RU2774764C2 - Superalloy based on nickel, monocrystal blade and turbomachine - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention relates to metallurgy, in particular to superalloys based on nickel for gas turbines. The superalloy based on nickel contains, in wt.%: from 4.0 to 5.5 of rhenium, from 1.0 to 3.0 of ruthenium, from 2.0 to 14.0 of cobalt, from 0.30 to 1.00 of molybdenum, from 3.0 to 5.0 of chromium, from 2.5 to 4.0 of tungsten, from 4.5 to 6.5 of aluminum, from 0.50 to 1.50 of titanium, from 8.0 to 9.0 of tantalum, from 0.15 to 0.30 of hafnium, from 0.05 to 0.15 of silicon, the rest is nickel and unavoidable impurities. In this case, the superalloy has a monocrystal structure including allocations γ'-Ni₃(Al, Ti, Ta) dispersed in γ-matrix, with a size of 300-500 nm in the amount of 50-70 vol.%.

EFFECT: alloy is characterized by high resistance to high-temperature creep and improved resistance to corrosion and oxidation.

14 cl, 3 dwg, 7 tbl

Description

State of the art

The present disclosure relates to nickel-based superalloys for gas turbines, in particular for stationary blades, also known as "nozzles" or "rectifiers", or moving gas turbine blades, for example, in the aerospace industry.

Nickel-based superalloys are known to be used in fixed or movable monocrystalline gas turbine blades for aircraft and helicopter engines.

The main advantages of these materials are the combination of high resistance to creep fracture at high temperatures and resistance to oxidation and corrosion.

Over time, nickel-based superalloys for single-crystal blades have been subjected to significant changes in their chemical composition in order, in particular, to improve their creep characteristics at high temperatures while maintaining resistance to the very aggressive environment in which these superalloys are used.

In addition, metal coatings adapted to these alloys have been developed to increase their resistance to the harsh environments in which these alloys are used, including oxidation resistance and corrosion resistance. In addition, a low thermal conductivity ceramic coating can be added to reduce the temperature on the metal surface and act as a thermal barrier.

Typically, a complete protection system consists of at least two layers.

The first layer, also referred to as the underlayer or tie layer, is deposited directly onto the nickel-based superalloy component to be protected, also known as the "substrate", such as a blade. The deposition step is followed by a step of diffusion of the bonding layer into the superalloy. Deposition and diffusion can also be carried out in one stage.

Materials generally used to form this tie layer include alumina-forming 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 alloys of the nickel aluminide type (Ni _x Al _y ), some of which also contain platinum (Ni _x Al _y Pt _z ).

The second layer, commonly referred to as a thermal barrier coating (TBP), is a ceramic coating containing, for example, yttria-treated zirconia, also referred to as yttria-stabilized zirconia, (YSZ), or partially yttria-stabilized zirconia, (YPSZ), and having a porous structure. This layer can be deposited using a variety of methods such as electron beam physical vapor deposition (EB-PVD), atmospheric plasma sputtering (APS), slurry plasma sputtering (SPS) or other methods to produce a porous ceramic coating having low thermal conductivity. .

Due to the use of these materials at high temperatures, for example, from 650° C. to 1150° C., microscopic mutual diffusion phenomena occur between the nickel-based superalloy of the substrate and the metal alloy of the connecting layer. These interdiffusion phenomena associated with the oxidation of the tie layer modify, in particular, the chemical composition, microstructure and hence the mechanical properties of the tie layer, immediately after the production of the coating, and then during the use of the blade in the turbine. These interdiffusion phenomena also modify the chemical composition, microstructure and hence the mechanical properties of the superalloy of the substrate under the coating. Thus, in superalloys with a high content of refractory elements, in particular, rhenium, a secondary reaction zone (SRZ) can be formed in superalloys under the coating to a depth of several tens or even hundreds of micrometers. The mechanical characteristics of this VRZ zone are significantly lower than those of the superalloy substrate. The formation of the VRZ zone is undesirable because it leads to a significant decrease in the mechanical strength of the superalloy.

These changes in the tie layer, together with the stress fields associated with the growth of the alumina layer that forms during service on the surface of this tie layer, also known as "thermally grown oxide (TGO)", and the differences in thermal expansion coefficients between the different layers create decohesion. in the area of the interface between the sublayer and the ceramic coating, which can lead to partial or complete peeling of the ceramic coating. Thereafter, the metal part (superalloy substrate and metal bonding layer) is exposed to and directly exposed to the combustion gases, which increases the risk of damage to the blade and thus to the gas turbine.

In addition, the complex chemistry of these alloys can destabilize their optimum microstructure by exhibiting unwanted phase particles during high temperature exposure of parts formed from these alloys. This destabilization has negative consequences for the mechanical properties of these alloys. These unwanted phases with complex crystal structure and brittle nature are called topologically close-packed (TPU) phases.

