.

The metallic underlayer can be an MCrAlY type alloy or a nickel aluminide type alloy.

The ceramic thermal barrier can be a material based on yttriated zirconia or any other ceramic coating (based on zirconia) with low thermal conductivity.

The blade may have a structure oriented in a crystallographic direction <001>.

This orientation generally gives optimal mechanical properties to the blade.

This presentation also concerns a turbomachine comprising a blade as defined above.

Brief description of the drawings

• la figure 1 est une vue schématique en coupe longitudinale d'une turbomachine ;
• la figure 2 est un graphique représentant le paramètre NFP (No-Freckles Parameter) pour différents superalliages ;
• la figure 3 est un graphique représentant la fraction volumique de phase γ' à différentes températures et pour différents superalliages.

Other characteristics and advantages of the invention will emerge from the following description of embodiments of the invention, given by way of non-limiting examples, with reference to the single appended figure, in which:

• there figure 1 is a schematic view in longitudinal section of a turbomachine;
• there figure 2 is a graph representing the No-Freckles Parameter (NFP) for different superalloys;
• there Figure 3 is a graph representing the phase volume fraction γ' at different temperatures and for different superalloys.

Detailed description of the invention

Nickel-based superalloys are intended for the manufacture of single-crystal blades by a directed solidification process in a thermal gradient. The use of a single crystal seed or a grain selector at the start of solidification makes it possible to obtain this single crystal structure. The structure is oriented for example in a crystallographic direction <001> which is the orientation which generally confers optimal mechanical properties to superalloys.

The raw solidified single-crystal nickel-based superalloys have a dendritic structure and are made up of γ' Ni ₃ (Al, Ti, Ta) precipitates dispersed in a γ matrix of face-centered cubic structure, solid solution based on nickel. These γ' phase precipitates are distributed heterogeneously in the volume of the single crystal due to chemical segregations resulting from the solidification process. Furthermore, γ/γ' eutectic phases are present in the inter-dendritic regions and constitute preferential crack initiation sites. These γ/γ' eutectic phases form at the end of solidification. In addition, the γ/γ' eutectic phases are formed to the detriment of the fine precipitates (size less than a micrometer) of the γ' hardening phase. These γ' phase precipitates constitute the main source of hardening of nickel-based superalloys. Also, the presence of residual γ/γ' eutectic phases does not make it possible to optimize the hot creep resistance of the nickel-based superalloy.

It has in fact been shown that the mechanical properties of superalloys, in particular creep resistance, were optimal when the precipitation of the γ' precipitates was ordered, that is to say that the γ' phase precipitates are aligned in such a way. regular, with a size ranging from 300 to 500 nm, and when all of the γ/γ' eutectic phases were put back into solution.

The raw solidified nickel-based superalloys are therefore heat treated to obtain the desired distribution of the different phases. The first heat treatment is a microstructure homogenization treatment which aims to dissolve the γ' phase precipitates and to eliminate the γ/γ' eutectic phases or to significantly reduce their volume fraction. This treatment is carried out at a temperature higher than the solvus temperature of the γ' phase and lower than the starting melting temperature of the superalloy (T _solidus ). Quenching is then carried out at the end of this first heat treatment to obtain a fine and homogeneous dispersion of the γ' precipitates. Tempering heat treatments are then carried out in two stages, at temperatures lower than the solvus temperature of the γ' phase. During a first step, to increase the size of the γ' precipitates and obtain the desired size, then during a second step, to increase the volume fraction of this phase to approximately 70% at room temperature.

There figure 1 represents, in section along a vertical plane passing through its main axis A, a dual-flow turbojet 10. The dual-flow turbojet 10 comprises, from upstream to downstream according to the circulation of the air flow, a fan 12, a compressor low pressure 14, a high pressure compressor 16, a combustion chamber 18, a high pressure turbine 20, and a low pressure turbine 22.

The high pressure turbine 20 comprises a plurality of moving blades 20A rotating with the rotor and rectifiers 20B (fixed blades) mounted on the stator. The stator of the turbine 20 comprises a plurality of stator rings 24 arranged opposite the moving blades 20A of the turbine 20.

