Method for formulating solution treatment system of nickel-based single crystal superalloy
By measuring the characteristic phase transition temperature of nickel-based single-crystal high-temperature alloy and predicting solid solution temperature, a solid solution treatment system for nickel-based single-crystal high-temperature alloy was formulated, which solved the problem of complex solid solution treatment process in the prior art and difficulty in taking into account the degree of uniformity and no initial melt holes, and achieved uniformization and performance improvement of the alloy.
Patent Information
- Application Number
- CN202411779608.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-05
- Publication Date
- 2025-04-15
AI Technical Summary
In the prior art, the solid solution treatment system of nickel-based single-crystal high-temperature alloys is complicated, and it is difficult to take into account the technical problems of high uniformity and no initial melting holes.
By measuring the characteristic phase transition temperature of the cast nickel-based single-crystal high-temperature alloy and predicting the solution temperature Tpredict, a solution treatment system was formulated: the nickel-based single-crystal high-temperature alloy was placed at T1 temperature, slowly heated to T2 temperature and kept warm, then slowly heated to T3 temperature, and finally cooled to room temperature. Among them, T1=Tγ′-T0, T2=Tpredict, T3=Tin-T0, T0=3~7℃.
The degree of uniformity of the alloy is improved and the formation of initial melting holes is avoided, the solid solution treatment process is simplified, and the alloy performance is improved.
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Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of heat treatment of high-performance nickel-based single crystal high-temperature alloys, and specifically relates to a method for formulating a solid solution treatment system for a nickel-based single crystal high-temperature alloy. Background Art
[0002] Nickel-based single crystal high-temperature alloys are widely used in key hot end components (high and low pressure turbine blades) of aircraft engines and ground gas turbines due to their excellent high temperature performance. The continuous development of my country's aerospace technology has put forward higher requirements for the core components of aircraft engines. As the inlet temperature of aircraft engine turbines continues to increase, nickel-based single crystal high-temperature alloys have developed from the first generation of single crystal alloys to the fourth generation of single crystal alloys, and the content of refractory elements in the alloys has also increased from 16% to 22%. Among them, the content of rare and precious Re elements in the third generation of single crystal alloys has increased to 3-6wt.%, and the content of rare and precious Re and Ru elements in the fourth generation of single crystal alloys has increased to 6wt.% and 3wt.%, respectively.
[0003] Adding a large amount of refractory elements can significantly improve the mechanical properties of the alloy, but it will inevitably increase the difficulty of alloy solution treatment, mainly including: (1) The diffusion coefficient of refractory elements is low, especially the addition of Re elements, which will significantly increase the difficulty of alloy homogenization; (2) The increase in the content of refractory elements will aggravate the segregation of dendrite elements, resulting in an increase in the content of eutectic between dendrites, which greatly increases the difficulty coefficient of alloy homogenization treatment; (3) The initial melting temperature of the alloy is reduced, while the dissolution temperature of γ′ is increased, resulting in a significant reduction in the heat treatment window. At present, conventional step-by-step solution treatment can obtain a well-homogenized structure after solution treatment by extending the high-temperature holding time. However, the conventional step-by-step heat-insulating solution treatment system is complicated and cumbersome, and high-temperature and long-time heat-insulating treatment is prone to introduce a large number of initial melting holes (initial melting holes are caused by the melting of the eutectic structure between dendrites).
[0004] Existing technology has proposed a solution treatment method for the third-generation nickel-based single crystal high-temperature alloy based on lowering the solution treatment temperature to avoid initial melting of the alloy, but this method is still based on the traditional step-by-step solution treatment system. The solution treatment process is complicated, and it is difficult to ensure the degree of homogenization of the alloy by simply lowering the alloy solution treatment temperature; there is also technology that has proposed a solution heat treatment method for reducing the content of solution voids in high-rhenium nickel-based single crystal high-temperature alloys. This technology proposes that the solution voids of the alloy can be reduced by carrying out a long-term low-temperature homogenization pretreatment, but this technology does not reduce the maximum solution treatment temperature and significantly prolongs the total solution heat treatment time of the alloy. Summary of the invention
[0005] Therefore, the present invention provides a method for formulating a solution treatment system for a nickel-based single crystal high-temperature alloy, which can solve the technical problems in the prior art that the solution treatment system has complex procedures and is difficult to achieve both a high degree of homogenization and the absence of initial melting holes.
[0006] In order to solve the above problems, the present invention provides a method for formulating a solution treatment system for a nickel-based single crystal high-temperature alloy, according to the characteristic phase transition temperature of the cast nickel-based single crystal high-temperature alloy and the predicted solution temperature T predict Formulate a solution treatment system; the solution treatment system is:
[0007] The nickel-based single crystal high-temperature alloy is placed at a temperature of T1, then heated to a temperature of T2 at a rate of 0.5 to 1°C / min, and subjected to heat preservation treatment; after the heat preservation treatment, the temperature is raised to a temperature of T3 at a rate of 0.5 to 1°C / 30min; and then cooled to room temperature;
[0008] Wherein, the nickel-based single crystal high temperature alloy includes the elements Re and Ta; the characteristic phase transition temperature includes the γ′ phase re-dissolution temperature T γ′ and initial melting temperature T in ;
[0009] T1=T γ′ -T0, T2 = T predict , T3=T in -T0; wherein, T0 = 3 ~ 7 ° C.
[0010] Furthermore, the heat preservation treatment time is 4 to 6 hours.
[0011] Furthermore, differential scanning calorimetry (DSC) was used to measure the characteristic phase transition temperature: the γ′ phase resolubility temperature T γ′ and initial melting temperature T in .