In addition, casting defects can form in components such as blades when they are manufactured by directionally solidifying. These defects are usually "spotted" type grain defects, the presence of which can lead to premature failure of this part during operation. The presence of these defects associated with the chemical composition of the superalloy, usually leads to rejection of the component, which increases the cost of production.

Subject and essence of the invention

The present disclosure is directed to providing nickel-based superalloy compositions for the manufacture of single crystal components, with improved performance in terms of service life and mechanical strength, as well as reducing the cost of parts and reducing the rejection rate compared to existing alloys. These superalloys are characterized by higher creep resistance at high temperature compared to existing alloys, while showing good microstructure stability in the bulk of the superalloy (low sensitivity to TPU structure formation), good microstructure stability under the thermal barrier coating tie layer (low sensitivity to formation zones VRZ), good resistance to oxidation and corrosion while avoiding the formation of parasitic grains, belonging to the "spotted" type.

For this purpose, the present disclosure relates to a nickel-based superalloy containing, in mass percent in mass percent, from 4.0 to 5.5% rhenium, from 1.0 to 3.0% ruthenium, from 2.0 to 14, 0% cobalt, 0.30 to 1.00% molybdenum, 3.0 to 5.0% chromium, 2.5 to 4.0% tungsten, 4.5 to 6.5% aluminium, 0 .50 to 1.50% titanium, 8.0 to 9.0% 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 balance being nickel and unavoidable impurities.

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

With this nickel (Ni) based superalloy composition, creep resistance is improved over existing superalloys, in particular at temperatures up to 1200°C.

Therefore, this alloy is characterized by improved resistance to high temperature creep. This alloy also features improved corrosion and oxidation resistance.

These superalloys are characterized by a density less than or equal to 9.00 g/cm ³ (grams per cubic centimeter).

The nickel-based single crystal superalloy component is produced by a thermal gradient directionally solidified method during investment casting. The nickel-based single crystal superalloy contains an austenitic matrix having a face-centered cubic structure, which is a nickel-based solid solution known as "gamma phase (γ)". This matrix includes segregations of the strengthening gamma-prime phase (γ') having an ordered L1 ₂ cubic structure and belonging to the Ni ₃ Al type. Thus, this set (matrix and precipitates) is described as a γ/γ' superalloy.

In addition, this nickel-based superalloy composition allows a heat treatment to be carried out which brings back into solution the precipitated γ' phase and the γ/γ' eutectic phases that are formed during solidification of the superalloy. Thus, a nickel-based single-crystal superalloy comprising γ' precipitates having a controlled size, preferably in the range between 300 and 500 nanometers (nm), and containing a small proportion of γ/γ' eutectic phases, can be obtained.

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

The main alloying elements are cobalt (Co), chromium (Cr), molybdenum (Mo), rhenium (Re), ruthenium (RU), tungsten (W), aluminum (Al), titanium (Ti) and tantalum (Ta).

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

Inevitable impurities include sulfur (S), carbon (C), boron (B), yttrium (Y), lanthanum (La) and cerium (Ce). Unavoidable impurities are defined as those elements that are not intentionally added to the composition, and which are introduced together with other elements.

The addition of tungsten, chromium, cobalt, rhenium, ruthenium or molybdenum is mainly used to reinforce the austenitic matrix γ having a face centered cubic (fcc) crystal structure by solid solution strengthening.

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

Rhenium (Re) slows down the diffusion of chemicals in the superalloy and limits the coalescence of precipitates of the γ' phase during operation at high temperature, which is a phenomenon that leads to a decrease in mechanical strength. Thus, rhenium improves the creep resistance at high temperature of the nickel-based superalloy. However, an excessively high concentration of rhenium can lead to the formation of precipitates of intermetallic TPU phases, such as the σ phase, the P phase, or the μ phase, which adversely affect the mechanical properties of the superalloy. An excessive concentration of rhenium can also lead to the formation of a secondary reaction zone in the superalloy below the tie layer, which adversely affects the mechanical properties of the superalloy. In particular, the addition of ruthenium can displace some of the rhenium in the γ phase and limit the formation of TPU.

The simultaneous addition of silicon and hafnium improves the hot oxidation resistance of nickel-based superalloys by increasing the adhesion of the aluminum oxide (Al ₂ O ₃ ) layer that is formed on the surface of the superalloy at high temperature. This alumina layer forms a passivation layer on the surface of the nickel based superalloy and a barrier to oxygen diffusion from outside to inside of the nickel based superalloy. However, hafnium can also be added without adding silicon, or vice versa, silicon can also be added without adding hafnium, and the hot oxidation resistance of the superalloy can still be improved.

