JP2021523985A - Nickel-based alloy - Google Patents

Abstract

By mass%, 9.0 to 13.2% chromium, 5.9 to 24.9% cobalt, 0.0 to 4.0% iron, 1.1 to 4.4% molybdenum, 0. 0-8.0% tungsten, 2.8-3.7% aluminum, 0.3-5.1% tantalum, 0.0-4.0% niobium, over 2.4% 9.5 % Or less tantalum, 0.01-0.1% carbon, 0.001-0.1% molybdenum, 0.001-0.3% zirconium, 0.0-0.5% silicon, 0 .0 to 0.1% molybdenum, 0.0 to 0.1% tantalum, 0.0 to 0.1% cerium, 0.0 to 0.003% sulfur, 0.0 to 0.25 With% manganese, 0.0-0.5% vanadium, 0.0-0.5% copper, and 0.0-0.5% hafnium, the balance is nickel and unavoidable impurities. When the mass% of molybdenum, tungsten, niobium, tantalum and titanium contained in the alloy are WMo, WW, WNb, WTa and WTi, respectively, a nickel-based alloy composition satisfying the following formula. 1.29WMo + 0.5WW ≧ 5.70.6WTi + 0.44WNb + 0.27WTa ≧ 4.2

Description

The present invention relates to nickel-based superalloy compositions used as turbine disk components in gas turbine engines and other turbomachinery.

Turbine disks are an important component in gas turbine engines. Improving the performance of turbine disc alloys in terms of maximum operating temperature and maximum service life can have a significant impact on engine efficiency and cost-effectiveness of engine operation.

Table 1 lists examples of typical compositions of nickel-based superalloys used in turbine disc components. With reference to FIG. 1, in the development of alloys with higher strength, the cost tends to go to higher levels. Table 1 shows the nominal composition in% by mass of commonly applied nickel-based superalloys used in powder metallurgy turbine discs.

It is an object of the present invention to provide high high temperature strength and creep resistance in combination with low alloy cost (preferably reduction of alloy cost) and improvement of oxidation resistance / corrosion resistance. The balance of properties of the new alloy can further increase cost effectiveness in the manufacture of parts for high temperature applications (particularly for turbine disc applications where the operating temperature of the part is 800 degrees or higher).

According to the present invention, by mass%, 9.0 to 13.2% chromium, 5.9 to 24.9% molybdenum, 0.0 to 4.0% iron, 1.1 to 4.4. % Molybdenum, 0.0-8.0% tungsten, 2.8-3.7% aluminum, 0.3-5.1% tantalum, 0.0-4.0% niobium, 2. More than 4% and less than 9.5% tantalum, 0.01 to 0.1% carbon, 0.001 to 0.1% molybdenum, 0.001 to 0.3% zirconium, 0.0 to 0. 5% silicon, 0.0-0.1% molybdenum, 0.0-0.1% tantalum, 0.0-0.1% cerium, 0.0-0.003% sulfur, 0 .0 to 0.25% manganese, 0.0 to 0.5% vanadium, 0.0 to 0.5% copper, and 0.0 to 0.5% hafnium, with the balance being nickel and A nickel-based alloy that is an unavoidable impurity and satisfies the following formula, where the mass% of molybdenum, tungsten, niobium, tantalum, and titanium contained in the alloy are W _Mo , W _W , W _Nb , W _Ta, and W _{Ti, respectively.} The composition is provided.
1.29W _Mo + 0.5W _W ≧ 5.7
0.6W _Ti + 0.44W _Nb + 0.27W _Ta ≧ 4.2

This alloy, combined with excellent oxidation / corrosion resistance and resistance to TCP formation, provides very high strength at high temperatures.

In a preferred embodiment, where the mass% of niobium, tantalum, titanium and aluminum contained in the alloy are W _Nb , W _Ta , W _Ti and W _Al , respectively, the following formula is satisfied.
6.2 ≤ 0.6W _Ti + _{0.31W Nb} + 0.15W _Ta + 0.94W _Al ≤ 7.4
Preferably, the following formula is satisfied.
6.2 ≤ 0.6W _Ti + _{0.31W Nb} + 0.15W _Ta + 0.94W _Al ≤ 6.7
This ensures a gamma prime phase sufficient to impart high strength to the alloy.

In a preferred embodiment, where the mass% of niobium, tantalum, titanium and aluminum contained in the alloy are W _Nb , W _Ta , W _Ti and W _Al , respectively, the following formula is satisfied.
1.0 ≤ (0.6W _Ti + _{0.31W Nb} + 0.15W _Ta ) / W _Al ≤ 1.3
This guarantees an alloy with high APB energy and a stable gamma prime phase. As such, the alloy has excellent resistance to precipitation shear and resistance to the formation of eta and delta phases.

In a preferred embodiment, the weight percent of tungsten and molybdenum contained in the alloy, respectively W _W, When W _Mo, satisfy the following equation.
6.0 ≤ 1.29 _{W Mo} + 0.5 _{W W}
Since such an alloy has a high solid solution merit index, resistance to high temperature creep is improved and high temperature strength is improved.

In a preferred embodiment, where the mass% of tantalum and tungsten contained in the alloy are W _Ta and W _W , respectively, the following equation is satisfied.
W _Ta + 0.88 _{W W} ≤ 9.4
Such alloys have a lower density than alloys that do not satisfy the above formula.

In a preferred embodiment, where the mass% of tantalum and cobalt contained in the alloy are W _Ta and W _Co , respectively, the following formula is satisfied.
W _Ta + 0.47 _{W Co} ≤ 14.1
Costs are limited for such alloys.

In a preferred embodiment, where the mass% of tungsten, molybdenum and chromium contained in the alloy are _WW , _WM and W _Cr , respectively, the following equation is satisfied.
_{W W + 1.62W Cr + 2.0W Mo} ≦ 30.2
Preferably, the following formula is satisfied.
_{W W + 1.62W Cr + 2.0W Mo} ≦ 28.3
Such alloys are highly resistant to the formation of harmful TCP phases.

In a preferred embodiment, the aluminum content of the nickel-based alloy composition is 3.5% or less, preferably 3.1% or less, by mass. Such alloys have a low gamma prime solver temperature, which improves manufacturability.

In a preferred embodiment, the tantalum contained in the nickel-based alloy composition is 2.45% or more, preferably 2.5% or more, more preferably 3.4% or more, still more preferably 5.1% by mass. That is all. Such alloys have higher strength at the cost of lower gamma prime sorbus temperature.

In a preferred embodiment, the tantalum content of the nickel-based alloy composition is 6.4% or less by mass. In such alloys, the gamma prime solver temperature is limited, so ease of manufacture is maintained.

In a preferred embodiment, the niobium contained in the nickel-based alloy composition is 1.0% or more by mass. Such alloys have improved strength.

In a preferred embodiment, the niobium contained in the nickel-based alloy composition is 3.0% or less, preferably 2.0% or less in mass%. Such alloys have improved strength.

In a preferred embodiment, the titanium content of the nickel-based alloy composition is 1.7% or more, preferably 2.5% or more in mass%. Such alloys have improved strength.

In a preferred embodiment, the content of titanium contained in the nickel-based alloy composition is 4.8% or less, preferably 4.6% or less, and more preferably 4.2% or less in terms of mass%. Such alloys have better oxidation resistance and improved manufacturability.

In a preferred embodiment, the content of tungsten contained in the nickel-based alloy composition is 3.2% or more in mass%. Such alloys have excellent high temperature strength.