[0012] Furthermore, the predicted solution temperature T predict The determination includes the following steps:
[0013] Determine characteristic organizational parameters: Determine characteristic organizational parameters of the cast nickel-based single crystal high-temperature alloy, wherein the characteristic organizational parameters include a primary dendrite spacing l and a dendrite element segregation ratio δ0;
[0014] Determine the predicted solution temperature T predict :The primary dendrite spacing l and dendrite element segregation ratio δ0 are input into the DICTRA kinetic software to simulate the diffusion behavior of alloy elements in the dendrite trunk / interdendrite region at different solution temperatures; when the residual segregation ratio of the element meets the set conditions, the corresponding solution temperature is determined as the predicted solution temperature T predict .
[0015] Furthermore, in determining the predicted solution temperature T predict In the step, the setting conditions are: the residual segregation ratio of the element Re is less than 1.7, and the residual segregation ratio of the element Ta is greater than 0.85.
[0016] Furthermore, the nickel-based single crystal high-temperature alloy is a third generation nickel-based single crystal high-temperature alloy.
[0017] On the other hand, the present invention also provides a solution treatment method for a nickel-based single crystal high temperature alloy, wherein the nickel-based single crystal high temperature alloy is subjected to a solution treatment to obtain a nickel-based single crystal high temperature alloy after the solution treatment, wherein the solution treatment adopts the following solution treatment system:
[0018] The nickel-based single crystal high-temperature alloy is placed at a temperature of T1, then heated to a temperature of T2 at a rate of 0.5 to 1°C / min, and subjected to heat preservation treatment; after the heat preservation treatment, the temperature is raised to a temperature of T3 at a rate of 0.5 to 1°C / 30min; and then cooled to room temperature;
[0019] Wherein, the nickel-based single crystal high temperature alloy includes elements Re and Ta;
[0020] T1=T γ′ -T0, T2 = T predict , T3=T in -T0;T γ′ is the γ′ phase remelting temperature, T in is the initial melting temperature and T predict To predict the solution temperature; T0 = 3 ~ 7 ° C.
[0021] In another aspect, the present invention further provides a nickel-based single crystal high-temperature alloy after solid solution treatment, wherein in the nickel-based single crystal high-temperature alloy after solid solution treatment: the initial melting hole area fraction is <0.01%; and / or
[0022] The eutectic content is 0; and / or
[0023] The residual segregation ratio of the element Re is less than 1.4; the residual segregation ratio of the element Ta is greater than 0.9.
[0024] Furthermore, the nickel-based single crystal high-temperature alloy after the solid solution treatment is obtained by the above-mentioned solid solution treatment method.
[0025] The method for formulating a solution treatment system for a nickel-based single crystal high-temperature alloy provided by the present invention has the following beneficial effects:
[0026] 1. The present invention measures the characteristic phase transition temperature (γ′ phase re-dissolution temperature T γ′ and initial melting temperature T in ), and then the diffusion behavior of alloy elements in the dendrite trunk / interdendritic region is simulated by kinetic software to obtain the predicted solution temperature T predict ; And the solution treatment system of nickel-based single crystal high temperature alloy is formulated as follows: put the nickel-based single crystal high temperature alloy at T1 temperature, then slowly heat it to T2 temperature, and keep it warm; after the insulation treatment, slowly heat it to T3 temperature; then cool it to room temperature; where T1 = Tγ′ -T0, T2 = T predict , T3=T in -T0; wherein T0 = 3-7°C. Here, in the above method of the present application, by continuously heating at a relatively low temperature - keeping warm at a medium temperature stage - continuously and slowly heating at a high temperature, the process is simple, and the degree of homogenization of the alloy can be improved and the formation of initial melting holes can be avoided simultaneously, thereby ensuring the performance of the alloy.
[0027] Among them, the slow heating treatment in the T1-T2 stage is helpful to pre-homogenize the alloy, increase the melting temperature of the interdendritic eutectic structure and reduce the internal thermal stress of the sample; the long-term heat preservation treatment in the T2 stage further improves the homogenization degree of the alloy and increases the melting temperature of the interdendritic eutectic structure; the slow heating treatment in the T2-T3 stage further improves the homogenization of the alloy, and the maximum solution treatment temperature T3 is lower than T in , which can avoid the initial melting of the alloy caused by long-term high-temperature insulation, thereby avoiding the formation of a large number of initial melting holes.
[0028] 2. Further, for different alloy systems, the solution temperature (T predict ) The residual segregation ratio of Re element (δ t <1.7) and the residual segregation ratio of Ta element (δ t >0.85). Among them, the degree of homogenization of the alloy during the solution treatment process mainly depends on the mutual diffusion of alloying elements. According to Fick's first law and Fick's second law, the degree of homogenization between the dendrite trunk and the dendrites will depend on the diffusion distance, diffusion time, diffusion coefficient and element concentration gradient. Among them, the diffusion distance is the primary dendrite spacing (l), the diffusion coefficient is determined by the temperature and the type of alloying elements, and the element concentration gradient is determined by the dendrite element segregation ratio (δ0); and the Re element is the refractory element with the most serious enrichment in the dendrite trunk, and the Ta element is the refractory element with the most serious enrichment in the dendrites. Therefore, the predicted solution temperature is determined by the residual segregation ratio of the Re and Ta elements, which can ensure the homogenization of the alloy dendrite trunk structure and the interdendritic structure.
[0029] 3. The method for formulating a solution treatment system provided by the present invention significantly reduces the cycle of the solution treatment system of nickel-based single crystal high-temperature alloys, and by inputting the organizational parameters of different cast alloys (such as primary dendrite spacing l and dendrite element segregation ratio δ0), the predicted solution temperature can be obtained. Therefore, the method of the present application is universal and can be widely used in formulating a solution treatment system for nickel-based single crystal high-temperature alloys. BRIEF DESCRIPTION OF THE DRAWINGS
[0030] In order to more clearly illustrate the implementation methods of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for the implementation methods or the description of the prior art. The drawings described below are only exemplary, and for ordinary technicians in this field, other implementation drawings can be derived from the provided drawings without creative work.