These properties make these superalloys interesting candidates for the manufacture of monocrystalline parts intended for the hot parts of turbojet engines.

It is therefore possible to manufacture a moving blade 20A or a rectifier 20B for a turbomachine comprising a superalloy as defined above.

It is also possible to manufacture a moving blade 20A or a rectifier 20B for a turbomachine comprising a superalloy as defined previously coated with a protective coating comprising a metallic underlayer
A turbomachine can in particular be a turbojet such as a double-flow turbojet 10. The turbomachine can also be a single-flow turbojet, a turboprop or a turboshaft engine.

Examples

Ten nickel-based monocrystalline superalloys of this presentation (Ex 1 to Ex 10) were studied and compared to four commercial monocrystalline superalloys CMSX-4 (Ex 11), CMSX-4PlusC (Ex 12), CMSX-10 (Ex 13) and René N6 (Ex 14). The chemical composition of each of the single-crystal superalloys is given in Table 1, the composition Ex 13 additionally comprising 0.10% by mass of niobium (Nb) and the composition Ex 14 further comprising 0.05% by mass of carbon (C) and 0.004% by mass of boron (B). All of these superalloys are nickel-based superalloys, that is to say that the 100% complement of the compositions presented consists of nickel and unavoidable impurities. Table 1 D Co MB Cr W HAVE Ti Your Hf If Ex 1 5.2 5.0 0.50 4.0 4.0 5.4 1.00 8.5 0.25 0.10 Ex 2 5.2 5.0 0.50 4.0 4.0 5.1 1.00 10.0 0.25 0.10 Ex 3 5.0 12.0 1.00 4.0 4.0 5.4 1.00 8.5 0.25 0.10 Ex 4 5.0 4.0 1.00 4.0 4.0 5.4 1.00 8.5 0.25 0.10 Ex 5 4.9 8.0 1.00 4.2 4.0 5.4 1.00 8.5 0.25 0.10 EX 6 4.9 8.0 1.00 4.2 4.0 5.4 1.00 8.5 0.16 0.10 Ex 7 4.7 7.0 0.50 4.0 5.0 5.4 0.80 8.5 0.25 0.10 Ex 8 4.5 5.0 0.50 5.0 4.0 5.4 1.00 8.5 0.25 0.10 Ex 9 4.5 5.0 0.50 5.0 4.0 5.4 0.55 10.0 0.25 0.10 Ex 10 4.3 5.0 0.50 4.0 4.0 5.4 1.00 8.5 0.25 0.10 Ex 11 3.0 9.6 0.60 6.5 6.4 5.6 1.00 6.5 0.10 0.00 Ex 12 4.8 10.0 0.60 3.5 6.0 5.7 0.85 8.0 0.10 0.00 Ex 13 6.0 3.0 0.40 2.0 5.0 5.7 0.20 8.0 0.03 0.00 Ex 14 5.3 12.2 1.10 4.4 5.7 6.0 0.00 7.5 0.15 0.00

Volumic mass

1. (1) D = 27,68 x [D₁ + 0,14037 - 0,00137 %Cr - 0,00139 %Ni - 0,00142 %Co - 0,00140 %Fe - 0,00186 %Mo - 0,00125 %W - 0,00134 %V - 0,00119 %Nb - 0,00113 %Ta + 0,0004 %Ti + 0,00388 %C + 0,0000187 (%Mo)² - 0,0000506 (%Co)x(%Ti) - 0,00096 %Re - 0,001131 %Ru]
   où
   $${\mathrm{D}}_1=100/\left[\left(\mathrm{\%Cr}/{\mathrm{D}}_{\mathrm{Cr}}\right)+\left(\mathrm{\%Ni}/{\mathrm{D}}_{\mathrm{Ni}}\right)+\dots +\left(\mathrm{\%X}/{\mathrm{D}}_{\mathrm{X}}\right)\right]$$
   
   • où D_Cr, D_Ni,..., D_X sont les masses volumiques des éléments Cr, Ni, ..., X exprimées en lb/in³ (livre par pouce cube) et D est la masse volumique du superalliage exprimé en g/cm³.
   • où %Cr, %Ni, ...%X sont les teneurs, exprimées en pourcentages massiques, des éléments du superalliage Cr, Ni, ..., X.