In a preferred embodiment, the content of tungsten contained in the nickel-based alloy composition is 7.8% or less, preferably 6.9% or less in mass%. Such alloys have a low density.

In a preferred embodiment, the molybdenum contained in the nickel-based alloy composition is 1.2% or more, preferably 1.7% or more in mass%. Such alloys have higher solid solution strength, which improves creep strength.

In a preferred embodiment, the cobalt content of the nickel-based alloy composition is 6.1% or more, preferably 7.1% or more, by mass. Such alloys have improved strength, especially creep resistance.

In a preferred embodiment, the cobalt content of the nickel-based alloy composition is 24.6% or less, preferably 22.8% or less, more preferably 19.1% or less, and even 16.8% or less, in mass%. It is 16.6% or less, even more preferably 14.7% or less, and most preferably 11.1% or less. Such alloys are low cost.

In a preferred embodiment, the amount of chromium contained in the nickel-based alloy composition is 11.9% or less, preferably 11.5% or less, and more preferably 11.2% or less in mass%. Such an alloy has improved microstructural stability from the viewpoint of resistance to the formation of the TCP phase.

The term "comprising" as used herein is used to indicate that the composition is 100% and the percentage is 100% by excluding the presence of additional ingredients. Unless otherwise stated,% is expressed as% by mass.

The present invention will be described in more detail with reference to the accompanying drawings, only by way of illustration.

FIG. 1 shows the calculated trade-off between elemental cost and yield strength (in terms of strength merit index) for the alloys listed in Table 1 and the alloys located within the alloy design areas listed in Table 2. Is shown. The hatched areas on the graph indicate the preferred combination of strength and cost. FIG. 2 shows the calculated relationship between yield strength (in terms of intensity merit index) and volume fraction of the γ'phase at 850 ° C. The minimum value of the γ'volume fraction required to achieve the desired level of intensity merit index is highlighted. FIG. 3 shows the total effect of aluminum and niobium element (based on the relationship between _{0.6 W Ti} + 0.31 _{W Nb} + 0.15 W _Ta ), titanium element and tantalum element on the γ'volume fraction at 900 ° C. It is a contour figure which shows. The graph also shows the composition dependence of γ'solvus and intensity. FIG. 4 is a contour diagram showing the total effect of aluminum and niobium element (based on the relationship with _{0.6 W Ti} + 0.31 _{W Nb} + 0.15 W _{Ta), titanium element and tantalum element on γ'solvus temperature.} Is. FIG. 5 is a contour diagram showing the effects of titanium and tantalum on the strength merit index in an alloy having a volume fraction of γ'of 0.51 to 0.62. In this alloy, the aluminum content is fixed at 2.8-3.7% by mass and the niobium content is fixed at 0.0% by weight. FIG. 6 is a contour diagram showing the effects of titanium and tantalum on the strength merit index in an alloy having a volume fraction of γ'of 0.51 to 0.62. In this alloy, the aluminum content is fixed at 2.8-3.7% by mass and the niobium content is fixed at 1.0% by weight. FIG. 7 is a contour diagram showing the effects of titanium and tantalum on the strength merit index in an alloy having a volume fraction of γ'of 0.51 to 0.62. In this alloy, the aluminum content is fixed at 2.8-3.7% by mass and the niobium content is fixed at 2.0% by weight. FIG. 8 is a contour diagram showing the effects of titanium and tantalum on the strength merit index in an alloy having a volume fraction of γ'of 0.51 to 0.62. In this alloy, the aluminum content is fixed at 2.8-3.7% by mass and the niobium content is fixed at 3.0% by weight. FIG. 9 is a contour diagram showing the effects of titanium and tantalum on the strength merit index in an alloy having a volume fraction of γ'of 0.51 to 0.62. In this alloy, the aluminum content is fixed at 2.8-3.7% by mass and the niobium content is fixed at 4.0% by weight. FIG. 10 is a contour diagram showing the effects of molybdenum and tungsten on the solid solution merit index in an alloy having a volume fraction of γ'of 0.51 to 0.62. FIG. 11 is a contour diagram showing the effects of tantalum and tungsten on the alloy density in an alloy having a volume fraction of γ'of 0.51 to 0.62. FIG. 12 shows the effect of cobalt and tantalum on alloy costs (in terms of raw element costs based on 2017 element prices) in alloys with a volume fraction of γ'of 0.51 to 0.62. It is a contour diagram. FIG. 13 is a contour diagram showing the effect of cobalt and tungsten on creep resistance (from the viewpoint of creep merit index) in an alloy having a volume fraction of γ'of 0.51 to 0.62. .. The molybdenum content in this alloy is fixed at 1.0% by mass. FIG. 14 is a contour diagram showing the effect of cobalt and tungsten on creep resistance (from the viewpoint of creep merit index) in alloys having a volume fraction of γ'of 0.51 to 0.62. .. The molybdenum content in this alloy is fixed at 2.0% by mass. FIG. 15 is a contour diagram showing the effect of cobalt and tungsten on creep resistance (from the viewpoint of creep merit index) in alloys having a volume fraction of γ'of 0.51 to 0.62. .. The molybdenum content in this alloy is fixed at 3.0% by mass. FIG. 16 is a contour diagram showing the effect of cobalt and tungsten on creep resistance (from the viewpoint of creep merit index) in alloys having a volume fraction of γ'of 0.51 to 0.62. .. The molybdenum content in this alloy is fixed at 4.0% by mass. FIG. 17 is a contour diagram showing the effects of cobalt and tungsten on creep resistance (from the viewpoint of creep merit index) in alloys having a volume fraction of γ'of 0.51 to 0.62. .. The molybdenum content in this alloy is fixed at 5.0% by mass. FIG. 18 is a contour diagram showing the effects of chromium and tungsten on the stability number Md in an alloy having a volume fraction of γ'of 0.51 to 0.62. The molybdenum content in this alloy is fixed at 0.0% by mass. FIG. 19 is a contour diagram showing the effects of chromium and tungsten on the stability number Md in an alloy having a volume fraction of γ'of 0.51 to 0.62. The molybdenum content in this alloy is fixed at 1.0% by mass. FIG. 20 is a contour diagram showing the effects of chromium and tungsten on the stability number Md in an alloy having a volume fraction of γ'of 0.51 to 0.62. The molybdenum content in this alloy is fixed at 2.0% by mass. FIG. 21 is a contour diagram showing the effects of chromium and tungsten on the stability number Md in an alloy having a volume fraction of γ'of 0.51 to 0.62. The molybdenum content in this alloy is fixed at 3.0% by mass. FIG. 22 is a contour diagram showing the effects of chromium and tungsten on the stability number Md in an alloy having a volume fraction of γ'of 0.51 to 0.62. The molybdenum content in this alloy is fixed at 4.0% by mass. FIG. 23 is a contour diagram showing the effects of chromium and tungsten on the stability number Md in an alloy having a volume fraction of γ'of 0.51 to 0.62. The molybdenum content in this alloy is fixed at 5.0% by mass.

Traditionally, nickel-based superalloys have been designed on an empirical basis. Therefore, the chemical composition of nickel-based superalloys has been identified by time-consuming and expensive experimental developments, including small-scale processing of limited amounts of material and subsequent property analysis of behavior. Then an alloy composition found to exhibit the best, or most desirable combination of properties, is adopted. The presence of a large number of alloying elements that can achieve this combination indicates that these alloys are not fully optimized and are likely to have better alloys.