[0031] Figure 1 Schematic diagram of dendrite spacing in Example 1 of the present invention;
[0032] Figure 2 The EMPA measurement of the dendrite trunk / interdendrite element segregation ratio for Example 1 of the present invention;
[0033] Figure 3 This is a schematic diagram of determining the characteristic phase transition temperature from the DSC curve of Example 1 of the present invention;
[0034] Figure 4 The segregation ratio of the elements Re and Ta obtained by DICTRA simulation in Example 1 of the present invention;
[0035] Figure 5 is a microstructure diagram of the alloy after solution treatment according to Example 1 of the present invention;
[0036] Figure 6 is a microstructure diagram of the alloy after solution treatment according to Example 2 of the present invention;
[0037] Figure 7 This is the microstructure of the alloy after solution treatment in Comparative Example 1 of the present invention;
[0038] Figure 8 This is the microstructure of the alloy after solution treatment in Comparative Example 2 of the present invention;
[0039] Fig. 9 This is the microstructure diagram of the alloy after solution treatment in Comparative Example 3 of the present invention;
[0040] Fig.10 It is a flow chart for formulating the solution treatment system of the present invention and a schematic diagram of the solution treatment system. DETAILED DESCRIPTION
[0041] In order to more clearly illustrate the implementation methods of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for the implementation methods or the description of the prior art. The drawings described below are only exemplary, and for ordinary technicians in this field, other implementation drawings can be derived from the provided drawings without creative work.
[0042] According to an embodiment of the present invention, a method for formulating a solution treatment system for a nickel-based single crystal high-temperature alloy is provided, according to the characteristic phase transition temperature (γ′ phase re-dissolution temperature T γ′ , initial melting temperature T in ) and predicted solution temperature T predict Formulate a solution treatment system; the solution treatment system is:
[0043] The nickel-based single crystal high-temperature alloy is placed at a temperature of T1, and then heated to a temperature of T2 at a rate of 0.5 to 1°C / min, and subjected to heat preservation treatment; after the heat preservation treatment, the alloy is heated to a temperature of T3 at a rate of 0.5 to 1°C / 30min; and then cooled to room temperature;
[0044] Among them, the nickel-based single crystal high temperature alloy includes elements Re and Ta;
[0045] T1=T γ′ -T0, T2 = T predict , T3=T in -T0; wherein, T0 = 3 ~ 7 ° C.
[0046] T γ′ is the γ′ phase re-dissolution temperature, which means that when the cast alloy is heated to T γ′ After that, the γ′ phase will dissolve back and transform into the γ phase. This phase transformation process will generate internal stress. γ′ Starting the solution treatment at a high temperature will cause the γ′ phase to dissolve back quickly, resulting in a large amount of internal stress inside the alloy, which is not conducive to improving the structural integrity of the alloy. In order to avoid this problem, the initial temperature of the solution treatment system is reduced from T1 to T γ′ Below, it helps to improve the structural integrity of the alloy structure. At the same time, from the lower temperature T γ′ Slow heating helps promote the diffusion of elements in the eutectic structure between dendrites, thereby increasing the melting temperature of the eutectic structure and reducing the tendency of the initial melting holes to form. predict It indicates the minimum solution temperature required for the residual segregation coefficient of Re and Ta to reach the critical value. At this temperature, solution treatment can avoid the increase in the number of initial melting holes caused by long-term heat preservation treatment at too high a temperature, while taking into account the economic feasibility of the system. Therefore, the intermediate temperature T2 corresponding to the continuous heat preservation treatment in this application is determined as T predict . And T in It is the initial melting temperature of the cast alloy, indicating the melting temperature of the eutectic structure between the dendrites of the cast structure. When the temperature reaches this temperature, a large number of initial melting holes will be formed. Therefore, the T3 temperature represents the highest temperature of the solution treatment system, which needs to be lower than the initial melting temperature T of the alloy. in , to avoid the initial melting of the alloy and the formation of initial melting holes.
[0047] Among them, the melting temperature of the eutectic structure is closely related to its alloy composition. The alloy is subjected to solid solution treatment at high temperature, which will promote element diffusion and thus change the element content of the eutectic structure, causing its melting point to change accordingly. Specifically, after high-temperature heat preservation treatment, the content of Ta and Al elements in the eutectic structure decreases, and the melting temperature gradually increases.
[0048] In some embodiments, the insulation treatment time is 4 to 6 hours.
[0049] In some embodiments, the characteristic phase transition temperature (γ′ phase re-dissolution temperature T γ′ and initial melting temperature T in ). The principle of using differential scanning calorimeter (DSC) to measure the characteristic phase transition temperature of an alloy is that the phase transition of an alloy during the heating process is an endothermic process. The differential scanning calorimeter can accurately measure the change in heat flow, and thus accurately reflect the temperature and heat change at which the alloy undergoes phase transition. Cast nickel-based single crystal high-temperature alloys will undergo three major phase transitions during the heating process: the γ′ phase dissolves back into the γ phase, the interdendritic eutectic structure melts and transforms into the liquid phase, and the γ phase melts and transforms into the liquid phase. The three correspond to the γ′ phase dissolution temperature T γ′ , initial melting temperature T in and solidus temperature.
[0050] In some embodiments, the predicted solution temperature T predict The determination includes the following steps:
[0051] Determine characteristic microstructure parameters: Determine characteristic microstructure parameters of cast nickel-based single crystal high-temperature alloy, including primary dendrite spacing l and dendrite element segregation ratio δ0;
[0052] Determine the predicted solution temperature T predict :The primary dendrite spacing l and dendrite element segregation ratio δ0 are input into the DICTRA kinetic software to simulate the diffusion behavior of alloy elements in the dendrite trunk / interdendrite region at different solution temperatures; when the residual segregation ratio of the element meets the set conditions, the corresponding minimum solution temperature is determined as the predicted solution temperature T predict .