The room temperature density of each superalloy was estimated using a modified version of the Hull formula (FC Hull, Metai Progress, November 1969, pp139-140). This empirical equation was proposed by Hull. The empirical equation is based on the law of mixtures and includes corrective terms deduced from a linear regression analysis of experimental data (chemical compositions and measured densities) concerning 235 superalloys and stainless steels. This Hull formula has been modified, in particular to take into account elements such as rhenium and ruthenium. The modified Hull formula is as follows:

1. (1) D = 27.68 x [D ₁ + 0.14037 - 0.00137 %Cr - 0.00139 %Ni - 0.00142 %Co - 0.00140 %Fe - 0.00186 %Mo - 0.00125 %W - 0.00134 %V - 0.00119 %Nb - 0.00113 %Ta + 0.0004 %Ti + 0.00388 %C + 0.0000187 (%Mo) ² - 0.0000506 (%Co)x(%Ti) - 0.00096 %Re - 0.001131 %Ru]
   Or
   $${\mathrm{D}}_1=100/\left[\left(\mathrm{\%Cr}/{\mathrm{D}}_{\mathrm{Cr}}\right)+\left(\mathrm{\%Neither}/{\mathrm{D}}_{\mathrm{Neither}}\right)+\dots +\left(\mathrm{\%X}/{\mathrm{D}}_{\mathrm{X}}\right)\right]$$
   
   • where D _Cr , D _Ni ,..., D _X are the density of the elements Cr, Ni, ^... , g/cm ³ .
   • where %Cr, %Ni, ...%X are the contents, expressed in mass percentages, of the elements of the superalloy Cr, Ni, ..., X.

The densities calculated for the alloys of the invention and for the reference alloys are less than 9.00 g/cm ³ (see Table 2).

The comparison between the estimated and measured densities (see table 2) makes it possible to validate the modified Hull model (equation (1)). The estimated and measured densities are consistent.

Table 2 presents different parameters for superalloys Ex 1 to Ex 14. Table 2 Estimated density (1) (g/cm ³ ) Measured density (g/cm ³ ) NFP RGP M d [ZRS(%)] ^1/2 Ex 1 8.89 8.82 0.84 0.393 0.98 5.3 Ex 2 9.00 8.98 0.99 0.460 0.98 5.2 Ex 3 8.86 - 0.89 0.393 0.99 1.0 Ex 4 8.88 - 0.89 0.393 0.98 3.8 Ex 5 8.86 8.86 0.90 0.393 0.98 3.4 Ex 6 - - 0.88 0.393 - 3.4 Ex 7 8.91 - 0.82 0.386 0.98 3.6 Ex 8 8.83 8.79 0.92 0.393 0.98 -5.9 Ex 9 8.91 - 1.10 0.388 0.98 -6.5 Ex 10 - - 0.94 0.393 - 3.4 Ex 11 8.71 - 0.65 0.358 0.99 -24 Ex 12 8.91 - 0.68 0.371 0.99 8.5 Ex 13 8.99 - 0.67 0.299 0.96 28 Ex 14 8.87 - 0.69 0.256 0.98 1.1

No-Freckles Parameter (NFP)

où %Cr, %Ni, ...%X sont les teneurs, exprimées en pourcentages massiques, des éléments du superalliage Cr, Ni, ..., X. $$\mathrm{NFP}=\left[\mathrm{\%Your}+1.5\mathrm{\%Hf}+0.5\mathrm{\%MB}-0.5\mathrm{\%}\mathrm{\%Ti})\right]/\left[\begin{array}{l}\mathrm{\%W}+1.2\\ \mathrm{\%D}\end{array})\right]$$

where %Cr, %Ni, ...%X are the contents, expressed in mass percentages, of the elements of the superalloy Cr, Ni, ..., X.

The NFP parameter makes it possible to quantify the sensitivity to the formation of parasitic grains of the “Freckles” type during the directed solidification of the part (document US 5,888,451 ). To avoid the formation of “Freckles” type defects, the NFP parameter must be greater than or equal to 0.7.