In addition, the addition of chromium or aluminum improves the resistance of the superalloy to oxidation and high temperature corrosion. In particular, chromium is essential in improving the hot corrosion resistance of nickel-based superalloys. However, an excessively high chromium content leads to a decrease in the dissolution temperature of the γ' phase of the nickel-based superalloy, i.e., the temperature above which the γ' phase completely dissolves in the γ matrix, which is undesirable. Therefore, the concentration of chromium is between 3.0 and 5.0 wt.% in order to maintain a high dissolution temperature of the γ' phase of the nickel-based superalloy, for example, greater than or equal to 1250°C, but also in order to avoid the formation of topologically compact phases in the γ matrix, which are highly saturated in alloying elements such as rhenium, molybdenum or tungsten.

The addition of cobalt, which is an element close to nickel and partially replaces nickel, leads to the formation of a solid solution with nickel in the γ matrix. Cobalt strengthens the γ matrix and reduces the susceptibility to the formation of TPU precipitates and the formation of the VRZ zone in the superalloy under the protective coating. However, an excessively high content of cobalt leads to a decrease in the dissolution temperature of the γ' phase of the nickel-based superalloy, which is undesirable.

The addition of ruthenium enhances the γ matrix and reduces the sensitivity of the superalloy to TPU formation. In particular, the addition of ruthenium makes it possible to replace some of the rhenium in the γ phase and limit the formation of TPU. The addition of ruthenium can also have a positive effect on the adhesion of the ceramic coating.

The addition of refractory elements such as molybdenum, tungsten, rhenium, or tantalum helps to slow down the mechanisms that control the creep of nickel-based superalloys, which depend on the diffusion of chemical elements into the superalloy.

The very low sulfur content of the nickel-based superalloy increases resistance to oxidation and hot corrosion, as well as resistance to thermal barrier spalling. Low sulfur content less than 2 ppm (wt.) (parts per million by weight) or ideally less than 0.5 ppm. (wt.), allows you to optimize these properties. This mass sulfur content can be obtained by producing a low sulfur mother melt or by using a post-casting desulfurization process. In particular, it is possible to keep the sulfur content low by adapting the superalloy production method.

Nickel-based superalloys are defined as superalloys with a predominant nickel content in mass percent in mass percent. In this regard, it must be understood that nickel is the element with the highest weight percentage in the alloy.

The superalloy may contain, in weight percent, 4.5 to 5.5% rhenium, 1.0 to 3.0 ruthenium, 3.0 to 5.0% cobalt, 0.30 to 0.80% molybdenum , 3.0 to 4.5% chromium, 2.5 to 4.0% tungsten, 4.5 to 6.5% 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, more preferably 0.20 to 0.30% hafnium, 0.05 to 0.15 % silicon, the rest are nickel and unavoidable impurities.

The superalloy may contain, in weight percent, 4.0 to 5.5% rhenium, 1.0 to 3.0% ruthenium, 3.0 to 13.0% cobalt, 0.40 to 1.00% molybdenum, 3.0 to 4.5% chromium, 2.5 to 4.0% tungsten, 4.5 to 6.5% aluminum, 0.50 to 1.50% titanium, 8.0 up 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 rest are nickel and unavoidable impurities.

The superalloy may contain, in weight percent, 4.0 to 5.0% rhenium, 1.0 to 3.0 ruthenium, 11.0 to 13.0% cobalt, 0.40 to 1.00% molybdenum , 3.0 to 4.5% chromium, 2.5 to 4.0% tungsten, 4.5 to 4.0 6.5% 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 up to 0.15% silicon, the rest is nickel and unavoidable impurities.

The superalloy may contain, in mass percent, 5.0% rhenium, 2.0 ruthenium, 4.0% cobalt, 0.50% molybdenum, 4.0% chromium, 3.0% tungsten, 5.4% aluminum, 1 .00% titanium, 8.5% tantalum, 0.25%. hafnium, 0.10% silicon, the rest are nickel and unavoidable impurities.

The superalloy may contain, in mass percent, 5.0% rhenium, 2.0 ruthenium, 4.0% cobalt, 0.50% molybdenum, 4.0% chromium, 3.5% tungsten, 5.4% aluminum, 0 .90% titanium, 8.5% tantalum, 0.25%. hafnium, 0.10% silicon, the rest are nickel and unavoidable impurities.

The superalloy may contain, in mass percent, 4.4% rhenium, 2.0 ruthenium, 4.0% cobalt, 0.70% molybdenum, 4.0% chromium, 3.0% tungsten, 5.4% aluminum, 1 .00% titanium, 8.5% tantalum, 0.25%. hafnium, 0.10% silicon, the rest are nickel and unavoidable impurities.

The superalloy may contain, in mass percent, 4.4% rhenium, 2.0 ruthenium, 12.0% cobalt, 0.70% molybdenum, 4.0% chromium, 3.0% tungsten, 5.4% aluminum, 1 .00% titanium, 8.5% tantalum, 0.25%. hafnium, 0.10% silicon, the rest are nickel and unavoidable impurities.