[0053] The solidification process of metal materials in actual production belongs to non-equilibrium solidification. The solid-liquid interface advances in the form of dendrites, which will cause solidification segregation of alloy elements and form dendrite trunk structure and inter-dendritic structure. Among them, the dendrite trunk structure is enriched with high-melting point refractory elements, and the inter-dendritic structure is enriched with low-melting point elements. In order to obtain excellent high-temperature creep resistance, a large amount of refractory elements such as Mo, Ta, W and Re are added to nickel-based single crystal high-temperature alloys, which leads to serious solidification segregation in the cast nickel-based single crystal alloy and aggravates the structural heterogeneity between the dendrite trunk and the dendrites. The solidification segregation coefficient (i.e., the dendrite element segregation ratio δ0) is an important parameter for evaluating the degree of dendrite segregation of alloy elements. Its value is the ratio of the dendrite trunk element content to the inter-dendritic element content. When the alloy undergoes homogenization solution treatment, the dendrite residual segregation coefficient (i.e., the element residual segregation ratio δ0) is used. t ) indicates the degree of homogenization of the alloy solidification structure.
[0054] For metal alloy materials, the higher the solution treatment temperature, the further it can promote element diffusion, thereby reducing the residual segregation ratio of alloy elements. However, if the solution temperature is too high, it will also cause a large number of initial melting holes in the alloy and increase the preparation cost. Therefore, the present invention proposes a more reasonable solution treatment system, which can avoid long-term solution treatment at high temperature while ensuring a reasonable residual segregation ratio, effectively reducing the number of initial melting holes and preparation costs of the alloy. The predicted solution temperature means the lowest solution treatment temperature at which the residual segregation ratio reaches the critical value. Therefore, the predicted solution temperature is the lowest solution temperature obtained by simulation that can meet the requirements.
[0055] In some embodiments, when determining the predicted solution temperature T predict In the step, the setting conditions are: the residual segregation ratio of the element Re is less than 1.7, and the residual segregation ratio of the element Ta is greater than 0.85. The optimal solution treatment temperature T predict The criterion for determining the residual segregation ratio of Re and Ta elements is based on the fact that Re is the refractory element with the most serious enrichment in the dendrite trunk, Ta is the refractory element with the most serious enrichment between dendrites, and Re is the refractory element with the smallest diffusion coefficient in nickel-based single crystal high-temperature alloys. t ) can effectively reflect the degree of homogenization of the alloy dendrite trunk structure and interdendritic structure.
[0056] In some embodiments, the nickel-based single crystal high temperature alloy is a third generation nickel-based single crystal high temperature alloy. The above method is also applicable to the nickel-based single crystal high temperature alloy containing Re and Ta elements, and thus can also be applied to the second and fourth generation nickel-based single crystal high temperature alloys. This is because Re and Ta elements are the two elements with the largest solidification segregation coefficients in nickel-based single crystal high temperature alloys, and Re element is also the alloy element with the smallest diffusion coefficient.
[0057] On the other hand, the present invention also provides a solution treatment method for a nickel-based single crystal high temperature alloy, wherein the nickel-based single crystal high temperature alloy is subjected to a solution treatment to obtain a nickel-based single crystal high temperature alloy after the solution treatment, wherein the solution treatment adopts the following solution treatment system:
[0058] The nickel-based single crystal high-temperature alloy is placed at a temperature of T1, then heated to a temperature of T2 at a rate of 0.5 to 1°C / min, and subjected to heat preservation treatment; after the heat preservation treatment, the temperature is raised to a temperature of T3 at a rate of 0.5 to 1°C / 30min; and then cooled to room temperature;
[0059] Wherein, the nickel-based single crystal high temperature alloy includes elements Re and Ta;
[0060] T1=T γ′ -T0, T2 = T predict , T3=T in -T0; where T0 = 3-7°C; T γ′ is the γ′ phase remelting temperature, T in is the initial melting temperature and T predict To predict the solution temperature.
[0061] In another aspect, the present invention further provides a nickel-based single crystal high-temperature alloy after solid solution treatment, wherein in the nickel-based single crystal high-temperature alloy after solid solution treatment: the initial melting hole area fraction is <0.01%; and / or
[0062] The eutectic content is 0; and / or
[0063] The residual segregation ratio of the element Re is less than 1.4; the residual segregation ratio of the element Ta is greater than 0.9.
[0064] Furthermore, the nickel-based single crystal high-temperature alloy after solution treatment is obtained by the above-mentioned solution treatment method.
[0065] The present invention is further described below with reference to specific embodiments and comparative examples.
[0066] Example 1
[0067] This embodiment provides a method for formulating a solution treatment system for a nickel-based single crystal high-temperature alloy. Fig.10 As shown, the nickel-based single crystal high-temperature alloy is a third-generation nickel-based single crystal high-temperature alloy, and its components are, by mass fraction, Al5.2wt.%, Cr5.8wt.%, Co7.3wt.%, Ta5.8wt.%, Mo1.7wt.%, W7.7wt.%, Re4.5wt.%, and the balance is Ni; the master alloy ingot is melted according to the components, and the nickel-based single crystal high-temperature alloy test rod is prepared by a conventional directional solidification method, and the single crystal preparation method includes a high speed solidification method (HRS) and a liquid metal cooling method (LMC);
[0068] The specific steps of the solution treatment system are as follows:
[0069] Determine the characteristic organizational parameters (i.e. determine the characteristic parameters of the as-cast organizational structure): Cut a metallographic specimen (φ16mm*7mm) from the as-cast test bar of the nickel-based single crystal high-temperature alloy, and use the metallographic method to calculate the average primary dendrite spacing, such as Figure 1 As shown, the dendrite element segregation ratio δ0 (element dendrite trunk / inter-dendrite segregation ratio) was determined by electron probe microanalysis (EPMA), as shown in Figure 2 As shown in the figure, a sample (φ3mm*1.6mm) was cut from a nickel-based single crystal high-temperature alloy cast test rod, and the surface oxidation traces were removed. The characteristic phase transition temperature points of the cast alloy were measured using a differential scanning calorimeter (DSC), including the γ′ phase resolubility temperature T γ′ , initial melting temperature T in ,like Figure 3 As shown; the characteristic organizational parameters of the as-cast structure of Example 1 are measured and shown in Table 1, where L=2l; wherein the as-cast nickel-based single crystal high-temperature alloy will undergo three major phase changes during the heating process, the γ′ phase dissolves back into the γ phase, the interdendritic eutectic structure melts and transforms into the liquid phase, and the γ phase melts and transforms into the liquid phase, and the three correspond to the γ′ phase dissolution temperature T γ′ , initial melting temperature T in The solidus temperature, in this embodiment, corresponds to the temperature Figure 3 shown.