As can be seen in Table 2 and on the figure 2 , superalloys Ex 1 to Ex 10 all have an NFP parameter greater than or equal to 0.7 while commercial superalloys Ex 11 to Ex 14 have an NFP parameter less than 0.7.

Resistance Gamma Prime (RGP)

où C_Ti, C_Ta, Cw et C_Al sont les concentrations, exprimées en pourcentage atomique, respectives des éléments Ti, Ta, W et AI dans le superalliage.The intrinsic mechanical resistance of the γ' phase increases with the content of elements replacing aluminum in the Ni ₃ Al compound, such as titanium, tantalum and part of the tungsten. The phase compound γ' can therefore be written as Ni ₃ (Al, Ti, Ta, W). The RGP parameter makes it possible to estimate the level of hardening of the γ' phase: $$\mathrm{RGP}=\left[{\mathrm{VS}}_{\mathrm{Ti}}+{\mathrm{VS}}_{\mathrm{Your}}+\left({\mathrm{VS}}_{\mathrm{W}}/2\right)\right]/{\mathrm{VS}}_{\mathrm{Al}}$$

where C _Ti , C _Ta , Cw and C _Al are the respective concentrations, expressed in atomic percentage, of the elements Ti, Ta, W and AI in the superalloy.

A higher RGP parameter is favorable to better mechanical strength of the superalloy. It can be seen in Table 2 that the RGP parameter calculated for superalloys Ex 1 to Ex 10 is greater than the RGP parameter calculated for commercial superalloys Ex 11 to Ex 14.

Sensitivity to PTC formation ( M d )

où X_i est la fraction de l'élément i dans le superalliage exprimée en pourcentage atomique, (Md)_i est la valeur du paramètre Md pour l'élément i.The parameter M d is defined as follows: $$\bar{M}d={\displaystyle {\sum }_{i=1}^{\mathrm{not}}{X}_i{\left(\mathit{MD}\right)}_i}$$

where X _i is the fraction of element i in the superalloy expressed as an atomic percentage, (Md) _i is the value of the parameter Md for element i.

Table 3 presents the Md values for the different elements of the superalloys. Table 3 Element MD Element MD Ti 2,271 Hf 3.02 Cr 1,142 Your 2,224 Co 0.777 W 1,655 Neither 0.717 D 1,267 No. 2,117 HAVE 1.9 MB 1.55 If 1.9 Ru 1.006

Sensitivity to PTC formation is determined by the parameter M d, according to the New PHACOMP method which was developed by Morinaga et al. ( Morinaga et al., New PHACOMP and its application to alloy design, Superalloys 1984, edited by M Gell et al., The Metallurgical Society of AIME, Warrendale, PA, USA (1984) pp. 523-532 ). According to this model, the sensitivity of superalloys to PTC formation increases with the value of the parameter M d.

As can be seen in Table 2, the superalloys Ex 1 to Ex 14 present values of the parameter M d substantially equal. These superalloys therefore have similar sensitivities to the formation of PTC, sensitivities which are relatively low.

Sensitivity to ZRS formation

où ZRS(%) est le pourcentage linéique de ZRS dans le superalliage sous le revêtement et où les concentrations des éléments d'alliage sont en pourcentages atomiques.To estimate the sensitivity of nickel-based superalloys containing rhenium to the formation of ZRS, Walston (document US 5,270,123 ) established the following equation: $$\begin{array}{l}{\left[\mathrm{ZRS}\left(\mathrm{\%}\right)\right]}^{1/2}=13.88\left(\mathrm{\%D}\right)+4.10\left(\mathrm{\%W}\right)-7.07\left(\mathrm{\%Cr}\right)-2.94\\ \left(\mathrm{\%MB}\right)-0.33\left(\mathrm{\%Co}\right)+12.13\end{array}$$

where ZRS(%) is the linear percentage of ZRS in the superalloy under the coating and where the concentrations of the alloying elements are in atomic percentages.

This equation (5) was obtained by multiple linear regression analysis from observations made after aging for 400 hours at 1093°C (degree centigrade) of samples of various alloys with compositions close to the Ex 12 composition under a coating NiPtAI.