The superalloy may contain, in mass percent, 5.0% rhenium, 2.0 ruthenium, 4.0% cobalt, 0.50% molybdenum, 3.5% chromium, 3.5% tungsten, 5.4% aluminum, 0 .90% titanium, 8.5% tantalum, 0.25%. hafnium, 0.10% silicon, the rest are nickel and unavoidable impurities.

The superalloy may contain, in mass percent, 4.4% rhenium, 2.0 ruthenium, 12.0% cobalt, 0.70% molybdenum, 3.5% chromium, 3.5% tungsten, 5.4% aluminum, 0 .90% titanium, 8.5% tantalum, 0.25%. hafnium, 0.10% silicon, the rest are nickel and unavoidable impurities.

The present disclosure also relates to a single crystal turbomachine blade containing a superalloy as defined above.

Therefore, this blade is characterized by improved creep resistance at high temperatures.

The blade may comprise a protective coating including a metal bonding layer deposited on the superalloy and a ceramic thermal barrier deposited on the metal bonding layer.

Due to the composition of the nickel-based superalloy, the formation of a secondary reaction zone in the superalloy, which is the result of mutual diffusion phenomena between the superalloy and the sublayer, is eliminated or limited.

The metal bonding layer may be an MCrAlY type alloy or a nickel aluminide type alloy.

The ceramic thermal barrier may be a material based on zirconia treated with yttria or any other ceramic coating (based on silicon dioxide) having low thermal conductivity.

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

This orientation generally gives the blade optimal mechanical properties.

The present disclosure also relates to a turbomachine including a blade as defined above.

Brief description of the drawings

Other features and advantages of the invention will become apparent from the following description of the embodiments of the invention, presented by way of non-limiting examples, with reference to the single accompanying figure, in which:

fig. 1 is a schematic longitudinal sectional view of a turbomachine;

fig. 2 is a graph depicting the non-spotting parameter (NSP) for various superalloys;

fig. 3 is a graph showing the volume concentration of the γ' phase at various temperatures and for various superalloys.

Detailed description of the invention

Nickel-based superalloys are designed for the manufacture of single-crystal blades using a thermal gradient directional solidification process. This single crystal structure is made possible by the use of a single crystal seed or grain selector at the start of solidification. The structure is oriented, for example, in the <001> crystallographic direction, corresponding to the orientation that generally gives the superalloys optimum mechanical properties.

Solidified nickel-based single-crystal superalloys have a dendritic structure and consist of γ' Ni ₃ (Al, Ti, Ta) precipitates dispersed in a γ matrix having a face-centered cubic structure that forms a nickel-based solid solution. These phase separation γ' are heterogeneously distributed in the bulk of the single crystal due to chemical segregation resulting from the implementation of the method of solidification. In addition, γ/γ' eutectic phases are present in the interdendritic regions, which are the preferred centers of crack initiation. These eutectic phases γ/γ' are formed at the end of solidification. In addition, γ/γ' eutectic phases are formed to the detriment of fine precipitates (less than one micrometer in size) of the γ' hardening phase. The γ' phase precipitation data is the main source of hardening of nickel-based superalloys. Also, the presence of residual γ/γ' eutectic phases makes it impossible to optimize the hot creep resistance of the nickel-based superalloy.

Indeed, as has been demonstrated, the mechanical properties of superalloys, in particular creep resistance, were optimal when the formation of γ' precipitates was ordered, that is, when the γ' phase precipitates aligned regularly with a size in the range of 300 to 500 nm, and when the set of γ/γ' eutectic phases returned to the solution.

Therefore, freshly solidified nickel-based superalloys are subjected to heat treatment to obtain the desired distribution of the various phases. The first heat treatment is a homogenizing treatment of the microstructure, the purpose of which is to dissolve the precipitates of the γ' phase and eliminate the γ/γ' eutectic phases or significantly reduce their volume fraction. This treatment is carried out at a temperature greater than the dissolution temperature of the phase γ' and less than the melting start temperature of the superalloy (T _solidus ). Thereafter, at the end of this first heat treatment, quenching is carried out to obtain a fine and homogeneous dispersion of precipitates γ'. This is followed by tempering heat treatments in two stages at temperatures lower than the phase dissolution temperature γ'. In the first stage to grow the precipitates γ' to the desired size, and then in the second stage to increase the volume fractional concentration of this phase to approximately 70% at room temperature.

In FIG. 1 shows a vertical cross-section of a bypass turbojet 10 in a vertical plane passing through its main axis A. The turbojet 10 includes, in the direction of air movement from top to bottom, a fan 12, a low pressure compressor 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 includes a plurality of movable blades 20A co-rotating with the rotor and rectifiers 20B (stationary blades) mounted on the stator. Turbine stator 20 includes a plurality of stator rings 24 arranged opposite movable blades 20A of turbine 20.