[0070] Determine the predicted solution temperature T predict The characteristic microstructure parameters (l, δ0) of Example 1 in Table 1 were input into the DICTRA kinetic simulation software to simulate the residual segregation ratio of the alloy elements after being kept at different solution temperatures for 5 h. The predicted solution temperature T was defined as follows: the residual segregation ratio of the Re element was less than 1.7 and the residual segregation ratio of the Ta element was greater than 0.85. predict (T2 = 1330°C); Figure 4 The segregation ratios of Re and Ta elements in Example 1 before and after solution treatment at 1330°C for 5 h are shown;
[0071] Formulate a solution treatment system: According to the γ′ phase re-dissolution temperature T γ′ , initial melting temperature T in and predicted solution temperature T predict A solution treatment system is formulated. For the nickel-based single crystal high-temperature alloy of this embodiment, the solution treatment system is formulated as follows:
[0072] The nickel-based single crystal high-temperature alloy is directly placed in a heat treatment furnace at a temperature of 1280°C, and then in The temperature was raised to 1330℃ at a heating rate of 1℃ / 30m inThe temperature was slowly raised to the highest solution temperature of 1341°C at a heating rate of 100 °C. After the solution was completed, the furnace was opened, the sample was taken out and air-cooled to room temperature.
[0073] The structure of the nickel-based single crystal high-temperature alloy after solution treatment in this embodiment is as follows: Figure 5 It can be seen that after the solution treatment system of this embodiment, the eutectic structure in the nickel-based single crystal high-temperature alloy has been completely eliminated, and basically no initial melting holes are formed. The percentage of the initial melting hole area is shown in Table 2.
[0074] The single crystal test rod after the solution treatment of this embodiment was subjected to subsequent secondary aging treatment, that is, the single crystal test rod after the solution treatment was directly placed in a heat treatment furnace at 1100°C for 6 hours and air-cooled; then the single crystal test rod was directly placed in a heat treatment furnace at 870°C for 24 hours and air-cooled. Thus, the single crystal test rod in the standard heat treatment state of this embodiment was obtained; the residual dendrite segregation after the standard heat treatment was measured using an electron probe microscope (EPMA), and the residual segregation ratio of Re was 1.32, and the residual segregation ratio of Ta was 0.93, as shown in Table 2.
[0075] The single crystal test rod in the standard heat-treated state was processed into a standard endurance test specimen, and an endurance test was carried out at 1120℃ / 137MPa, and the endurance life reached 131h.
[0076] Example 2
[0077] The present embodiment provides a method for formulating a solution treatment system for a nickel-based single crystal high-temperature alloy, wherein the nickel-based single crystal high-temperature alloy is a third-generation nickel-based single crystal high-temperature alloy, and its components, by mass fraction, are: Al5.8wt.%, Cr4.3wt.%, Co7.3wt.%, Ta6.2wt.%, Mo2.3wt.%, W6.4wt.%, Re3.9wt.%, and the balance is Ni; a master alloy ingot is melted according to the components, and a nickel-based single crystal high-temperature alloy test rod is prepared by a conventional directional solidification method, and the single crystal preparation method includes a high speed solidification method (HRS) and a liquid metal cooling method (LMC);
[0078] The specific steps of the solution treatment system are as follows:
[0079] Determination of characteristic organizational parameters: metallographic specimens (φ16mm*7mm) were cut from the cast test bars of nickel-based single crystal high-temperature alloys, and the average primary dendrite spacing was statistically calculated using the metallographic method, and the dendrite element segregation ratio δ0 (element dendrite trunk / inter-dendrite segregation ratio) was determined using electron probe microanalysis (EPMA); specimens (φ3mm*1.6mm) were cut from the cast test bars of nickel-based single crystal high-temperature alloys, and the surface oxidation traces were removed. The characteristic phase transition temperature points of the cast alloys, including the γ′ phase resolubility temperature T were measured using a differential scanning calorimeter (DSC). γ′ , initial melting temperature T in; The characteristic structural parameters of the as-cast structure of Example 1 are measured and shown in Table 1, where L = 2l;
[0080] Determine the predicted solution temperature T predict The characteristic organizational parameters (l, δ0) of Example 2 in Table 1 were input into the DICTRA kinetic simulation software to simulate the residual segregation ratio of the alloy elements after being kept at different solution temperatures for 5 h. The predicted solution temperature T was defined as follows: the residual segregation ratio of the Re element was less than 1.7 and the residual segregation ratio of the Ta element was greater than 0.85. predict (T2 = 1335°C);
[0081] Formulate a solid solution treatment system: According to the characteristic phase transition temperature of the cast alloy (γ′ phase re-dissolution temperature T γ′ , initial melting temperature T in ) and predicted solution temperature T predict A solution treatment system is formulated. For the nickel-based single crystal high-temperature alloy of this embodiment, the solution treatment system is formulated as follows:
[0082] The nickel-based single crystal high-temperature alloy is directly placed in a heat treatment furnace at a temperature of 1274°C, and then heated to 1335°C at a heating rate of 0.8°C / min and kept warm for 5 hours; after the insulation treatment, the temperature is slowly increased to the maximum solid solution temperature of 1344°C at a heating rate of 0.8°C / 30min; after the solid solution is completed, the furnace is opened, the sample is taken out and air-cooled to room temperature.