In superalloys, chromium (Cr) and aluminum (Al) are generally added to impart oxidation resistance / corrosion resistance, and cobalt (Co) is added to improve resistance to sulfide. Molybdenum (Mo), tungsten (W) and cobalt (Co) are introduced for creep resistance, which is a thermal activation process in which these elements determine the rate of creep deformation (eg, dislocations). This is to prevent the rise). Aluminum (Al), tantalum (Ta), niobium (Nb) and titanium (Ti) are introduced to increase static and repeat strength, which means that these elements are precipitation-hardened phase gamma prime. This is to promote the formation of γ'). This precipitated phase is coherent with a face-centered cubic (FCC) matrix phase called gamma (γ).

As used herein, a model-based approach used to identify new grades of nickel-based superalloys is described in terms of the "alloy design" (ABD) method. This technique utilizes a computational material model framework for estimating design-related properties over a very wide range of compositional areas. In principle, this alloy design tool can solve the so-called inverse problem. That is, the optimum alloy composition that most satisfies the specified design constraints can be specified.

The first step in the design process is to define the elemental table and the upper and lower limits of the composition restrictions associated with the elemental table. In the present invention, a composition limitation for each element when adding each element, which is called an "alloy design area", is taken into consideration. This composition restriction is detailed in Table 2. Table 2 shows the alloy design areas studied.

The second step is based on thermodynamic calculations to calculate the phase diagram and thermodynamic properties of a particular alloy composition. This is often referred to as the CALPHAD method (CALculate PHAse Diagram). Performing these calculations at the typical operating temperature (900 ° C.) of the new alloy provides information about phase equilibrium (microstructure).

The third step involves identifying an alloy composition having the desired microstructure. In the case of nickel-based superalloys that require excellent resistance to creep deformation, the creep rupture life is gradually improved as the volume fraction of the precipitation hardening phase γ'increases. The range of volume fraction of γ'where creep break life is most beneficial is 60-70% at 900 ° C. (however, other design constraints limit the volume fraction to lower values. Includes alloys with a γ'volume fraction of 50% to 60%). When the volume fraction of γ'exceeds 70%, a decrease in creep resistance is observed.

In addition, since γ / γ'lattice irregularity loses coherency, it is necessary to follow a smaller value of positive and negative. Therefore, the limit depends on the absolute value of that value. Lattice irregularity δ is defined as an inconsistency between the γ phase and the γ'phase, and is calculated by the following equation.

Here, α _γ and α _γ'are lattice constants of the γ phase and the γ'phase.

Therefore, this model identifies all compositions in the design area where the calculation result of the volume fraction of γ'is the desired value. In these compositions, the lattice irregularity of γ'is less than a predetermined absolute value.

In the fourth stage, a merit index is estimated for the identified alloy compositions remaining in the dataset. The merit index includes creep merit index (indicating creep resistance of alloy based only on average composition), strength merit index (indicating an alloy's precipitation yield strength based only on average composition), density, and Includes cost, microstructural stability and gamma prime sorbus temperature.

In the fifth stage, the calculated merit index is compared to the constraints on the desired behavior and these design constraints are considered as boundary conditions for the problem. All compositions that do not meet the boundary conditions are rejected. At this stage, the size of the test data set is very small.

The final sixth step involves analyzing the dataset of the remaining composition. This analysis can be done in a variety of ways. For one thing, alloys having the maximum merit index may be classified via a database. The alloy having the maximum merit index is, for example, the lightest alloy, the alloy with the highest creep resistance, the alloy with the highest oxidation resistance, and the cheapest alloy. Alternatively, a database may be used to determine the relative performance trade-offs caused by the combination of different properties.

The seven merit indexes will be described.

The first merit index is the creep merit index. The most important observation is that the time-dependent deformation (ie, creep) of the nickel-based superalloy is caused by dislocation creep with initial activity limited to the γ phase. Therefore, the dislocation segment is rapidly fixed at the γ / γ'interface due to the large proportion of the γ'phase. The rate-determining step is the departure of the trapped configuration of dislocations from the γ / γ'interface. It depends on the local chemistry (in this case the composition of the γ phase) that causes the significant effect of the alloy composition on the creep properties.

The physics-based microstructure model is used for the rate of accumulation of ^{creep strain ε ·} when the load is uniaxial and along the <001> crystallographic direction. The set equation is the following equation.

Here, ρ _m is the movable dislocation density, φ _p is the volume fraction of the γ'phase, and ω is the width of the matrix channel. The terms σ and Τ are working stress and temperature, respectively. The terms b and k are Burgers vector and Boltzmann constant, respectively. The term K _CF is the constraint factor.

The term K _CF indicates the proximity of cubic particles in these alloys. Equation 3 shows the dislocation multiplication process that requires the multiplication parameter C and the estimation of the initial dislocation density. The term D _eff is an effective diffusivity that controls the ascending process at the particle / matrix interface.

In the above contents, the composition dependence arises from the two terms φ _p and D _eff . Therefore, assuming that the microstructure is constant (most of the microstructure is controlled by heat treatment), the dependence on the chemical composition is caused by _{Deff because φp is fixed.} It can be seen that for the purposes of alloy design modeling described herein, it is not necessary to perform the complete integration of Equations 2 and 3 for each prototype alloy composition. _{Instead, the primary merit index Mcreep} , which needs to be maximized, is used. M _creep is calculated by the following formula.

Here, x _i is the atomic fraction of the solute i in the γ phase. _Di ^~ is an appropriate mutual diffusion coefficient.

The second merit index is the strength merit index. For high nickel-based superalloys, most of the strength comes from the precipitated phase. Therefore, optimizing the alloy composition to maximize precipitation strength is an important design consideration. Based on the curing theory, the strength merit index M _strength is proposed. This index takes into account the maximum possible precipitation strength (determined as the point at which the dislocation shear transition from a weak bond to a strong bond occurs) and is approximated using the formula below.

Here, M− is the Taylor coefficient, γ _APB is the antiphase boundary (APB) energy, φ _p is the volume fraction of the γ'phase, and b is the Burgers vector.

From equation (5), it is clear that the defect energy in the γ'phase (for example, the anti-phase boundary APB energy) has a great influence on the deformation behavior of the nickel-based superalloy. Increasing APB energy has been found to improve mechanical properties, including tensile strength and resistance to creep deformation. Studies of APB energies have been carried out on many Ni-Al-X systems using density functional theory. This study calculated the effect of the ternary elements on the APB energy of the γ'phase and assumed a linear superposition of the effects of the addition of each ternary element when considering complex multi-component systems. As a result, the following equation was derived.

Here, x _Cr , x _Mo , x _W , x _Ta , x _Nb and x _Ti represent the atomic% concentrations of chromium, molybdenum, tungsten, tantalum, niobium and titanium in the γ'phase, respectively. The composition in the γ'phase is determined by phase equilibrium calculation.

The third merit index is density. The density ρ was calculated using a simple rule of the mixture and a correction factor. Where ρ _i is the density of a given element and x _i is the atomic fraction of the alloying element.

The fourth merit index is cost. A simple rule of mixture was applied to estimate the cost of each alloy. Here, the cost of each alloy, the mass fraction x _i of alloying elements was used multiplied by the raw material cost c _i of the current (2017) of the alloying elements.

This estimation assumes that the processing costs are the same for all alloys. That is, the product yield is not affected by the composition.

The fifth merit index is based on the exclusion of alloy candidates based on improper microstructures created based on susceptibility to the TCP phase. To do this, the d-orbital energy level of the alloying element (referred to as Md) is used to determine the total effective Md level according to the following equation.