Thus, these properties make these superalloys interesting candidates for the manufacture of single crystal parts for hot parts of turbojet engines.

Therefore, the movable blade 20A or the turbomachinery rectifier 20B can be made containing a superalloy as defined above.

Alternatively, the movable blade 20A or turbomachinery rectifier 20B containing the superalloy as defined above is coated with a protective coating containing a metallic bonding layer.

The turbomachine may in particular be a turbojet, such as the bypass turbojet 10. The turbomachine may also be a single-flow turbojet, turboprop, or turboshaft engine.

Examples

In the present disclosure, six nickel-based single crystal superalloys (Example 1 to Example 6) were studied and compared with six commercial single crystal superalloys CMSX-4 (Example 7), CMSX-4PlusC (Example 8), René N6 (Example 9), CMSX- 10 (example 10), MC-NG (example 11) and TMS-138 (example 12). The chemical composition of each of the single crystal superalloys is presented in Table 1, while the composition of example 9, in addition, contains 0.05 wt.% carbon (C) and 0.004 wt.% boron (B), the composition of example 10, in addition, contains 0 .10 wt% niobium (Nb). All superalloys are nickel-based superalloys, ie up to 100% of the compositions shown consist of nickel and unavoidable impurities.

Table 1

Re Ru co Mo Cr W Al Ti Ta hf Si Example 1 5.0 2.0 4.0 0.50 4.0 3.0 5.4 1.00 8.5 0.25 0.10 Example 2 5.0 2.0 4.0 0.50 4.0 3.5 5.4 0.90 8.5 0.25 0.10 Example 3 4.4 2.0 4.0 0.70 4.0 3.0 5.4 1.00 8.5 0.25 0.10 Example 4 4.4 2.0 12.0 0.70 4.0 3.0 5.4 1.00 8.5 0.25 0.10 Example 5 5.0 2.0 4.0 0.50 3.5 3.5 5.4 0.90 8.5 0.25 0.10 Example 6 4.4 2.0 12.0 0.70 3.5 3.5 5.4 0.90 8.5 0.25 0.10 Example 7 3.0 0.0 9.6 0.60 6.6 6.4 5.6 1.00 6.5 0.10 0.00 Example 8 4.8 0.0 10.0 0.60 3.5 6.0 5.7 0.85 8.0 0.10 0.00 Example 9 5.3 0.0 12.2 1.10 4.4 5.7 6.0 0.00 7.5 0.15 0.00 Example 10 6.0 0.0 3.0 0.40 2.0 5.0 5.7 0.20 8.0 0.03 0.00 Example 11 4.0 4.0 0.0 1.00 4.0 5.0 6.0 0.50 5.0 0.10 0.10 Example 12 4.9 2.0 5.9 2.9 2.9 5.9 5.9 0.00 5.6 0.10 0.00

Density

Density at room temperature for each superalloy was estimated using a modified version of Hull's formula (F. C. Hull, Metal Progress, November 1969, pp139-140). This empirical equation was proposed by Hull. The empirical equation is based on the law of mixtures and includes correction terms derived from a linear regression analysis of experimental data (chemical compositions and measured densities) for 235 superalloys and stainless steels. This Hull formula has been modified, in particular, to account for elements such as rhenium and ruthenium. Hull's modified formula is as follows:

(1) D = 27.68 × [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) × (% Ti) - 0.00096% Re - 0.001131% Ru],

where D ₁ \u003d 100 / [(% Cr / D _Cr ) + (% Ni / D _Ni ) + ... + (% X / D _X )],

where D _Cr , D _Ni , ..., D _X are the densities of the elements Cr, Ni, ..., X, in psi, and D is the density ^of the superalloy, in g/cm ³ ,

where %Cr, %Ni, ... %X are the content levels, in mass percent, for the superalloy elements Cr, Ni, ..., X.

Calculated densities for the alloys of the invention and for comparative alloys are less than 9.00 g/cm ³ (see table 2).

To test the modified Hull model (Equation (1)) the estimated and measured densities are compared (see Table 2). The estimated and measured densities agree with each other.

Table 2 shows the different parameters for the superalloys of examples 1-12.

table 2

Estimated density (1) (g/cm ³ ) Measured density (g/cm ³ ) POP GSHS

d

d Example 1 8.89 - 0.96 0.380 0.98 Example 2 - - 0.91 0.376 - Example 3 8.85 - 1.05 0.380 0.98 Example 4 8.83 - 1.05 0.380 0.98 Example 5 8.91 8.8 0.91 0.376 0.98 Example 6 8.86 - 1.00 0.376 0.98 Example 7 8.71 - 0.65 0.358 0.99 Example 8 8.91 - 0.68 0.371 0.99 Example 9 8.87 - 0.69 0.256 0.98 Example 10 8.99 - 0.67 0.299 0.96 Example 11 8.75 8.75 0.55 0.232 0.97 Example 12 8.88 - 0.61 0.215 0.97

No Spotting Parameter (NOP)

(2) POP = [%Ta + 1.5%Hf + 0.5%Mo - 0.5%Ti)]/[%W + 1.2%Re)],

where %Cr, %Ni, ...%X are the content levels, in mass percent, for the superalloy elements Cr, Ni, ..., X.