[0083] The structure of the nickel-based single crystal high-temperature alloy after solution treatment in this embodiment is as follows: Figure 6 It can be seen that after the solution treatment system of this embodiment, the nickel-based single crystal high-temperature alloy basically has no initial melting holes, the eutectic structure in the alloy has been completely eliminated, and basically no initial melting holes are formed. The percentage of the initial melting hole area is shown in Table 2.
[0084] The single crystal test rod after the solution treatment of this embodiment was subjected to subsequent secondary aging treatment, that is, the single crystal test rod after the solution treatment was directly placed in a heat treatment furnace at 1100°C for 6 hours and air-cooled; then the single crystal test rod was directly placed in a heat treatment furnace at 870°C for 24 hours and air-cooled, so as to obtain the single crystal test rod in the standard heat treatment state of this embodiment. The residual dendrite segregation of the alloy after standard heat treatment was measured using an electron probe microscope (EPMA), and the residual segregation ratio of Re was 1.38, and the residual segregation ratio of Ta was 0.91, as shown in Table 2.
[0085] The single crystal test rod in the standard heat-treated state was processed into a standard endurance test specimen, and an endurance test was carried out at 1120℃ / 137MPa, and the endurance life reached 145h.
[0086] Comparative Example 1
[0087] The present comparative example provides a method for formulating a solution treatment system of a nickel-based single crystal high-temperature alloy, wherein the nickel-based single crystal high-temperature alloy is a third-generation nickel-based single crystal high-temperature alloy, and its components are, by mass fraction, Al5.2wt.%, Cr5.8wt.%, Co7.3wt.%, Ta5.8wt.%, Mo1.7wt.%, W7.7wt.%, Re4.5wt.%, and the balance is Ni; a master alloy ingot is melted according to the components, and a nickel-based single crystal high-temperature alloy test rod is prepared by a conventional directional solidification method, and the single crystal preparation method includes a high speed solidification method (HRS) and a liquid metal cooling method (LMC);
[0088] The specific steps of the solution treatment system are as follows:
[0089] Determination of characteristic microstructure parameters: Cut a sample (φ3mm*1.6mm) from a nickel-based single crystal high-temperature alloy cast test rod, remove the surface oxidation traces, and use a differential scanning calorimeter (DSC) to measure the characteristic phase transition temperature points of the cast alloy, including the initial melting temperature T in ; The characteristic organizational parameters of the as-cast structure of Example 1 are measured and shown in Table 1;
[0090] Determine the predicted solution temperature T predict The characteristic microstructure parameters (l, δ0) of Comparative Example 1 in Table 1 were input into the DICTRA kinetic simulation software to simulate the residual segregation ratio of the alloy elements after being kept at different solution temperatures for 5 h. The predicted solution temperature T was defined as follows: the residual segregation ratio of the Re element was less than 1.7 and the residual segregation ratio of the Ta element was greater than 0.85. predict (T2 = 1330°C);
[0091] Then according to the initial melting temperature T in According to the traditional step-by-step solution treatment, the highest initial melting temperature is set as the initial melting temperature (T in =1345℃) is 5℃ lower, that is, the highest solid solution temperature is 1340℃, and it is gradually reduced by 10℃, namely 1330℃ / 5h, 1320℃ / 3h, 1310℃ / 2h, 1300℃ / 1h, that is, the nickel-based single crystal high-temperature alloy is directly placed in a heat treatment furnace with a temperature of 1300℃, and the temperature is increased to 1310℃ after keeping it for 1h, and then to 1320℃ after keeping it for 2h, and then to 1330℃ after keeping it for 3h, and then to 1340℃ after keeping it for 5h, and the heating rate is 10℃ / min; after the solid solution is completed, the furnace is opened, the sample is taken out and air-cooled to room temperature.
[0092] The structure of the nickel-based single crystal high-temperature alloy after solution treatment in this comparative example is as follows: Figure 7It can be seen that the conventional step-by-step solution treatment system has a long total solution time and a long high-temperature holding time. Although the eutectic structure has been completely eliminated, a large number of solution pores are still generated even if the alloy is solution treated below the initial melting temperature. The percentage of the initial melting pore area is shown in Table 2.
[0093] The single crystal test rod after the solution treatment of this comparative example was subjected to subsequent secondary aging treatment, that is, the single crystal test rod after the solution treatment was directly placed in a heat treatment furnace at 1100°C for 6 hours and air-cooled; then the single crystal test rod was directly placed in a heat treatment furnace at 870°C for 24 hours and air-cooled, thereby obtaining the single crystal test rod in the standard heat-treated state of this comparative example. The residual dendrite segregation of the alloy after standard heat treatment was measured using an electron probe microscope (EPMA), and the residual segregation ratio of Re was 1.35, and the residual segregation ratio of Ta was 0.90, as shown in Table 2. Although the residual segregation ratios of Re and Ta in Comparative Example 1 can meet the parameters required by this application, the total solution treatment time used in Comparative Example 1 is as high as 16 hours, which is much higher than 11 hours in Example 1, which results in a large number of initial melting holes in Comparative Example 1 (see Table 2) and greatly increases the preparation cost of the alloy.
[0094] The standard heat-treated single crystal test bar was processed into a standard endurance test specimen, and an endurance test was conducted at 1120°C / 137MPa, and the endurance life reached 95h. Since the solid solution treated structure of Comparative Example 1 contains a large number of initial melting holes, which reduce the effective bearing area of the alloy and become the source of defects during the deformation process of the sample, the high-temperature endurance life of Comparative Example 1 is lower than that of Example 1.