Here, x _i represents the mole fraction of the element i contained in the alloy. The higher the value of Md, the higher the possibility of TCP formation.

The sixth merit index is the gamma prime solver temperature. Gamma prime solves are defined as the temperature at which the volume fraction of gamma prime tends to be zero. This is determined using thermodynamic calculations, as described above in the second step of the alloy design method. It is used to calculate the phase diagram and thermodynamic properties of a particular alloy composition and to discover the temperature at which the phase transition occurs.

The seventh merit index is the solid solution merit index. Solid solution curing occurs in a (FCC) matrix phase called gamma (γ), and this curing mechanism is particularly important at high temperatures due to its high strength and creep resistance. A model has been adopted that assumes the superposition of individual solute atoms for reinforcement of the matrix phase. _{The solid solubility strength coefficients k i} of the elements considered within the design area are 225, 39.4, 337, 1015, 1183, 1191, 775 for aluminum, cobalt, chromium, molybdenum, niobium, tantalum, titanium and tungsten, respectively. And 977 MPa / at.% ^1/2 (H. Roth, C. Davis, and R. Thomson: Metallurgical and Materials Transactions A, 1997, vol. 28, pp. 1329-1335). The solid solution index is calculated based on the equilibrium composition of the matrix phase using the following formula.

Here, M _{solid-solution} is a solid solution figure of merit, x _i is the concentration of the element i of the γ matrix phase.

The alloy composition of the present invention was identified using the ABD method described above. The design intent of this alloy is to achieve significant improvements in strength, especially high temperature strength and creep resistance, in combination with low alloy costs, improved oxidation / corrosion resistance and microstructural stability. According to the new balance of alloy properties, the maximum operating temperature can be improved as compared with the prior art, especially in use for turbine disc applications where the operating temperature of the component is 800 degrees or higher.

Table 3 lists the material properties (determined using the ABD method) in the nominal composition of alloys (listed in Table 1) commonly applied / studied for powder metallurgy (PM) turbine disc applications. New alloy designs were considered in association with the predicted properties listed for these alloys. Table 3 shows the calculated phase ratios, inconsistencies and merit indices created by the "Alloy Design" software. This is the result for the nickel-based superalloys listed in Table 1.

The design principle of the new alloy will be described below.

The addition of aluminum, niobium, tantalum and titanium affects the proportion of precipitation-hardened phase γ'. The requirement that the strength merit index exceed 1900 MPa was selected. This requirement shows that the strength is improved compared to US8,147,749, which is the strongest of the prior arts listed. By plotting the strength merit index vs. volume fractions of all alloy compositions in the design area, it was found that the desired strength can be achieved by having a gamma prime volume fraction of 51% or more at a temperature of 850 ° C. (Fig. 2).

Figure 3 shows the ratio of alloy γ'(as contour lines) to the total of titanium, tantalum and niobium (based on the relationship of _{0.6W Ti} + 0.31W _{Nb + 0.15W Ta) vs. the plotted aluminum-based alloy.} The relationship with the composition is shown. The amount of titanium, niobium, and tantalum added is given a weighting factor for converting mass% to "aluminum equivalent". Tantalum is included in this analysis because the cost of the alloy can be very high and therefore the tolerable level of tantalum is very high. This makes it possible to directly compare the effects of elements with significantly different densities. For example, aluminum has ^{a density of 2.7 g / cm 3} , whereas titanium has ^{a density of 4.5 g / cm 3} , so a coefficient of 0.6 is applied (ie, 2.7 / 4). .5 = 0.6). Similar to titanium, a constant is added to convert the amount of niobium element (8.57 g / cm ³ ) and tantalum element (16.4 g / cm ^{3) added to "aluminum equivalent".} That is, the correction factors for niobium and tantalum are determined from the densities of those elements relative to aluminum and are 0.31 and 0.15, respectively. From FIG. 3, it can be seen that in order to realize an alloy in which the ratio of γ'is 51% or more, the addition amounts of aluminum, titanium and niobium must follow the following formula.

Here, f (γ') is a numerical value, and W _Ti , W _Nb , W _Ta, and W _Al are mass% of titanium, niobium, tantalum, and aluminum contained in the alloy, respectively. In order to maintain the easy ability to process the alloy, the gamma prime solver is preferably 1180 ° C. or lower, which means that it is beneficial to have a gamma prime ratio of 62% or less (FIG. 4). See below). In order for the gamma prime ratio to be 62% or less, the value of f (γ') must be 7.4 or less. Therefore, f (γ') is preferably in the range of 6.2 to 7.4. More preferably, the gamma prime solution of the alloy is 1170 ° C. or lower. This limits the gamma prime ratio to 56% or less. In order to realize this, f (γ') needs to be 6.7 or less.

The gamma prime volume fraction is measured experimentally by the following procedure. After prolonged exposure to heat of 850 ° C., the sample is quenched with water to cut out a portion of the material and polished using a scanning electron microscope using conventional / standard metallurgical preparation techniques. When the preparation is completed, the fine structure of gamma / gamma prime can be observed by a scanning electron microscope, and particles having a diameter of 30 nm or more can be observed. At least 10 images are taken that provide a statistically representative dataset. The image should cover an area of at least 1 mm ^2. It is necessary to process a two-dimensional image for clarifying the fine structure of gamma / gamma prime so as to identify the gamma prime phase, and calculate the area ratio of the gamma prime phase. The area fraction of the phase is considered the volume fraction of gamma prime and must be between 51 and 62%.

In order to achieve a good balance between strength and ability to process alloys, the γ'phase sorbus temperature is set to 1180 ° C. or lower. The γ'solvus is preferably 1180 ° C. or lower because it is possible to reduce the cracking susceptibility of the alloy during cooling from a temperature equal to or higher than the γ'solvus temperature while enabling heat treatment of γ'solvus or higher. By performing the heat treatment at a temperature equal to or higher than the γ'solvus temperature, coarse particles can be grown and the resistance to dwell fatigue can be improved. Therefore, it is desirable to perform the heat treatment at a temperature equal to or higher than the γ'solvus temperature. .. This damage mechanism is often a life limiting factor in this class of alloys. Based on FIG. 4, _{the relationship between the alloy} γ'solvus and the total of titanium, tantalum and niobium (based on the relationship of _{0.6W Ti} + 0.31W Nb + 0.15W _{Ta) and the alloy composition based on aluminum is obtained.} Was done. The amount of aluminum, titanium and niobium added is according to the following formula.

Here, f (solvus) is a numerical value. In order to produce an alloy in which Sorbas is 1180 ° C or lower, the value of f (solvus) needs to be less than 8.0. According to this constraint, the gamma prime volume fraction is limited to 62% (see FIG. 3). In order to produce an alloy having a sorbus of 1170 ° C. or lower, the value of f (solvus) is preferably less than 7.3. When the sorbus is 1170 ° C. or lower, the ability to process alloys can be further improved. Therefore, it is preferable to limit the proportion of gamma prime to 56% (see FIG. 3).