The higher the value of the parameter [ZRS(%)] ^1/2 , the more sensitive the superalloy is to the formation of ZRS. Thus, as can be seen in Table 2, for superalloys Ex 1 to Ex 10, the values of the parameter [ZRS(%)] ^1/2 are either negative or weakly positive and these superalloys therefore have low sensitivity to the formation of ZRS under a NitPtAl coating, much like the commercial superalloy Ex 14 which is known for its low susceptibility to the formation of ZRS. For example, the commercial superalloy EX 13, which is known to be very sensitive to the formation of ZRS under a NiPtAl coating, has a relatively high value of the parameter [ZRS(%)] ^1/2 .

Solvus temperature of the γ' phase

The ThermoCalc software (Ni25 database) based on the CALPHAD method was used to calculate the solvus temperature of the γ' phase at equilibrium.

As can be seen in Table 4, superalloys Ex 1 to Ex 10 have a solvus temperature γ' higher than the solvus temperature γ' of superalloys Ex 11, Ex 12 and Ex 14.

Volume fraction of phase y'

The ThermoCalc software (Ni25 database) based on the CALPHAD method was used to calculate the volume fraction (in volume percentage) of γ' phase at equilibrium in the superalloys Ex 1 to Ex 14 at 950°C, 1050° C and 1200°C.

As can be seen in Table 4 and on the Figure 3 , superalloys Ex 1 to Ex 10 contain γ' phase volume fractions greater than or comparable to the γ' phase volume fractions of commercial superalloys Ex 11 to Ex 14.

Thus, the combination of a high γ' solvus temperature and high γ' phase volume fractions for superalloys Ex 1 to Ex 10 is favorable for good creep resistance at high temperatures and very high temperatures, for example at 1200 °C. This resistance must therefore be greater than the creep resistance of superalloys. commercial Ex 11 to Ex 14 and close to that of the commercial superalloy Ex 13. Table 4 T _solvus γ' (°C) Phase volume fraction γ' (% vol) 950°C 1050°C 1200°C Ex 1 1347 64 59 44 Ex 2 1353 66 61 47 Ex 3 1280 67 62 44 Ex 4 1346 68 63 47 Ex 5 1328 61 55 38 Ex 6 1314 64 57 36 Ex 7 1328 64 58 38 Ex 8 1342 63 58 43 Ex 9 1347 65 60 46 Ex 10 1336 66 61 43 Ex 11 1290 58 48 25 Ex 12 1320 63 57 36 Ex 13 1374 65 60 46 Ex 14 1283 60 51 24

Volume fraction of σ type PTC

The ThermoCalc software (Ni25 database) based on the CALPHAD method was used to calculate the volume fraction (in volume percentage) of phase σ at equilibrium in the superalloys Ex 1 to Ex 14 at 950°C and 1050°C (see table 5).

The calculated σ phase volume fractions are relatively low, reflecting low sensitivity to PTC precipitation. These results therefore corroborate the results obtained with the New PHACOMP method (parameter M d).

Mass concentration of chromium dissolved in the γ matrix

The ThermoCalc software (Ni25 database) based on the CALPHAD method was used to calculate chromium content (in mass percentage) in the γ phase at equilibrium in superalloys Ex 1 to Ex 14 at 950°C, 1050° C and 1200°C.

As can be seen in Table 5, the chromium concentrations in the γ phase are higher for the superalloys Ex 1 to Ex 10, compared to the chromium concentrations in the γ phase for commercial superalloys Ex 12 to Ex 14, which is favorable for better resistance to corrosion and hot oxidation. Table 5 Volume fraction of σ type PTC (in % vol) Chromium content in the γ phase (in % by mass) 950°C 1050°C 950°C 1050°C 1200°C Ex 1 1.1 0.5 8.63 7.65 5.79 Ex 2 1.4 0.7 9.02 8.03 6.25 Ex 3 1.2 0.6 8.63 7.64 5.79 Ex 4 1.4 0.7 8.77 7.82 5.96 Ex 5 1.2 0.1 8.86 7.81 6.05 Ex 6 0.9 0.1 11.00 9.50 6.80 Ex 7 0.8 0.6 8.35 7.30 5.45 Ex 8 0.9 0.2 10.83 9.63 7.57 Ex 9 1.2 0.5 11.25 9.95 7.71 Ex 10 0.4 0.0 10.40 9.20 6.80 Ex 11 0.7 - 12.80 10.90 7.84 Ex 12 1.2 0.5 7.40 6.43 4.82 Ex 13 0.9 0.4 3.62 3.36 2.77 Ex 14 1.0 0.3 8.37 7.10 5.25