[0095] Comparative Example 2
[0096] The present comparative example provides a method for formulating a solution treatment system of a nickel-based single crystal high-temperature alloy, wherein the nickel-based single crystal high-temperature alloy is a third-generation nickel-based single crystal high-temperature alloy, and its components are, by mass fraction, Al5.2wt.%, Cr5.8wt.%, Co7.3wt.%, Ta5.8wt.%, Mo1.7wt.%, W7.7wt.%, Re4.5wt.%, and the balance is Ni; a master alloy ingot is melted according to the components, and a nickel-based single crystal high-temperature alloy test rod is prepared by a conventional directional solidification method, and the single crystal preparation method includes a high speed solidification method (HRS) and a liquid metal cooling method (LMC);
[0097] The specific steps of the solution treatment system are as follows:
[0098] Determination of characteristic organizational parameters: metallographic specimens (φ16mm*7mm) were cut from the cast test bars of nickel-based single crystal high-temperature alloys, and the average primary dendrite spacing was statistically calculated using the metallographic method, and the dendrite element segregation ratio δ0 (element dendrite trunk / inter-dendrite segregation ratio) was determined using electron probe microanalysis (EPMA); specimens (φ3mm*1.6mm) were cut from the cast test bars of nickel-based single crystal high-temperature alloys to remove surface oxidation marks, and the initial melting temperature T of the alloy was measured using a differential scanning calorimeter (DSC). in , the results are shown in Table 1;
[0099] Determine the predicted solution temperature T predict The characteristic microstructure parameters (l, δ0) of Comparative Example 2 in Table 1 were input into the DICTRA kinetic simulation software to simulate the residual segregation ratio of the alloy elements after being kept at different solution temperatures for 5 h. The predicted solution temperature T was defined as follows: the residual segregation ratio of the Re element was less than 1.7 and the residual segregation ratio of the Ta element was greater than 0.85. predict (T2 = 1330°C);
[0100] Formulate a solid solution treatment system: According to the characteristic phase transition temperature of the cast alloy (γ′ phase re-dissolution temperature T γ′ and initial melting temperature T in ) and predicted solution temperature T predict The solution treatment system is formulated as follows: the nickel-based single crystal high-temperature alloy is directly placed in a heat treatment furnace at a temperature of 1330°C, kept at this temperature for 5 hours, and then heated to 1341°C at a heating rate of 1°C / 30min; after the solution treatment is completed, the furnace is opened, the sample is taken out and air-cooled to room temperature.
[0101] The structure of the nickel-based single crystal high-temperature alloy after solution treatment in this comparative example is as follows: Figure 8 It can be seen that the comparative example did not perform the slow heating treatment in the T1-T2 stage but directly heated to the T2 temperature for a long time. At this time, the eutectic structure has been completely eliminated, but because the alloy has not undergone pre-homogenization treatment, the melting temperature of the eutectic structure between the dendrites is low, resulting in the formation of a large number of solid solution pores in the alloy during the subsequent insulation and heating process, but the number of solid solution pores is less than that of comparative example 1. The percentage of the initial melting pore area is shown in Table 2.
[0102] The single crystal test rod after the solution treatment of this comparative example was subjected to subsequent secondary aging treatment, that is, the single crystal test rod after the solution treatment was directly placed in a heat treatment furnace at 1100°C for 6 hours, and air-cooled; then the single crystal test rod was directly placed in a heat treatment furnace at 870°C for 24 hours, and air-cooled. Thus, the standard heat-treated single crystal test rod of this embodiment was obtained. The residual dendrite segregation of the alloy after standard heat treatment was measured using an electron probe microscope (EPMA). The residual segregation ratio of Re was 1.43, and the residual segregation ratio of Ta was 0.88, as shown in Table 2.
[0103] The standard heat-treated single crystal test bar was processed into a standard endurance test specimen, and an endurance test was conducted at 1120°C / 137MPa, and the endurance life reached 118h. Since the solution-treated structure of Comparative Example 2 contains a large number of initial melting holes, which reduce the effective bearing area of the alloy and become the source of defects during the deformation of the sample, the high-temperature endurance life of Comparative Example 2 is lower than that of Example 1.
[0104] Comparative Example 3
[0105] The present comparative example provides a method for formulating a solution treatment system for a nickel-based single crystal high-temperature alloy, wherein the nickel-based single crystal high-temperature alloy is a third-generation nickel-based single crystal high-temperature alloy, and its components are as follows by mass fraction: Al5.2wt.%, Cr5.8wt.%, Co7.3wt.%, Ta5.8wt.%, Mo1.7wt.%, W7.7wt.%, Re4.5wt.%, and the balance is Ni; a master alloy ingot is melted according to the components, and a nickel-based single crystal high-temperature alloy test rod is prepared by a conventional directional solidification method, and the single crystal preparation method includes a high speed solidification method (HRS) and a liquid metal cooling method (LMC);
[0106] The specific steps of the solution treatment system are as follows:
[0107] Determination of characteristic organizational parameters: metallographic specimens (φ16mm*7mm) were cut from the cast test bars of nickel-based single crystal high-temperature alloys, and the average primary dendrite spacing was statistically calculated using the metallographic method, and the dendrite element segregation ratio δ0 (element dendrite trunk / inter-dendrite segregation ratio) was determined using electron probe microanalysis (EPMA); specimens (φ3mm*1.6mm) were cut from the cast test bars of nickel-based single crystal high-temperature alloys to remove surface oxidation traces, and the characteristic phase transition temperature points of the cast alloys, including the γ′ phase resolubility temperature T were measured using a differential scanning calorimeter (DSC). γ′ , initial melting temperature T in ;The results are shown in Table 1;
[0108] Determine the predicted solution temperature T predict The characteristic organizational parameters (l, δ0) of Comparative Example 3 in Table 1 were input into the DICTRA kinetic simulation software to simulate the residual segregation ratio of the alloy elements after being kept at different solution temperatures for 5 h. The predicted solution temperature T was defined as follows: the residual segregation ratio of the Re element was less than 1.7 and the residual segregation ratio of the Ta element was greater than 0.85. predict (T2 = 1330°C);
[0109] Formulate a solid solution treatment system: According to the characteristic phase transition temperature of the cast alloy (γ′ phase re-dissolution temperature T γ′ and initial melting temperature T in ) and predicted solution temperature T predictThe solution treatment system is formulated as follows: the nickel-based single crystal high-temperature alloy is directly placed in a heat treatment furnace at a temperature of 1280°C, and then the temperature is increased to 1333°C at a rate of 1°C / 30min, and after being kept at this temperature for 5h, the temperature is increased to 1341°C at a heating rate of 10°C / min and kept at this temperature for 4h; after the solution treatment is completed, the furnace is opened, the sample is taken out, and air-cooled to room temperature.