Relationship with 1.0 ≤ (0.6W _Ti + _{0.31W Nb} + 0.15W _Ta ) / W _Al ≤ 1.3 (DJ Crudden, N. Warnken, A. Mottura, and RC Reed. Modeling of the influence of alloy composition on flow stress in high-strength nickel-based superalloys. Acta Materialia, 7: 356-370, 2014) It is beneficial to select an alloy with a proportion of elements that satisfies it. The minimum value is preferably limited to 1.0. As a result, the APB energy is significantly increased, so that the alloy strength can be increased (see equation (6)). Increasing the APB energy improves resistance to precipitation shear, especially in the intermediate temperature range of 600-850 ° C., which is the intended operating temperature range of the alloy, for tensile and creep strength. It is desirable because it can impart strength to the alloy from both perspectives. The maximum value is preferably limited to 1.3. This is necessary to maintain the stability of the γ'phase, above which the undesired eta phase (Ni ₃ Ti) and delta phase (Ni _{3) reduce the ductility and fatigue resistance of the alloy.} Nb) is likely to be formed. High concentrations of niobium _{stabilize the niobium-rich delta phase Ni 3} Nb, so niobium needs to be limited to 4.0% by weight or less. Alloys with a ratio of (0.6W _Ti + _{0.31W Nb + 0.15W Ta} ) / W _Al between 1.0 and 1.3 have the desired combination of strength and gamma prime stability. More preferably, the niobium contained in the alloy is 3% by mass or less. This is because, with respect to niobium, it has been found that the formation of niobium oxide increases the rate of dwell crack propagation in the alloy. Most preferably, the niobium contained in the alloy is limited to 2% by mass or less. This inhibits the formation of niobium oxides and further improves resistance to retention crack propagation.

FIG. 3 shows the relationship between the γ'ratio of the alloy and the total effect of aluminum, niobium element (based on the relationship with _{0.6W Ti} + _{0.31W Nb} + 0.15W _{Ta), titanium element and tantalum element.} show. This figure shows the relationship of gamma prime sorbas when f (solvus) is 8.0 and 7.3. Further, in this figure, _{the relationship when (0.6W Ti} + 0.31W _Nb + 0.31W _Ta ) / W _Al is 1.0 and 1.3 is drawn. The hatched regions in FIG. 3 indicate preferred composition regions in the present invention. From this figure, in order to make the gamma prime ratio 51% or more, the aluminum content needs to be 2.8% by mass or more (FIG. 3). In order to limit the gamma prime solution to 1180 ° C. or lower, the aluminum content must be limited to 3.7% by mass or less. The aluminum content is preferably limited to 3.5% by mass. This helps lower the gamma prime solver temperature. More preferably, the aluminum content is limited to 3.1% by mass. This makes the combination of intensity and lower gamma prime solver temperature even better.

FIGS. 5-9 show the effects of titanium, niobium and tantalum on the alloy strength from the viewpoint of the strength merit index when the aluminum concentration is limited to 2.8 to 3.7% by mass. Each figure shows the limitation of gamma prime sorbus (f (solvus) = 8.0) when the alloy contains the maximum amount of aluminum (3.7% by mass). From FIGS. 5-9, the relationship between the chemical properties of the alloy and the expected strength can be determined. When the aluminum content is 2.8 to 3.7% by mass, the amount of the element added is according to the following formula.

f (strength) is a numerical value that needs to be 4.2 or more in order to obtain an alloy having a strength merit index of 1900 MPa or more. By normalizing the effect of strength on titanium and considering these "aluminum equivalents", niobium and tantalum constants can be obtained based on Equation 5. For example, niobium has an aluminum equivalent of 0.31 and its effect on APB energy is 1.4 times that of titanium, so 0.44 (0.31 x 1.4) is applied as a coefficient. Since tantalum has an aluminum equivalent of 0.15 and its effect on APB energy is 1.8 times that of titanium, a coefficient of 0.27 (0.15 × 1.8) is applied.

From FIGS. 5 to 9, it can be seen that it is not easy to achieve a desired level of strength merit index (1900 MPa) while maintaining a preferable low sorbus temperature with niobium and titanium alone. Therefore, the alloy of the present invention needs to contain 2.4% by mass or more of tantalum. Higher levels of tantalum can increase strength and lower γ'solvus, but this is only possible at titanium and niobium levels, so the tantalum content in the alloy is 2.45% by weight. It is preferably more than or equal to 2.5% by mass or more. Most preferably, tantalum is 3.4% by mass or more. Even more preferably, the tantalum content in the alloy is 5.1% by weight or higher, especially when niobium is limited to 2.0% by weight. As a result, the alloy strength can be further increased and the strength merit index can be set to 1950 MPa or more. Preferably, niobium is present in at least 1.0% by weight to contribute to the strength of the alloy.

The titanium content of the alloy is limited to 5.1% by weight or less. As a result, an alloy having the correct balance between the strength (from the viewpoint of the strength merit index of 1900 MPa or more) and the production capacity (from the viewpoint of the gamma prime solver of 1180 ° C. or less) can be obtained (Fig. 5). By adding titanium to the alloy, the effect of improving the alloy strength can be obtained. On the other hand, since titanium may have an adverse effect on oxidation, titanium is preferably limited to 4.8% by mass (FIG. 6), and more preferably 4.6% by mass (FIG. 6). FIG. 7). This achieves an improved balance between strength and oxidation resistance. Even more preferably, especially when the tantalum content is 5.1% by weight, limiting the titanium content to 4.2% by weight provides a higher strength of 1950 MPa, as well as alloy strength and oxidation resistance. A better combination with sex is obtained.

Based on the maximum tantalum concentration of 9.5% by mass (from the viewpoint of alloy density described later using FIG. 11) and the maximum concentration of niobium (4% by mass), the content of titanium in the alloy. The amount is at least 0.3% by weight according to the relationship described in f (strength). The titanium content is at least 1.1% by weight, especially if niobium is limited to 3.0% by weight (to improve stability). More preferably, the titanium content is at least 1.8% by weight, especially if the niobium content is 2.0% by weight or less (to further improve stability). It is also desirable to limit the titanium content of the alloy based on its adverse effects on oxidation.

It is desirable to design alloys with a strong gamma matrix phase, along with an increase in strength contribution based on precipitation hardening due to the gamma prime phase (calculated in terms of strength merit index). The strength of the gamma matrix can be calculated from the viewpoint of the solid solution merit index. Solid solution strength is particularly important for imparting high temperature strength (both tensile strength and creep strength) to the alloy. Tungsten and molybdenum have large coefficients and are strongly distributed to the gamma phase. Unlike this, niobium and tantalum have a large intensity coefficient, but their distribution to the gamma phase is limited (see Equation 10). Therefore, the solid solution strength of the gamma phase of the alloy mainly depends on the amount of tungsten and molybdenum added. FIG. 10 shows the relationship between molybdenum, tungsten and the solid solution index. Since the density of tungsten is about twice that of molybdenum, a factor of 0.5 is applied to the tungsten content. That is, this coefficient explains the difference in density. It is desirable that the solid solution index be more than 100 MPa in order to realize a creep strength superior to that of the prior art (particularly the alloys shown in Table 3 having a strength merit index of more than 1800 MPa). From FIG. 10, the relationship between the amount of tungsten and molybdenum added and the solid solution index can be determined.

Here, f (solid solution) is a numerical value that requires 5.7 or more, and W _Mo and _WW are molybdenum and molybdenum in the alloy for realizing an alloy having a solid solution merit index of more than 100 MPa, respectively. Represents the mass% of tungsten. Due to the density ^{constraint of 8.6 g / cm 3} , tungsten is limited to 8.0% by weight, preferably 7.8% by weight, most preferably 6.9% by weight (this). Will be described in the next section with reference to FIG. 11). Therefore, based on the upper limit of tungsten (8.0% by weight), the alloy comprises a minimum of 1.1% by weight of molybdenum to meet the solid solution requirements. Molybdenum preferably exists in an amount of 1.2% by mass or more, especially when tungsten is limited to 8.2% by mass. Molybdenum is more preferably present in an amount of 1.7% by mass or more, especially when tungsten is limited to 6.9% by mass. It is desirable that f (solid solution) is 6.0 or more. As a result, the solid solution merit index can be set to 103 MPa or more.