Creep property at very high temperature

Creep tests were carried out on superalloys Ex 2, Ex 5, Ex 6, Ex 11, Ex 13 and Ex 14. The creep tests are carried out at 1200°C and 80 MPa according to standard NF EN ISO 204 of August 2009 (Guide U125_J).

Table 6 presents the results of the creep tests in which the superalloys were placed under load (80 MPa) at 1200°C. The results represent the time in hours (h) at the rupture of the test piece. Table 6 Breaking time (hour) Ex 2 41 Ex 5 65 Ex 6 50 Ex 10 54 Ex 11 9 Ex 13 59 Ex 14 13

The Ex 2, Ex 5, Ex 6 and Ex 10 superalloys exhibit better creep behavior than the Ex 11 and Ex 14 alloys. The Ex 13 superalloy also exhibits good creep properties.

Cyclic oxidation property at 1150°C

The superalloys are subjected to one of the thermal cycles as described in INS-TTH-001 and INS-TTH-002: Oxidative cycling test method (Mass loss test and Thermal barrier).

A specimen of the superalloy tested (pin having a diameter of 20 mm and a height of 1 mm) is subjected to a thermal cycle, each cycle of which includes a rise to 1150°C in less than 15 min (minutes), a plateau at 1150° C of 60 min and turbine cooling of the test piece for 15 min.

The thermal cycle is repeated until a loss in mass of the test piece equal to 20 mg/cm ² (milligrams per square centimeter) is observed.

The lifespan of the tested superalloys is presented in Table 7. Table 7 Lifespan (hours) Ex 2 1310 Ex 5 > 1700 Ex 10 > 1700 Ex 11 ~230 Ex 12 ~480 Ex 13 ~100

It can be seen that the Ex 2, Ex 5 and Ex 10 superalloys have a much longer lifespan than the superalloys. Ex 11, Ex 12 and Ex 13. Note that the oxidation properties of the Ex 13 superalloy are much worse than those of the Ex 2, Ex 5 and Ex 10 superalloys.

Microstructural stability

After aging for 300 hours at 1050°C, no PTC phase is observed for the Ex 6 superalloy by scanning electron microscopy image analysis.

Susceptibility to the formation of foundry defects

After forming by a lost wax type process and directed solidification in a Bidgman furnace, no defects resulting from the foundry process, in particular of the "Freckles" type, were observed in the superalloys Ex 2, Ex 5, Ex 6 and Ex 10. “Freckels” type defects are observed after immersion of the test piece in a solution based on HNO ₃ /H ₂ SO ₄ .

Although the present disclosure has been described with reference to a specific embodiment, it is obvious that various modifications and changes can be made to these examples without departing from the general scope of the invention as defined by the claims. Furthermore, individual features of the different embodiments discussed may be combined in additional embodiments. Therefore, the description and drawings should be considered in an illustrative rather than a restrictive sense.

Claims (24)

