A high-temperature alloy compensation design method based on interaction characteristics of impurity element S and noble metal Ru

Abstract

The present application relates to the field of high-temperature alloy component design, in particular to a high-temperature alloy compensation design method based on the interaction characteristics of impurity element S and noble metal Ru. Single crystal high-temperature alloy is prepared by directional solidification, the total content of refractory elements (Cr, W, Mo, Re, Ta, Hf, etc.) in the high-temperature alloy is more than 20wt.%, the alloy does not contain rare noble metal Ru, etc., the high-temperature creep resistance of the alloy is improved through solid solution strengthening and precipitation strengthening, and the S content in the alloy is less than 1ppm, the TCP phase precipitation tendency is obviously reduced, and the number of TCP precipitated by thermal exposure is the least. Based on the interaction characteristics of S and Ru, the Ru for improving the stability of the alloy organization in the high-generation single crystal high-temperature alloy is removed, the S content in the alloy is controlled to be less than 1ppm to compensate the design of the alloy, so as to improve the stability of the single crystal high-temperature alloy organization, and the present application can provide a guiding ideology for the component design of low-cost high-generation single crystal high-temperature alloy.

Description

TECHNICAL FIELD

[0001] The application relates to the field of high-temperature alloy component design, and particularly relates to a high-temperature alloy compensation design method based on the interaction characteristics of impurity element S and noble metal Ru. BACKGROUND

[0002] In recent years, with the continuous increase of the thrust-to-weight ratio of an aero-engine, the working temperature of a turbine blade is higher and higher, which puts forward higher requirements on the temperature resistance of a high-temperature alloy. From the perspective of alloy design, the main way to improve the temperature resistance of a cast high-temperature alloy is to continuously increase the alloying degree. The total content of refractory elements in the fifth-generation single-crystal high-temperature alloy developed by a foreign unit reaches 26 wt.%, and high alloying is still the development trend of the cast high-temperature alloy. However, the increase of the alloying degree also affects the organizational stability of the cast high-temperature alloy, and the tendency of precipitating topologically close-packed (TCP) phases increases. Therefore, under the premise of obtaining more excellent high-temperature strength as the main target, effectively inhibiting the precipitation of TCP phases in the alloy has become an important problem in the development of advanced cast high-temperature alloys. By adding a ruthenium (Ru) element in the single-crystal high-temperature alloy, the precipitation of TCP phases in the single-crystal high-temperature alloy can be significantly inhibited, and on this basis, the fourth-generation single-crystal high-temperature alloy (such as TMS-138 with a Ru content of 2 wt.%) and the fifth-generation single-crystal high-temperature alloy (such as TMS-162 with a Ru content of 6 wt.%) are developed. However, Ru is a rare and precious metal, and its addition as an alloy element to the high-temperature alloy greatly increases the alloy cost. Compared with the typical third-generation single-crystal high-temperature alloy René N6 (without Ru), the cost of the fifth-generation single-crystal high-temperature alloy TMS162 (with a Ru content of 6 wt.%) is increased by about 6 times, and the sharp increase in cost limits the industrialized application of the high-generation single-crystal high-temperature alloy.

[0003] The patent with publication number CN118389908A proposes a low-cost single crystal superalloy with consideration of both organizational stability and performance, and a preparation method. Although the S content is controlled to be below 1 ppm, only the independent influence of S on organizational stability is considered, and the interaction mechanism of S replacing Ru is not proposed. The patent with publication number CN115044805A proposes a nickel-based single crystal superalloy with multiple performance balances and a preparation method. By adjusting elements such as Al, Cr, and Re, the nickel-based single crystal superalloy achieves multiple performance balances. However, the alloy does not contain Ru and Co elements, and the influence of S element on the organizational stability of the alloy is not mentioned, which cannot solve the TCP phase precipitation problem caused by the increase of high-refractory elements (W, Mo, and Ta) and cannot balance the high temperature capacity and organizational stability. The patent with publication number CN117321230A proposes an alloy, a powder, a method, and a component. The alloy is strengthened by high Ti and Mo content, and does not contain Re and Ru. However, the S content is not strictly controlled, and the TCP phase precipitation problem caused by high-refractory elements cannot be solved. The patent with publication number CN117295612A proposes an alloy, a powder, a method, and a component. By designing a composition system without Re and Ru, the performance is balanced by using elements such as Cr and Co. However, the S content is not strictly controlled, and the total content of refractory elements (W, Mo, and Ta) is low (<6 wt.%), which cannot meet the demand of high-generation single crystal superalloy for high-temperature strength.