In combination with the increase in alloy strength, it is useful to identify alloys that have a good combination of strength and mass. Therefore, it is desirable to control the density. That is, by limiting the density to 8.6 g / cm ³ or less as the design goal of this alloy, a density equivalent to that of the high-strength alloy in Table 3 can be obtained. FIG. 11 shows the effect of tantalum and tungsten on the alloy density. Since these alloying elements have a density significantly higher than that of nickel (8.9 g / cm ³ ), they have the greatest effect on the alloy density. The densities of tungsten and tantalum are 19.3 g / cm ³ and 16.4 g / cm ³ , respectively. From FIG. 11, the tantalum content of the present invention needs to be limited to 9.5% by mass or less in order to limit the density of the alloy. From FIG. 11, the relationship between the amount of tungsten and tantalum added and the alloy density can be determined. The amount of the element added follows the following formula.

Here, f (density) is a numerical value of 9.4 or less in order to achieve a density of ^{8.6 g / cm 3 or less.} Based on the desired minimum level of tantalum (> 2.4% by weight), it is desirable that the tungsten content be limited to 8.0% by weight. Preferably, tungsten is limited to 7.8% by weight or 6.9% by weight in order to keep the alloy density low. This allows tantalum to be contained at higher levels for increased strength. The tungsten content is preferably 3.3% by mass or more (this will be described later from the viewpoint of creep merit index and alloy cost). This limits the tantalum content to 6.4% by weight or less, ensuring a good balance of creep resistance, alloy cost and density.

The amount of cobalt and tantalum added has the strongest effect on alloy costs. FIG. 12 shows the relationship between the amount of tantalum and cobalt added and the alloy cost. Based on FIG. 1, it is judged that it is desirable to limit the alloy cost to 26 $ / kg because it is necessary to significantly increase the cost in order to further increase the strength. In addition, this reduces costs compared to the other high-strength alloys listed in Table 3. Therefore, the $ 26 / kg cost limit provides an attractive balance between alloy cost and performance. The cobalt concentration of the alloy is limited to 24.9% by weight based on the minimum amount of tantalum (> 2.4% by weight) contained in the alloy. The relationship between the chemical properties of the alloy and the predicted cost is as follows.

Here, f (cost) needs to be a numerical value of 14.1 or less in order to achieve a cost of 26 $ / kg or less. If the minimum amount of tantalum contained is 2.4% by weight, this results in a maximum cobalt concentration of 24.9% by weight. In order to increase the level of strength, the tantalum content is preferably 2.45% by mass or more or 2.5% by mass or more. Cobalt is preferably limited to 24.6% by weight. More preferably, tantalum is 3.4% by mass or more. It is more preferred to limit the cobalt to 22.8% by weight. Most preferably, tantalum is 5.1% by mass or more. Most preferably, cobalt is limited to 19.1% by weight. Even more preferably, the cost should be limited to $ 22 / kg and therefore f (cost) should be less than 10.3 and the cobalt concentration of the alloy should be limited to 16.8% by weight. .. In particular, when the tantalum concentration is 3.4% by mass or more, it is more preferable to limit the cobalt to 14.7% by mass. In particular, when the tantalum concentration is 5.1% by mass or more, cobalt is most preferably limited to 11.1% by mass.

The creep resistance from the viewpoint of the creep merit index depends on the amount of molybdenum, tungsten, and cobalt added (FIGS. 13 to 17). In order to impart sufficient creep resistance to the alloy, it is desirable ^{to set the target creep merit index to 2.8 × 10-16} m- ^{2 s.} Based on FIGS. 13 to 17, the relationship between the amounts of tungsten, cobalt and molybdenum added to the creep merit index can be determined. The amount of these elements added is according to the following formula.

Here, f (creep) needs to be a numerical value of 17.2 or more in order to realize an alloy having a creep merit index of ^{2.8 × 10-16} m- ^{2 s or more.} Included in the alloy to achieve a creep merit index of ^{2.8 x 10-16} m- ² s or higher, based on the upper limit of molybdenum (4.4% by weight) and the upper limit of tungsten (8.0% by weight). Cobalt should be at least 5.9% by weight. Tungsten is preferably limited to 7.8% by mass. In this case, cobalt is preferably at least 6.1% by weight, which is desirable in any case as it increases creep strength. Tungsten is more preferably limited to 6.9% by mass. In this case, it is more preferable that the cobalt concentration is 7.1% by mass. As described in relation to alloy costs, it is most preferred to reduce the use of cobalt in the alloy, preferably to 11.1% by weight or less. The tungsten content is preferably at least 3.2% by mass.

Figures 18-23 show the effect of chromium, tungsten and molybdenum on the stability number. The higher the stability number, the easier the alloy to form the TCP phase. Since the TCP phase leads to deterioration of material properties, it is beneficial to limit or stop the precipitation of TCP phase formation. In order to obtain a good level of oxidation resistance, it is desirable that the chromium level is 9.0% by mass or more. This level of chromium can form a protective chromium oxidation scale. With reference to the conventional alloys shown in Table 3, the target stability is 0.92 or less in order to avoid TCP formation while ensuring microstructural stability. In order to avoid TCP formation while ensuring better microstructural stability, the target stability is preferably 0.91 or less. Based on FIGS. 18 to 23, it was found that the addition amounts of the molybdenum element, the tungsten element and the chromium element follow the following formulas.

Here, f (stability) needs to be a value of 30.2 or less in order to realize an alloy having a stability number of 0.92 or less. Considering that the formula of solid solution strength is f (solid solution)> 5.7, it can be seen that tungsten does not have to be present when the upper limit of the molybdenum content is set to 4.4% by mass. Therefore, the upper limit of the molybdenum content is 4.4% by mass. By limiting the molybdenum content to 4.4% by mass, the chromium content can be maximized while satisfying the stability requirement, resulting in an excellent balance between high temperature strength (obtained from solid solution strength) and oxidation resistance. Can be obtained. Therefore, based on the maximum molybdenum content of 4.4% by weight, the chromium content is limited to 13.2%, which allows a good balance between high temperature strength and oxidation resistance.

The stability number is preferably limited to 0.91. In order to do this, the value of f (stability) needs to be 28.3 or less. Therefore, it is preferable to limit the chromium content to 11.9% by mass. This limits the stability number to 0.91 and provides better microstructural stability based on the molybdenum and tungsten content described above. More preferably, the chromium content is limited to 11.5% by weight. As a result, the stability number is 0.92 or less, so that the optimum balance between high temperature strength, cost and stability can be obtained. Even more preferably, the chromium content is limited to 11.2% by weight. Thereby, the number of Md can be limited to 0.91.

Addition of carbon, boron and zirconium is required to give strength to the grain boundaries. This is particularly beneficial for the creep and fatigue properties of the alloy. Carbon is added to function as grain boundary pinning particles. Carbon is required when the heat treatment is performed at a temperature above the gamma prime sorbus temperature in order to suppress excessive particle growth. The carbon concentration should be in the range of 0.01% by mass to 0.1% by mass. The carbon level is preferably between 0.2 and 0.06 in order to better distribute the microstructure of the alloy, especially the carbide phase for controlling the particle size.