FOP is used to quantify sensitivity to mottling during preform directional solidification (US 5,888,451). To prevent the formation of spotting, the POP parameter should be greater than or equal to 0.7.

As can be seen in Table 2 and in Fig. 2, the superalloys of Examples 1-6 all have an OD value greater than or equal to 0.7, while the commercial superalloys of Examples 7-12 have an OD value of less than 0.7.

Gamma bar-fastness (GSHS)

The inherent mechanical strength of the γ' phase increases with an increase in the content of elements that replace aluminum in the Ni ₃ Al compound, such as titanium, tantalum, and some tungsten. Therefore, the γ' phase compound can be written as Ni ₃ (Al, Ti, Ta, W). The GSS parameter is used in assessing the level of hardening of the phase γ':

(3) GSS = [C _Ti + C _Ta + (C _W /2)]/C _Al ,

where C _Ti , C _Ta , C _W and C _Al are the concentrations, in atomic percent, for the elements Ti, Ta, W and Al, respectively, in the superalloy.

A higher GHS parameter is conducive to achieving better mechanical strength of the superalloy. As can be seen from Table 2, the GHS parameter calculated for the superalloys of Examples 1-6 is higher than the GHS parameter calculated for the commercial superalloys of Examples 7-12.

d) Sensitivity to the formation of TPU structures (

d)

d определяется следующим далее образом: Parameter

d is defined as follows:

, (four)

,

where X _i is the proportion of element i in the superalloy, in atomic percent, (Md) _i is the value of the parameter Md for element i.

Table 3 shows the Md values for various superalloy elements.

Table 3

Element md Element md Ti 2.271 hf 3.02 Cr 1.142 Ta 2.224 co 0.777 W 1.655 Ni 0.717 Re 1.267 Nb 2.117 Al 1.9 Mo 1.55 Si 1.9 Ru 1.006

d в соответствии с методом New PHACOMP, который был разработан авторами 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). В соответствии с данной моделью чувствительность суперсплавов к формированию структуры ТПУ увеличивается при увеличении значения параметра

d.The sensitivity to the formation of TPU structures is determined using the parameter

d according to the New PHACOMP method 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). In accordance with this model, the sensitivity of superalloys to the formation of the TPU structure increases with an increase in the value of the parameter

d.

d. Поэтому данные суперсплавы проявляют аналогичные чувствительности к формированию структур ТПУ, чувствительностями, которые имеют относительно низкие значения.As can be seen from table 2, the superalloys of examples 1 to 12 are characterized by approximately equal values of the parameter

d. Therefore, these superalloys exhibit similar sensitivities to the formation of TPU structures, sensitivities that are relatively low.

Phase dissolution temperature γ'

To calculate the phase dissolution temperature γ' at equilibrium, the ThermoCalc software (Ni25 database) based on the CALPHAD method was used.

As can be seen from Table 4, the superalloys of Examples 1-6 have a higher phase dissolution temperature γ' than the phase dissolution temperature γ' of the superalloys of Examples 7-12.

Volume fractional concentration of the phase γ'

ThermoCalc software (Ni25 database) based on the CALPHAD method was used to calculate the volume fraction (volume percent) of the γ' phase at equilibrium in the superalloys of Examples 1-12 at 950°C, 1150°C and 1200°C.

As can be seen from Table 4 and FIG. 3, the superalloys of Examples 1-6 have higher or comparable volume fractions of the γ' phase compared to the volume fractions of the γ' phase for the commercial superalloys of Examples 7-12.

Thus, the combination of a high dissolution temperature of the γ' phase and high volume fractions of the γ' phase for the superalloys of Examples 1 to 6 is favorable for good creep resistance at high and very high temperatures, for example at 1200°C. Therefore, this resistance must be greater than the creep resistance of the commercial superalloys of Examples 7-12.

Table 4

T phase _dissolution γ' (°C) Volume fractional concentration of the phase γ’ (% (vol.)) 950°C 1050°C 1200°C Example 1 1338 67.0 62.0 46.0 Example 2 1335 67.6 62.4 45.9 Example 3 1337 66.6 61.1 43.2 Example 4 1276 60.0 51.2 22.7 Example 5 1344 65.0 60.0 46.0 Example 6 1295 58.0 50.0 38.0 Example 7 1290 58.0 48.0 25.0 Example 8 1320 63.0 57.0 36.0 Example 9 1283 60.0 51.0 24.0 Example 10 1374 65.0 60.0 46.0 Example 11 1348 68.0 62.0 45.0 Example 12 1321 67.0 58.0 35.0

Volume fractional concentration of the phase σ related to the TPU type

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

d). The calculated volume fractions for the σ phase are zero at 950°C for the superalloys of examples 3,4 and 6 and are relatively low for the superalloys of examples 1 and 5, which reflects the low sensitivity to the formation of precipitates of TPU structures. Therefore, these results reinforce the results obtained using the New PHACOMP method (parameter

d).