[0004] Currently, the design of single crystal superalloy is based on the absolute purity assumption, ignoring the inherently existing impurity elements. S element is a recognized impurity element in cast superalloy, and reducing the content of S element can significantly improve the oxidation resistance, corrosion resistance, and organizational stability of the alloy. Therefore, it is urgent to develop a low-cost and high-organizational stability single crystal superalloy design method. SUMMARY

[0005] The purpose of the present application is to provide a high-temperature alloy compensation design method based on the interaction characteristics of impurity element S and noble metal Ru, to remove the rare noble metal Ru in high-generation (such as fourth-generation and fifth-generation) single crystal superalloy, to control the TCP phase precipitation tendency of the alloy by controlling the content of impurity element S in the alloy to be less than 1 ppm, and to ensure the mechanical properties of the single crystal superalloy.

[0006] In order to achieve the above purpose, the present application mainly provides the following technical scheme:

[0007] A high-temperature alloy compensation design method based on the interaction characteristics of impurity element S and noble metal Ru, comprising the following steps:

[0008] 1) Adjust the content of refractory elements used for solid solution strengthening and precipitation strengthening in the high-temperature alloy to more than 20wt.%, ensure the high-temperature mechanical properties of the high-temperature alloy through solid solution strengthening and precipitation strengthening, and calculate the topological close-packed phase precipitation tendency by the number of electron vacancies, on this basis, adjust the content of Ru and S in the alloy, and design high-temperature alloys with different compositions;

[0009] 2) According to the designed composition of the high-temperature alloy, high-temperature alloy master alloys with different Ru and S contents are prepared;

[0010] 3) High-temperature alloy test bars are prepared by using directional solidification process, and post-processing process including solid solution treatment and aging treatment is designed according to the content of refractory elements in the alloy;

[0011] 4) High-temperature thermal exposure test is carried out on the high-temperature alloy test bars, the number of TCP phases in high-temperature alloys with different Ru and S contents is observed, and the TCP phase precipitation tendency of high-temperature alloys with different Ru and S contents is analyzed; wherein, the TCP phase precipitation tendency of the high-temperature alloy with S content less than 1ppm and without Ru is significantly reduced, and the number of TCP phases precipitated in the alloy under the same thermal exposure condition is the least.

[0012] The high-temperature alloy compensation design method based on the interaction characteristics of impurity element S and noble metal Ru has the following composition and content by weight: refractory elements Cr 0-10wt.%, W 5-15wt.%, Mo 0-5wt.%, Re 0-8wt.%, Ta 0-10wt.%, Hf 0-3wt.%, the total content of the above refractory elements is more than 20wt.%; Al 2-8wt.%, Co 0-15wt.%, Ti 0-5wt.%, C 0-0.2wt.%, B 0-0.1wt.%, and the rest is Ni.

[0013] In step 1) of the high-temperature alloy compensation design method based on the interaction characteristics of impurity element S and noble metal Ru, the TCP phase precipitation tendency in the structure is judged according to the high-temperature alloy electron vacancy number calculation method.

[0014] In step 3) of the high-temperature alloy compensation design method based on the interaction characteristics of impurity element S and noble metal Ru, the directional solidification process selects high-speed solidification manufacturing process.

[0015] In step 3) of the high-temperature alloy compensation design method based on the interaction characteristics of impurity element S and noble metal Ru, the post-processing process is step-by-step heat treatment, the solid solution treatment process is optimized according to the content of refractory elements in the alloy, and the aging treatment process is optimized according to the content of γ' phase forming elements in the alloy.