The boron concentration should be in the range of 0.001 to 0.1% by weight. By adding boron, creep ductility and grain boundary strength can be improved through the formation of a boride phase. The boron content in the alloy is preferably 0.01-0.05% by mass in order to bring the boride phase to the desired level.

The zirconium concentration should be in the range of 0.001% by mass to 0.3% by mass, preferably 0.02 to 0.1% by mass. Zirconium serves to expel unwanted impurities (eg, oxygen and sulfur) contained in the alloy. These impurities can cause embrittlement of the alloy, especially due to grain boundary embrittlement.

When the alloy is manufactured, it is beneficial that the alloy is substantially free of unavoidable impurities. These impurities may include sulfur element (S), manganese element (Mn) and copper element (Cu). Sulfur elements should be lower than 0.003% by weight (30PPM in terms of mass). Manganese is an unavoidable impurity limited to 0.25% by weight, preferably less than 0.1% by weight. Copper (Cu) is an unavoidable impurity, preferably limited to 0.5% by weight. The presence of sulfur in excess of 0.003% by weight can cause embrittlement of the alloy, and sulfur segregates at the alloy / oxide interface formed during oxidation. Therefore, the sulfur level is preferably less than 0.001% by weight. Vanadium, which is an unavoidable impurity, adversely affects the oxidizing behavior of the alloy, and is therefore preferably limited to 0.5% by mass, preferably less than 0.3% by mass, and most preferably less than 0.1% by mass. Will be done. This segregation can lead to increased disruption of the protective oxide scale. If the concentration of these unavoidable impurities exceeds the specified level, problems with product yield and deterioration of the material properties of the alloy are expected.

It is beneficial to add hafnium (Hf) up to 0.5% by weight in order to constrain unavoidable impurities in the alloy and to impart strength. Since hafnium is a strong carbide forming material, it can bring about further strengthening of grain boundaries. Hafnium is preferably limited to 0.2% by mass, more preferably less than 0.1% by mass, because the element cost is high and its addition adversely affects the alloy cost.

So-called "reactive elements" (yttrium (Y), lanthanum (La) and cerium (Ce)) are added at levels up to 0.1% by weight. This is beneficial for improving the adhesiveness of the protective oxide layer such as _{Cr 2} O _3. These reactive elements can "clean up" harmful elements such as sulfur. Sulfur segregates at the alloy oxide interface, weakening the bond between the oxide and the substrate, resulting in oxide exfoliation. It may be beneficial to add silicon (Si) up to 0.5% by weight. The addition of silicon at levels up to 0.5% by weight to nickel-based superalloys has been shown to be beneficial for oxidizing properties. In particular, silicon segregates at the alloy / oxide interface and improves the bondability of the oxide to the substrate. As a result, peeling of the oxide is suppressed, and as a result, the oxidation resistance is improved.

In one embodiment of the invention, it is desirable to include iron instead of nickel. This has the advantage that the cost of the alloy can be reduced and the recycling capacity of the alloy can be increased. The addition of iron can impair microstructural stability. By limiting the level of iron addition to 4.0% by weight, a good balance between low cost, improved recyclability and microstructural stability can be obtained. More preferably, it is in the range of 1.0% by mass to 2.0% by mass.

Based on the description of the invention in this section, the broad scope of the invention is listed in Table 4. Further, Table 4 shows a preferable range. Table 4 shows the composition range of the new design alloy in% by mass.

The next section describes exemplary compositions of the invention. The calculated properties of these new alloys are listed. The rationale for the design of these alloys will be described below.

Two examples of the present invention are shown in Table 5. The expected properties of the alloy are listed in Table 6. The listed alloys have the advantage of improved strength over the prior art alloys listed in Table 3 in terms of strength merit index. This strength improvement is achieved in combination with the same sorbus temperature as in the prior art to enable the production of alloys. The density of the alloys in Table 5 is also equivalent to that of the alloys in Table 3 having a strength index of 1700 MPa or more. These improvements in material performance are achieved while maintaining costs equal to or less than those of alloys with a strength index of 1700 MPa or higher. Table 5 is an example of the alloy of the present invention. Table 6 shows the calculated phase fractions and merit indexes created by the "Alloy Design" software. Table 6 shows the results of the compositions listed in Table 5.

In Table 7, the amounts of gamma prime forming elements in the alloy ABD-PMD4 are changed. Since the alloys ABD-PMD5 to ABD-PMD8 have low levels of gamma prime forming elements, the strength of the alloy decreases due to the decrease in the gamma prime volume fraction (Table 8). However, higher strength than the prior art in Table 3 is still achieved. Reducing gamma prime forming elements has the advantage of reducing gamma prime solvers, which improves the ability to form alloys through thermomechanical treatment. Also, lowering the sorbus makes the alloy less susceptible to cracking during heat treatment. Alloy Examples ABD-PMD10 has higher levels of gamma prime forming elements as compared to ABD-PMD4. It can be seen that the intensity can be further increased while maintaining the gamma prime sorbus below 1180 ° C. This alloy has higher mechanical strength than ABD-PMD4 while maintaining thermomechanical properties, but does not completely achieve the preferred gamma prime solution (less than 1170 ° C.). Table 7 shows an exemplary composition in which the content of the gamma prime forming element of the exemplary alloy ABD-PMD4 was altered to alter the gamma prime content and the gamma prime solves. Table 8 shows the calculated phase fractions and merit indexes created by the "Alloy Design" software for alloys with varying gamma prime forming element content in the exemplary alloy ABD-PMD4. This is the result of the compositions listed in Table 7.

In Table 9, _{the values of 0.6W Ti} + 0.15W _Ta are kept constant, and titanium and tantalum are changed. The alloys ABD-PMD11 to PMD13 have a lower tantalum content than PMD-4, and titanium is used instead of tantalum. This is especially advantageous when the elemental cost of the alloy needs to be reduced. In the alloys PMD-14 to PMD-16, tantalum is used instead of titanium. This is advantageous because it further increases the strength of the alloy and lowers the gamma prime solution to improve the ability to produce the alloy. Titanium reduction also helps improve oxidation resistance, but these improvements are accompanied by increased alloy costs. Table 9 shows a composition example in which the titanium element and the tantalum element of the exemplary alloy ABD-PMD4 are replaced at the same ratio. Table 10 shows the calculated phase fractions and merit indices created by the "Alloy Design" software for alloys in which the titanium and tantalum elements of the exemplary alloy ABD-PMD4 are replaced at the same ratio. This is the result of the compositions listed in Table 9.

In Table 11, _{the values of 0.6W Ti} + 0.31W _Nb are kept constant, and titanium and niobium are changed. The alloys ABD-PMD17 to PMD20 have a lower niobium content than PMD-4, and titanium is used instead of niobium. This is especially advantageous when the niobium content in the alloy needs to be reduced. This is because reducing niobium can reduce susceptibility to the formation of niobium oxide. Here, niobium oxide can promote oxidation that promotes the cracking mechanism of nickel superalloys. In the alloys PMD-21 to PMD-24, niobium is used instead of titanium. This is advantageous because it further increases the strength of the alloy and lowers the gamma prime solution to improve the ability to produce the alloy. Titanium reduction also helps improve oxidation resistance, but these improvements are accompanied by increased alloy costs. Table 11 shows a composition example in which the titanium element and the niobium element of the exemplary alloy ABD-PMD4 are replaced at the same ratio. Table 12 shows the calculated phase fractions and merit indices created by the "Alloy Design" software for alloys in which the titanium and niobium elements of the exemplary alloy ABD-PMD4 are replaced at the same ratio. This is the result of the compositions listed in Table 11.