Mass concentration of chromium dissolved in the matrix γ

ThermoCalc software (Ni25 database) based on the CALPHAD method was used to calculate the chromium content (in weight percent) in the γ phase at equilibrium in the superalloys of Examples 1-14 at 950°C, 1050°C and 1200°C.

As can be seen from Table 5, the chromium concentrations in the γ phase are higher for the superalloys of Examples 1-6 compared to the chromium concentrations in the γ phase for the commercial superalloys of Examples 7-12, which favors better hot corrosion and oxidation resistance.

Table 5

Volume fractional concentration of the phase σ, related to the type of TPU, (in% (vol.)) Level of chromium content in phase γ
(in % (mass.)) 950°C 1050°C 950°C 1050°C 1200°C Example 1 0.4 0.00 8.80 7.80 6.00 Example 2 0.00 0.00 11.30 9.90 7.30 Example 3 0.0 0.00 8.50 7.60 5.80 Example 4 0.0 0.00 8.10 5.50 4.80 Example 5 0.7 0.05 8.70 7.90 6.30 Example 6 0.0 0.00 8.10 7.00 5.20 Example 7 0.7 0.00 12.80 10.90 7.84 Example 8 1.2 0.50 7.40 6.43 4.82 Example 9 1.0 0.25 8.37 7.10 5.25 Example 10 0.9 0.40 3.62 3.36 2.77 Example 11 0.8 0.20 7.83 7.10 5.70 Example 12 0.4 0.60 5.60 4.80 3.70

Creep characteristics at very high temperature

Creep tests were carried out on superalloys of example 2, example 7, example 9, example 10. Creep tests were carried out at 1200°C and 80 MPa in accordance with the NF EN ISO 204 standard of August 2009 (Guide U125_J).

The results of the creep tests in which the superalloys were loaded (80 MPa) at 1200° C. are shown in Table 6. The results are the time in hours (hour) at sample failure.

Table 6

Time to failure (hour) Example 2 63 Example 7 7 Example 9 9 Example 10 59

The superalloy of example 2 shows better creep characteristics than the superalloys of example 7 and example 9. The superalloy of example 10 also shows good creep characteristics.

Characteristics of cyclic oxidation at 1150°C

Superalloys are thermally cycled as described in INS-TTH-001 and INS-TTH-002: Oxidative Cycling Test Method (Mass Loss Test and Thermal Barrier).

The superalloy sample being tested (a pin having a diameter of 20 mm and a height of 1 mm) is subjected to thermal cycling, each cycle of which includes an increase in temperature to 1150 ° C for less than 15 min (minutes), a 60-minute stop at 1150 ° C and turbine cooling sample for 15 minutes.

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

Service life for the superalloys tested is shown in Table 7.

Table 7

Operating life (hours) Example 2 > 1700 Example 7 ~ 230 Example 8 ~ 480 Example 10 ~ 100

As can be seen, the superalloy of example 2 has a much longer service life than the superalloys of example 7, example 8 and example 9. It should be noted that the oxidation characteristics of the superalloy of example 10 are much worse than those of the superalloy of example 2.

Microstructure stability

After aging for 300 hours at 1050° C. as a result of image analysis by scanning electron microscopy, no TPU phase was observed for the superalloy of example 2.

Sensitivity to the formation of casting defects

After casting by lost wax casting and directionally solidifying in a Bridgman furnace, the superalloy of Example 2 did not observe any defects representing the result of casting, in particular those of the "mottled" type. Defects related to the "spotted" type, observed after immersion of the sample in a solution based on HNO ₃ /H ₂ SO ₄ .

Although the present disclosure has been described with reference to a specific example of a specific embodiment, it is obvious that various modifications and changes can be made to these examples without going beyond the general scope of the invention, which is defined by the claims. In addition, individual features of the various embodiments mentioned may be combined in additional embodiments. Therefore, the description and drawings are to be considered in an illustrative and not a limiting sense.