[0016] In step 4), after heat exposure, scanning electron microscopy observation is performed, the area percentage of TCP phase in alloys with different Ru and S contents is analyzed and counted, so as to judge the microstructure stability of the alloys with different Ru and S contents.

[0017] Compared with the prior art, the high-temperature alloy compensation design method based on the interaction characteristics of impurity element S and noble metal Ru has at least the following beneficial effects:

[0018] 1. From the perspective of improving the high-temperature mechanical properties of single crystal high-temperature alloys, the content of solid solution strengthening and precipitation strengthening of refractory elements in the single crystal high-temperature alloy is optimized, so that the total content exceeds 20wt.%, and multiple groups of single crystal high-temperature alloy compositions with different refractory element contents are selected to ensure high-temperature mechanical properties. In particular, the content of impurity element S in the alloy is controlled to be less than 1ppm, and the alloy does not contain rare noble metal Ru, the inhibitory effect of S content <1ppm on TCP phase precipitation is fully utilized to completely replace Ru, the impurity control of S and the function replacement of Ru are combined, and the contradiction between TCP phase inhibition and cost in the high-refractory element system is solved. Further, the single crystal high-temperature alloy test rod is prepared by using directional solidification process, and then step-by-step heat treatment is performed. After high-temperature heat exposure, the TCP phase in the alloy microstructure is significantly reduced, and the high-temperature mechanical properties of the single crystal high-temperature alloy are ensured.

[0019] 2. The design method proposed in the embodiment verifies the TCP phase precipitation tendency through electron vacancy number calculation and high-temperature heat exposure test. After 1100℃ heat exposure for 1000h, it is found that a large amount of TCP phase is precipitated in the microstructure of the traditional single crystal high-temperature alloy after high-temperature heat exposure, and the amount of TCP phase precipitated in the microstructure of the single crystal high-temperature alloy after heat exposure is significantly reduced after adding rare noble metal Ru, which conforms to the design idea of high-generation single crystal high-temperature alloy. Further, by controlling the S content (less than 1ppm) in the single crystal high-temperature alloy and not adding Ru element, only a small amount of TCP phase is precipitated in the microstructure of the alloy after heat exposure under the same conditions, and the amount is less than that of the single crystal high-temperature alloy containing Ru, and the microstructure stability of the alloy is effectively guaranteed, which provides a guiding idea for the research and development of high-performance single crystal high-temperature alloy.

[0020] The above description is only a summary of the technical scheme of the present application. In order to more clearly understand the technical means of the present application and can be implemented according to the content of the specification, the following will be described in detail with the preferred embodiments of the present application and with the help of the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 The figure shows the relationship between the refractory element content in the high-temperature alloy and the heat resistance of the alloy and the TCP phase precipitation tendency during heat exposure.

[0022] Figure 2 Microstructure of single crystal superalloys with different Ru and S contents after stepwise heat treatment in the examples. (a) Microstructure of conventional single crystal superalloys at different magnifications, (b) Microstructure of single crystal superalloys with Ru addition at different magnifications, (c) Microstructure of single crystal superalloys with controlled S at different magnifications.

[0023] Figure 3 Microstructure of single crystal superalloys with different Ru and S contents after 100 h heat exposure at 1100℃ in the examples. (a) Microstructure of conventional single crystal superalloys at different magnifications, (b) Microstructure of single crystal superalloys with Ru addition at different magnifications, (c) Microstructure of single crystal superalloys with controlled S at different magnifications.

[0024] Figure 4 Microstructure of single crystal superalloys with different Ru and S contents after 1000 h heat exposure at 1100℃ in the examples. (a) Microstructure of conventional single crystal superalloys at different magnifications, (b) Microstructure of single crystal superalloys with Ru addition at different magnifications, (c) Microstructure of single crystal superalloys with controlled S at different magnifications.