In Table 13, the tungsten level of the alloy ABD-PMD4 is increased to improve the creep merit index and the creep resistance of the alloy is improved. The molybdenum level of the alloy is controlled to maintain the stability and solid solution strength of the alloy. Tantalum and titanium have been substituted to maintain high alloy strength and low alloy density. Reducing tantalum also has the advantage of reducing alloy costs. Table 13 shows a composition example in which the molybdenum element and the tungsten element of the exemplary alloy ABD-PMD4 are replaced at the same ratio. Table 14 shows the calculated phase fractions and merit indices created by the "Alloy Design" software for alloys in which the molybdenum and tungsten elements of the exemplary alloy ABD-PMD4 are replaced at the same ratio. This is the result of the compositions listed in Table 13.

In Table 15, the levels of molybdenum and tungsten are lowered and replaced with chromium in order to improve the creep resistance of the alloy. By increasing the cobalt level of the alloy, a high creep merit index is maintained and good creep resistance is obtained. Table 15 shows a composition example in which the molybdenum element and the tungsten element of the exemplary alloy ABD-PMD4 are reduced and the content of the chromium element is increased. Table 16 shows the calculated phase fractions and benefits created by the Alloy Design software for alloys with reduced molybdenum and tungsten elements and increased chromium element content in the exemplary alloy ABD-PMD4. Shows the index. This is the result of the compositions listed in Table 15.

Claims (25)

By mass%, 9.0 to 13.2% chromium, 5.9 to 24.9% cobalt, 0.0 to 4.0% iron, 1.1 to 4.4% molybdenum, 0. 0-8.0% tungsten, 2.8-3.7% aluminum, 0.3-5.1% tantalum, 0.0-4.0% niobium, over 2.4% 9.5 % Or less tantalum, 0.01-0.1% carbon, 0.001-0.1% molybdenum, 0.001-0.3% zirconium, 0.0-0.5% silicon, 0 .0 to 0.1% molybdenum, 0.0 to 0.1% tantalum, 0.0 to 0.1% cerium, 0.0 to 0.003% sulfur, 0.0 to 0.25 With% manganese, 0.0-0.5% vanadium, 0.0-0.5% copper, and 0.0-0.5% hafnium, the balance is nickel and unavoidable impurities. A nickel-based alloy composition satisfying the following formula, where the mass% of molybdenum, tungsten, niobium, tantalum, and titanium contained in the alloy are W _Mo , W _W , W _Nb , W _Ta, and W _{Ti, respectively.}
1.29W _Mo + 0.5W _W ≧ 5.7
0.6W _Ti + 0.44W _Nb + 0.27W _Ta ≧ 4.2 The nickel-based alloy composition according to claim 1, wherein the mass% of niobium, tantalum, titanium and aluminum contained in the alloy are W _Nb , W _Ta , W _Ti and W _{Al, respectively, and the following formula is satisfied.}
6.2 ≤ 0.6W _Ti + _{0.31W Nb} + 0.15W _Ta + 0.94W _Al ≤ 7.4
Preferably,
6.2 ≤ 0.6W _Ti + _{0.31W Nb} + 0.15W _Ta + 0.94W _Al ≤ 6.7 The nickel-based alloy composition according to claim 1 or 2, where the mass% of niobium, tantalum, titanium and aluminum contained in the alloy are W _Nb , W _Ta , W _Ti and W _{Al, respectively, and the following formula is satisfied.}
1.0 ≤ (0.6W _Ti + _{0.31W Nb} + 0.15W _Ta ) / W _Al ≤ 1.3 The nickel-based alloy composition according to any one of claims 1 to 3, wherein the mass% of tungsten and molybdenum contained in the alloy are W _W and W _{Mo, respectively, and the following formula is satisfied.}
6.0 ≤ 1.29 _{W Mo} + 0.5 _{W W} Weight percent tantalum and tungsten contained in the alloy, respectively W _Ta, When W _W, satisfying the following equation, nickel-based alloy composition according to any one of claims 1 to 4.
W _Ta + 0.88 _{W W} ≤ 9.4 The nickel-based alloy composition according to any one of claims 1 to 5, wherein the mass% of tantalum and cobalt contained in the alloy are W _Ta and W _{Co, respectively, and the following formula is satisfied.}
W _Ta + 0.47 _{W Co} ≤ 14.1 Tungsten contained in the alloy, the weight percent chromium and molybdenum, respectively W _W, when the W _Cr and W _Mo, satisfy the following equation, nickel-based alloy composition according to any one of claims 1 to 6.
_{W W + 1.62W Cr + 2.0W Mo} ≦ 30.2
Preferably,
_{W W + 1.62W Cr + 2.0W Mo} ≦ 28.3 The nickel-based alloy composition according to any one of claims 1 to 7, further comprising aluminum in an amount of 3.5% or less, preferably 3.1% or less in mass%. Any one of claims 1 to 8 comprising tantalum in mass% of 2.45% or more, preferably 2.5% or more, more preferably 3.4% or more, still more preferably 5.1% or more. The nickel-based alloy composition according to the item. The nickel-based alloy composition according to any one of claims 1 to 9, which comprises 6.4% or less of tantalum in mass%. The nickel-based alloy composition according to any one of claims 1 to 10, which comprises 1.0% or more of niobium in mass%. The nickel-based alloy composition according to any one of claims 1 to 11, wherein niobium is contained in an amount of 3.0% or less, preferably 2.0% or less in mass%. The nickel-based alloy composition according to any one of claims 1 to 12, comprising titanium in an amount of 1.1% or more, preferably 1.8% or more in mass%. The nickel-based alloy composition according to any one of claims 1 to 13, which comprises 4.8% or less, preferably 4.6% or less, more preferably 4.2% or less of titanium in terms of mass%. The nickel-based alloy composition according to any one of claims 1 to 14, which comprises 3.2% or more of tungsten in terms of mass%. The nickel-based alloy composition according to any one of claims 1 to 15, comprising tungsten in an amount of 7.8% or less, preferably 6.9% or less in mass%. The nickel-based alloy composition according to any one of claims 1 to 16, which comprises 1.2% or more, preferably 1.7% or more of molybdenum in mass%. The nickel-based alloy composition according to any one of claims 1 to 17, which comprises 6.1% or more, preferably 7.1% or more of cobalt in mass%. Cobalt, in mass%, 24.6% or less, preferably 22.8% or less, more preferably 19.1% or less, further 16.8% or less or 16.6% or less, still more preferably 14. The nickel-based alloy composition according to any one of claims 1 to 18, which comprises 7% or less, most preferably 11.1% or less. The nickel-based alloy composition according to any one of claims 1 to 19, which comprises 11.9% or less, preferably 11.5% or less, more preferably 11.2% or less of chromium in mass%. The nickel-based alloy composition according to any one of claims 1 to 20, comprising a gamma prime volume fraction of 51 to 62% at 850 ° C., preferably a gamma prime volume fraction of 51 to 56% at 850 ° C. .. The powder of the nickel-based alloy composition according to any one of claims 1 to 21. A turbine disc formed from the nickel-based alloy composition according to any one of claims 1 to 21 or the powder according to claim 22. A gas turbine engine comprising the turbine disk according to claim 23. A method of manufacturing a turbine disk, comprising compressing the powder according to claim 22, prior to casting.

Images