1. A nickel-based superalloy comprising, in percentages by mass, 4.0 to 5.5% rhenium, 3.5 to 12.5% cobalt, 0.30 to 1.50% molybdenum, 3.5 to 5.5% chromium, 3.5 to 5.5% tungsten, 4.5 to 6.0% aluminum, 0.35 to 1.50% titanium, 8.0 to 10.5% tantalum, 0.15 to 0.30% hafnium, 0.05 to 0.15% silicon, the balance being nickel and unavoidable impurities.
2. The superalloy according to claim 1, comprising, in percentages by mass, 4.0 to 5.5% rhenium, 3.5 to 8.5% cobalt, 0.30 to 1.50% molybdenum, 3.5 to 5.5% chromium, 3.5 to 4.5% tungsten, 4.5 to 6.0% aluminum, 0.50 to 1.50% titanium, 8.0 to 10.5% tantalum, 0.15 to 0.30% hafnium, 0.05 to 0.15% silicon, the balance being nickel and unavoidable impurities.
3. The superalloy according to claim 1, comprising, in percentages by mass, 4.0 to 5.5% rhenium, 3.5 to 12.5% cobalt, 0.30 to 1.50% molybdenum, 3.5 to 5.5% chromium, 3.5 to 5.5% tungsten, 5.0 to 6.0% aluminum, 0.35 to 1.50% titanium, 8.0 to 10.5% tantalum, 0.15 to 0.30% hafnium, 0.05 to 0.15% silicon, the balance being nickel and unavoidable impurities.
4. The superalloy according to claim 1, comprising, in percentages by mass, 4.5 to 5.5% rhenium, 4.0 to 6.0% cobalt, 0.30 to 1.00% molybdenum, 3.5 to 4.5% chromium, 3.5 to 4.5% tungsten, 4.5 to 6.0% aluminum, 0.50 to 1.50% titanium, 8.0 to 10.5% tantalum, 0.15 to 0.30% hafnium, 0.05 to 0.15% silicon, the balance being nickel and unavoidable impurities.
5. The superalloy according to claim 1, comprising, in percentages by mass, 4.5 to 5.5% rhenium, 3.5 to 12.5% cobalt, 0.50 to 1.50% molybdenum, 3.5 to 4.5% chromium, 3.5 to 4.5% tungsten, 5.0 to 6.0% aluminum, 0.50 to 1.50% titanium, 8.0 to 9.0% tantalum, 0.15 to 0.30% hafnium, 0.05 to 0.15% silicon, the balance being nickel and unavoidable impurities.
6. The superalloy according to claim 1, comprising, in percentages by mass, 4.5 to 5.5% rhenium, 7.0 to 9.0% cobalt, 0.50 to 1.50% molybdenum, 3.5 to 4.5% chromium, 3.5 to 4.5% tungsten, 5.0 to 6.0% aluminum, 0.50 to 1.50% titanium, 8.0 to 9.0% tantalum, 0.15 to 0.30% hafnium, 0.05 to 0.15% silicon, the balance being nickel and unavoidable impurities.
7. The superalloy according to claim 1, comprising, in percentages by mass, 4.2 to 5.3% rhenium, 6.0 to 8.0% cobalt, 0.30 to 1.00% molybdenum, 3.5 to 4.5% chromium, 4.5 to 5.5% tungsten, 5.0 to 6.0% aluminum, 0.35 to 1.30% titanium, 8.0 to 9.0% tantalum, 0.15 to 0.30% hafnium, 0.05 to 0.15% silicon, the balance being nickel and unavoidable impurities.
8. The superalloy according to claim 1, comprising, in percentages by mass, 4.0 to 5.0% rhenium, 4.0 to 6.0% cobalt, 0.30 to 1.00% molybdenum, 4.5 to 5.5% chromium, 3.5 to 4.5% tungsten, 5.0 to 6.0% aluminum, 0.35 to 1.30% titanium, 8.0 to 10.5% tantalum, 0.15 to 0.30% hafnium, 0.05 to 0.15% silicon, the balance being nickel and unavoidable impurities.
9. The superalloy according to claim 1, comprising, in percentages by mass, 5.2% rhenium, 5.0% cobalt, 0.50% molybdenum, 4.0% chromium, 4.0% tungsten, 5.4% aluminum, 1.00% titanium, 8.5% tantalum, 0.25% hafnium, 0.10% silicon, the balance being nickel and unavoidable impurities.
10. The superalloy according to claim 1, comprising, in percentages by mass, 5.2% rhenium, 5.0% cobalt, 0.50% molybdenum, 4.0% chromium, 4.0% tungsten, 5.4% aluminum, 1.00% titanium, 8.5% tantalum, 0.17% hafnium, 0.10% silicon, the balance being nickel and unavoidable impurities.