[0025] Figure 5 TCP phase area fraction in the microstructure of single crystal superalloys with different Ru and S contents after heat exposure at 1100℃ for different times in the examples. In the figure, the horizontal axis Exposure time is the heat exposure time (h), and the vertical axis Area fraction is the area fraction (%). DETAILED DESCRIPTION

[0026] The design idea of the present application is as follows:

[0027] As Figure 1As shown, the content of refractory elements in single crystal superalloy is crucial to the high temperature mechanical properties of the alloy. Generally speaking, the more the content of refractory elements, the higher the temperature resistance of the alloy. The content of refractory elements in the first generation single crystal superalloy is about 14wt.%, and the temperature resistance is about 1010℃ (137MPa / 1000h). The content of refractory elements in the second generation single crystal superalloy is increased to 17wt.%, and the temperature resistance is increased to 1040℃. The content of refractory elements in the third generation single crystal superalloy is about 19wt.%, and the temperature resistance is about 1070℃. However, the tendency of TCP phase precipitation in the alloy after heat exposure is obviously increased. In order to inhibit the precipitation of TCP phase, 3wt.% Ru is added in the fourth generation single crystal superalloy developed recently, and the content of refractory elements in the alloy is about 22wt.%, and the temperature resistance of the alloy is about 1090℃. At present, the design of single crystal superalloy is based on the assumption of absolute purity, and the impurity elements are ignored. S element is a recognized impurity element in cast superalloy, and reducing the content of S element can significantly improve the oxidation resistance, corrosion resistance and microstructure stability of the alloy. Therefore, optimizing and adjusting the content of refractory elements in the alloy and controlling the content of impurity element S in the alloy are crucial to the temperature resistance of single crystal superalloy.

[0028] Based on the above design idea, the high temperature alloy compensation design method based on the interaction characteristics of impurity element S and noble metal Ru is as follows:

[0029] 1) Preliminary determination of alloy composition range: adjust the content of refractory elements for solid solution strengthening and precipitation strengthening in single crystal superalloy, judge the precipitation tendency of TCP phase in the microstructure by electron vacancy number (Nv) calculation method, and design single crystal superalloy composition with different content of refractory elements.

[0030] The present application is suitable for all single crystal superalloy systems. Generally speaking, the nickel-based single crystal superalloy system mainly includes: Cr 0~20wt%, Co 0~15wt%, W 0~20wt%, Mo 0~10wt%, Re 0~8wt%, Ru 0~6wt%, C 0~0.2wt%, B 0~0.2wt%, Hf 0~3wt%, Al 1~8wt%, Ti 0~5wt%, Ta 0~10wt%, and the balance is Ni. This step mainly adjusts the content of refractory elements such as W, Mo, Re and Ru under the determination of other elements, and calculates the corresponding electron vacancy number to judge the TCP phase precipitation tendency in the alloy.

[0031] Preferably, according to the single crystal superalloy composition design principle (alloy contains a certain amount of Al, Cr to meet the alloy oxidation resistance requirements, the volume fraction of γ' phase in single crystal superalloy is 60%~70%), the content of Al, Cr and other anti-oxidation corrosion elements in superalloy, the content of γ' phase forming elements A1, Ti and Ta, the content of grain boundary elements C, B, and the content of solid strengthening elements W, Mo, Co, Cr, Re are basically determined. On this basis, the content of Ru and S in single crystal superalloy is adjusted, and the alloy composition of specific embodiments is shown in Table 1.

[0032] 2) According to the designed single crystal superalloy composition with different refractory element contents, a single crystal superalloy master alloy is prepared by using a vacuum melting furnace; a single crystal superalloy test bar is prepared by using a directional solidification furnace; the single crystal superalloy test bar is subjected to step-by-step heat treatment to obtain a single crystal superalloy with uniform structure, Figure 2 The microstructure of the single crystal superalloy with different Ru and S contents in the example after step-by-step heat treatment is shown in the following table.