Claims (14)

1. Nickel-based superalloy containing in wt.%: 4.0 to 5.5 rhenium, 1.0 to 3.0 ruthenium, 2.0 to 14.0 cobalt, 0.30 to 1, 00 molybdenum, 3.0 to 5.0 chromium, 2.5 to 4.0 tungsten, 4.5 to 6.5 aluminum, 0.50 to 1.50 titanium, 8.0 to 9, 0 tantalum, from 0.15 to 0.30 hafnium, from 0.05 to 0.15 silicon, the rest is nickel and inevitable impurities, while it has a single-crystal structure, including γ'-Ni ₃ precipitates dispersed in the γ-matrix ( Al, Ti, Ta) with a size of 300-500 nm in the amount of 50-70 vol.%. 2. Superalloy according to claim 1, characterized in that it contains in wt.%: from 4.5 to 5.5 rhenium, from 1.0 to 3.0 ruthenium, from 3.0 to 5.0 cobalt, from 0.30 to 0.80 molybdenum, 3.0 to 4.5 chromium, 2.5 to 4.0 tungsten, 4.5 to 6.5 aluminum, 0.50 to 1.50 titanium, from 8.0 to 9.0 tantalum, 0.15 to 0.30 hafnium, 0.05 to 0.15 silicon, the rest is nickel and inevitable impurities. 3. Superalloy according to claim 1, characterized in that it contains in wt.%: from 4.0 to 5.5 rhenium, from 1.0 to 3.0 ruthenium, from 3.0 to 13.0 cobalt, from 0.40 to 1.00 molybdenum, 3.0 to 4.5 chromium, 2.5 to 4.0 tungsten, 4.5 to 6.5 aluminum, 0.50 to 1.50 titanium, from 8.0 to 9.0 tantalum, 0.15 to 0.30 hafnium, 0.05 to 0.15 silicon, the rest is nickel and inevitable impurities. 4. Superalloy according to claim 1, characterized in that it contains in wt.%: from 4.0 to 5.0 rhenium, from 1.0 to 3.0 ruthenium, from 11.0 to 13.0 cobalt, from 0.40 to 1.00 molybdenum, 3.0 to 4.5 chromium, 2.5 to 4.0 tungsten, 4.5 to 6.5 aluminum, 0.50 to 1.50 titanium, from 8.0 to 9.0 tantalum, 0.15 to 0.30 hafnium, 0.05 to 0.15 silicon, the rest is nickel and inevitable impurities. 5. Superalloy according to claim 1, characterized in that it contains in wt.%: 5.0 rhenium, 2.0 ruthenium, 4.0 cobalt, 0.50 molybdenum, 4.0 chromium, 3.0 tungsten, 5 .4 aluminum, 1.00 titanium, 8.5 tantalum, 0.25 hafnium, 0.10 silicon, the rest is nickel and inevitable impurities. 6. Superalloy according to claim 1, characterized in that it contains in wt.%: 4.4 rhenium, 2.0 ruthenium, 4.0 cobalt, 0.70 molybdenum, 4.0 chromium, 3.0 tungsten, 5 .4 aluminum, 1.00 titanium, 8.5 tantalum, 0.25 hafnium, 0.10 silicon, the rest is nickel and inevitable impurities. 7. Superalloy according to claim 1, characterized in that it contains in wt.%: 4.4 rhenium, 2.0 ruthenium, 12.0 cobalt, 0.70 molybdenum, 4.0 chromium, 3.0 tungsten, 5 .4 aluminum, 1.00 titanium, 8.5 tantalum, 0.25 hafnium, 0.10 silicon, the rest is nickel and inevitable impurities. 8. Superalloy according to claim 1, characterized in that it contains in wt.%: 5.0 rhenium, 2.0 ruthenium, 4.0 cobalt, 0.50 molybdenum, 3.5 chromium, 3.5 tungsten, 5 .4 aluminum, 0.90 titanium, 8.5 tantalum, 0.25 hafnium, 0.10 silicon, the rest is nickel and inevitable impurities. 9. Superalloy according to claim 1, characterized in that it contains in wt.%: 5.0 rhenium, 2.0 ruthenium, 4.0 cobalt, 0.50 molybdenum, 4.0 chromium, 3.5 tungsten, 5 .4 aluminum, 0.90 titanium, 8.5 tantalum, 0.25 hafnium, 0.10 silicon, the rest is nickel and inevitable impurities. 10. Superalloy according to claim 1, characterized in that it contains in wt.%: 4.4 rhenium, 2.0 ruthenium, 12.0 cobalt, 0.70 molybdenum, 3.5 chromium, 3.5 tungsten, 5 .4 aluminum, 0.90 titanium, 8.5 tantalum, 0.25 hafnium, 0.10 silicon, the rest is nickel and inevitable impurities. 11. Monocrystalline blade (20A, 20B) for a turbomachine, made of a superalloy according to any one of paragraphs. 1-10. 12. A blade (20A, 20B) according to claim 11, characterized in that it has a protective coating comprising a metal bonding layer deposited on the superalloy and a ceramic thermal barrier deposited on the metal bonding layer. 13. Blade (20A, 20B) according to claim 11 or 12, characterized in that the structure is oriented in the <001> crystallographic direction. 14. Turbomachine, including a blade (20A, 20B) according to any one of paragraphs. 11-13.

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