11. The superalloy according to claim 1, comprising, in percentages by mass, 5.2% rhenium, 5.0% cobalt, 0.50% molybdenum, 4.0% chromium, 4.0% tungsten, 5.1% aluminum, 1.00% titanium, 10.0% tantalum, 0.25% hafnium, 0.10% silicon, the balance being nickel and unavoidable impurities.
12. The superalloy according to claim 1, comprising, in percentages by mass, 5.0% rhenium, 12.0% cobalt, 1.00% molybdenum, 4.0% chromium, 4.0% tungsten, 5.4% aluminum, 1.00% titanium, 8.5% tantalum, 0.25% hafnium, 0.10% silicon, the balance being nickel and unavoidable impurities.
13. The superalloy according to claim 1, comprising, in percentages by mass, 5.0% rhenium, 4.0% cobalt, 1.00% molybdenum, 4.0% chromium, 4.0% tungsten, 5.4% aluminum, 1.00% titanium, 8.5% tantalum, 0.25% hafnium, 0.10% silicon, the balance being nickel and unavoidable impurities.
14. The superalloy according to claim 1, comprising, in percentages by mass, 4.9% rhenium, 8.0% cobalt, 1.00% molybdenum, 4.2% chromium, 4.0% tungsten, 5.4% aluminum, 1.00% titanium, 8.5% tantalum, 0.25% hafnium, 0.10% silicon, the balance being nickel and unavoidable impurities.
15. The superalloy according to claim 1, comprising, in percentages by mass, 4.9% rhenium, 8.0% cobalt, 1.00% molybdenum, 4.2% chromium, 4.0% tungsten, 5.4% aluminum, 1.00% titanium, 8.5% tantalum, 0.17% hafnium, 0.10% silicon, the balance being nickel and unavoidable impurities.
16. The superalloy according to claim 1, comprising, in percentages by mass, 4.9% rhenium, 8.0% cobalt, 1.00% molybdenum, 4.2% chromium, 4.0% tungsten, 5.4% aluminum, 1.00% titanium, 8.5% tantalum, 0.16% hafnium, 0.10% silicon, the balance being nickel and unavoidable impurities.
17. The superalloy according to claim 1, comprising, in percentages by mass, 4.7% rhenium, 7.0% cobalt, 0.50% molybdenum, 4.0% chromium, 5.0% tungsten, 5.4% aluminum, 0.80% titanium, 8.5% tantalum, 0.25% hafnium, 0.10% silicon, the balance being nickel and unavoidable impurities.
18. The superalloy according to claim 1, comprising, in percentages by mass, 4.5% rhenium, 5.0% cobalt, 0.50% molybdenum, 5.0% chromium, 4.0% tungsten, 5.4% aluminum, 1.00% titanium, 8.5% tantalum, 0.25% hafnium, 0.10% silicon, the balance being nickel and unavoidable impurities.
19. The superalloy according to claim 1, comprising, in percentages by mass, 4.5% rhenium, 5.0% cobalt, 0.50% molybdenum, 5.0% chromium, 4.0% tungsten, 5.4% aluminum, 0.55% titanium, 10.0% tantalum, 0.25% hafnium, 0.10% silicon, the balance being nickel and unavoidable impurities.
20. The superalloy according to claim 1, comprising, in percentages by mass, 4.3% rhenium, 5.0% cobalt, 0.50% molybdenum, 4.0% chromium, 4.0% tungsten, 5.4% aluminum, 1.00% titanium, 8.5% tantalum, 0.25% hafnium, 0.10% silicon, the balance being nickel and unavoidable impurities.
21. A single-crystal blade (20A, 20B) for a turbomachine comprising a superalloy according to any one of claims 1 to 20.
22. The blade (20A, 20B) according to claim 21, comprising a protective coating comprising a metallic bond coat deposited on the superalloy and a ceramic thermal barrier deposited on the metallic bond coat.
23. The blade (20A, 20B) according to claim 21 or 22, having a structure oriented in a <001> crystallographic direction.
24. A turbomachine comprising a blade (20A, 20B) according to any one of claims 21 to 23.

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