[0033] 3) High-temperature thermal exposure experiment is carried out on the single crystal superalloy, specifically, the service temperature of the single crystal superalloy is selected to be 1100℃, and the thermal exposure time is 50h, 100h, 300h, 500h and 1000h respectively.

[0034] 4) TCP phase precipitation tendency analysis

[0035] The samples subjected to thermal exposure for different times in step 3) are observed by scanning electron microscopy, Figure 3 The microstructure of the single crystal superalloy with different Ru and S contents in the example after thermal exposure at 1100℃ for 100h is shown in the following table. It can be seen that the traditional single crystal superalloy has poor microstructure stability, and TCP phase begins to precipitate in the microstructure after 100h thermal exposure, while the single crystal superalloy with added Ru element and controlled S content less than 1ppm does not show TCP phase precipitation. Figure 4 The microstructure of the single crystal superalloy with different Ru and S contents in the example after thermal exposure at 1100℃ for 1000h is shown in the following table. TCP phase precipitates in all three alloys, but the number of TCP phase in the alloy with controlled S content is the least, followed by the single crystal superalloy with added Ru, and the number of TCP phase in the traditional single crystal superalloy is the most.

[0036] Figure 5The TCP phase area fraction in the microstructure of different Ru, S content single crystal superalloys in the examples after thermal exposure at 1100℃ for different time is shown. With the increase of thermal exposure time (0-1000h), the TCP phase area fraction of the three alloys all shows an upward trend, but the growth rate and the final area fraction of different alloys are significantly different. The TCP phase area fraction of the traditional single crystal superalloy is close to 1.2% at 1000h, the TCP phase precipitation tendency is large, and the microstructure stability is poor. The Ru added alloy inhibits the TCP phase precipitation to a certain extent, but the inhibitory effect gradually weakens with time, and the TCP phase area fraction is about 0.55% at 1000h, which shows that Ru alone cannot completely solve the TCP phase continuous precipitation problem in the high refractory element system. The TCP phase area fraction of the S controlled alloy grows most slowly during the thermal exposure process, and is only about 0.3% at 1000h. It can be seen that the microstructure stability of the single crystal superalloy with controlled S content is the best during the whole thermal exposure process.

[0037] Table 1 Alloy composition and electron vacancy number in the examples (element content is wt.%, S content is ppm)

[0038] Cr Co W Mo Re Al Ti Ta Hf C Ru S Ni Nv Conventional single crystal 3.42 9.95 5.83 0.57 4.81 5.74 0.81 7.93 0.12 0.005 0 2.18 Balance 2.02 Add Ru 3.45 9.96 5.86 0.52 4.84 5.71 0.82 7.95 0.13 0.006 1.94 2.16 Balance 2.13 Control S 3.45 10.01 5.96 0.55 4.89 5.65 0.8 8.08 0.13 0.004 0 0.32 Balance 2.02

[0039] As can be seen from Table 1, the Nv values of the three groups of alloys are all in the range of 2.02-2.13, wherein: the traditional single crystal superalloy (containing S 2.18ppm, without Ru), Nv=2.02, and the TCP phase quantity is the most after high temperature thermal exposure. The Ru added alloy (containing S 2.16ppm, Ru 1.94wt.%), Nv=2.13, and the TCP phase quantity is significantly reduced, but still more than the "S controlled" alloy. The S controlled alloy (containing S 0.32ppm, without Ru), Nv=2.02, and the TCP phase quantity is the least, and less than the Ru added alloy. In the case of similar Cr, Co, W, Mo, Re, Al, Ti, Ta, Hf, C compositions, S has a replacement effect on Ru, and under similar Nv values, the TCP phase inhibition effect of the low S alloy is better than that of the Ru containing alloy, which shows that S can replace the function of Ru by hindering TCP phase nucleation and other mechanisms.

[0040] The implementation result shows that the nickel-based high-temperature alloy prepared by the directional solidification has the total content of high-temperature alloy refractory elements (Cr, W, Mo, Re, Ta, Hf and the like) being more than 20 wt.%, the alloy does not contain rare and precious metals such as Ru, the high-temperature creep resistance of the alloy is improved through solid solution strengthening and precipitation strengthening, the content of S in the alloy is less than 1 ppm, the function of Ru is replaced by using the inhibition effect of S content less than 1 ppm on TCP phase precipitation, the TCP phase can be effectively inhibited in the Ru-free and high-refractory element system, and the balance of low cost, high organizational stability and high temperature capacity is realized. Based on the interaction characteristics of S and Ru, the Ru for improving the organizational stability of the high-generation single crystal high-temperature alloy is removed, the alloy is compensated by controlling the content of S in the alloy to be less than 1 ppm, so as to improve the organizational stability of the single crystal high-temperature alloy, and a guiding ideology is provided for the composition design of the low-cost high-generation single crystal high-temperature alloy.

Claims

1. A high-temperature alloy compensation design method based on the interaction characteristics of impurity elements S and noble metals Ru, characterized in that, The method comprises the following steps: 1) adjusting the content of refractory elements in the high-temperature alloy for solid solution strengthening and precipitation strengthening, so that the content exceeds 20 wt.%, and ensuring the high-temperature mechanical properties of the high-temperature alloy through solid solution strengthening and precipitation strengthening, and calculating the topological close-packed phase precipitation tendency through the number of electron vacancies, on the basis of which the contents of Ru and S in the alloy are adjusted, and high-temperature alloys with different compositions are designed; 2) preparing high-temperature alloy master alloys with different Ru and S contents according to the designed compositions of the high-temperature alloy; 3) preparing high-temperature alloy test bars by using directional solidification process, and designing a post-treatment process including solid solution treatment and aging treatment according to the content of refractory elements in the alloy; 4) performing high-temperature thermal exposure test on the high-temperature alloy test bars, observing the number of TCP phases in the high-temperature alloys with different Ru and S contents, and analyzing the TCP phase precipitation tendency of the high-temperature alloys with different Ru and S contents; wherein the TCP phase precipitation tendency of the high-temperature alloy with S content less than 1 ppm and without Ru is significantly reduced, and the alloy has the least TCP phase precipitation under the same thermal exposure condition.

2. The high-temperature alloy compensation design method based on the interaction characteristics of impurity element S and noble metal Ru according to claim 1, characterized in that, The composition and content of the high-temperature alloy are as follows in terms of weight percentage: refractory elements Cr 0-10 wt.%, W 5-15 wt.%, Mo 0-5 wt.%, Re 0-8 wt.%, Ta 0-10 wt.%, Hf 0-3 wt.%, and the total content of the above refractory elements exceeds 20 wt.%; Al 2-8 wt.%, Co 0-15 wt.%, Ti 0-5 wt.%, C 0-0.2 wt.%, B 0-0.1 wt.%, and the rest is Ni.

3. The high-temperature alloy compensation design method based on the interaction characteristics of impurity element S and noble metal Ru according to claim 1, characterized in that, In step 1), the TCP phase precipitation tendency in the structure is determined according to the high-temperature alloy electron vacancy number calculation method.

4. The high-temperature alloy compensation design method based on the interaction characteristics of impurity element S and noble metal Ru according to claim 1, characterized in that, In step 3), the directional solidification process is selected as the high-speed solidification method.

5. The high-temperature alloy compensation design method based on the interaction characteristics of the impurity element S and the noble metal Ru according to claim 1, characterized in that, In step 3), the post-treatment process is a step-by-step heat treatment, and the solid solution treatment process is optimized according to the content of refractory elements in the alloy, and the aging treatment process is optimized according to the content of γ' phase forming elements in the alloy.

6. The high-temperature alloy compensation design method based on the interaction characteristics of impurity element S and noble metal Ru according to claim 1, characterized in that, In step 4), after thermal exposure, scanning electron microscopy is performed, the area percentage of TCP phases in the alloys with different Ru and S contents is analyzed and counted, and the microstructure stability of the alloys with different Ru and S contents is determined.

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