[0110] The nickel-based single crystal high temperature alloy of this comparative example was not subjected to the slow heating treatment from T2 to T3, but was heated to T3 temperature at a relatively high heating rate and subjected to the heat preservation solid solution treatment. The obtained microstructure is as follows: Fig. 9 It can be seen that due to the high heating rate, the diffusion of elements between the alloy dendrites and the dendrite stem is insufficient, resulting in the formation of a large number of solid solution pores in the alloy during the high temperature and long-time heat preservation solid solution treatment. The percentage of the initial melting pore area is shown in Table 2.
[0111] The single crystal test rod after the solution treatment of this comparative example was subjected to subsequent secondary aging treatment, that is, the single crystal test rod after the solution treatment was directly placed in a heat treatment furnace at 1100°C for 6 hours, and air-cooled; then the single crystal test rod was directly placed in a heat treatment furnace at 870°C for 24 hours, and air-cooled. Thus, the standard heat-treated single crystal test rod of this comparative example was obtained. The residual dendrite segregation of the alloy after standard heat treatment was measured using an electron probe microscope (EPMA). The residual segregation ratio of Re was 1.41, and the residual segregation ratio of Ta was 0.92, as shown in Table 2.
[0112] The standard heat-treated single crystal test bar was processed into a standard endurance test specimen, and an endurance test was conducted at 1120°C / 137MPa, and the endurance life reached 118h. Since the solution-treated structure of Comparative Example 3 contains a large number of initial melting holes, which reduce the effective bearing area of the alloy and become the source of defects during the deformation of the sample, the high-temperature endurance life of Comparative Example 3 is lower than that of Example 1.
[0113] Table 1 Characteristic microstructure parameters of cast nickel-based single crystal high-temperature alloys in the embodiments and comparative examples
[0114]
[0115] (- indicates that the comparative example does not require this parameter) Table 2 Initial melting hole area fraction after solution treatment of the alloys of Examples 1, 2 and Comparative Examples 1, 2, and 3
[0116]
[0117] It is easy for those skilled in the art to understand that, without conflict, the advantageous technical features of the above-mentioned methods can be freely combined and superimposed.
[0118] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principle of the present invention shall be included in the protection scope of the present invention. The above description is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and variations can be made without departing from the technical principles of the present invention. These improvements and variations should also be regarded as the protection scope of the present invention.
Claims
1. A method for formulating a solution treatment system for a nickel-based single crystal high-temperature alloy, characterized in that: According to the characteristic phase transition temperature and predicted solution temperature T of the cast nickel-based single crystal high-temperature alloy predict Formulate a solution treatment system; the solution treatment system is: The nickel-based single crystal high-temperature alloy is placed at a temperature of T1, then heated to a temperature of T2 at a rate of 0.5 to 1°C / min, and subjected to a heat preservation treatment; After the heat preservation treatment is completed, the temperature is raised to T3 at 0.5-1°C / 30min; then cooled to room temperature; Wherein, the nickel-based single crystal high temperature alloy includes the elements Re and Ta; the characteristic phase transition temperature includes the γ′ phase re-dissolution temperature T γ′ and initial melting temperature T in ; T1=T γ′ -T0, T2 = T predict , T3=T in -T0; wherein, T0 = 3 ~ 7 ° C.
2. The method for formulating a solution treatment system for a nickel-based single crystal high-temperature alloy according to claim 1, characterized in that: The insulation treatment time is 4 to 6 hours.
3. The method for formulating a solution treatment system for a nickel-based single crystal high-temperature alloy according to claim 1, characterized in that: The characteristic phase transition temperature was measured by differential scanning calorimetry.
4. The method for formulating a solution treatment system for a nickel-based single crystal high-temperature alloy according to claim 1, characterized in that: The predicted solution temperature T predict The determination includes the following steps: Determine characteristic organizational parameters: Determine characteristic organizational parameters of the cast nickel-based single crystal high-temperature alloy, wherein the characteristic organizational parameters include a primary dendrite spacing l and a dendrite element segregation ratio δ0; Determine the predicted solution temperature T predict :The primary dendrite spacing l and dendrite element segregation ratio δ0 are input into the DICTRA kinetic software to simulate the diffusion behavior of alloy elements in the dendrite trunk / interdendrite region at different solution temperatures; when the residual segregation ratio of the element meets the set conditions, the corresponding solution temperature is determined as the predicted solution temperature T predict .
5. The method for formulating a solution treatment system for a nickel-based single crystal high-temperature alloy according to claim 4, characterized in that: In the determination of the predicted solution temperature T predict In the step, the setting conditions are: the residual segregation ratio of the element Re is less than 1.7, and the residual segregation ratio of the element Ta is greater than 0.
85.
6. The method for formulating a solution treatment system for a nickel-based single crystal high-temperature alloy according to claim 1, characterized in that: The nickel-based single crystal high-temperature alloy is a third-generation nickel-based single crystal high-temperature alloy.
7. A solution treatment method for a nickel-based single crystal high-temperature alloy, characterized in that: The nickel-based single crystal high temperature alloy is subjected to a solid solution treatment to obtain a nickel-based single crystal high temperature alloy after the solid solution treatment. The solid solution treatment adopts the following solid solution treatment system: The nickel-based single crystal high-temperature alloy is placed at a temperature of T1, then heated to a temperature of T2 at a rate of 0.5 to 1°C / min, and subjected to a heat preservation treatment; After the heat preservation treatment is completed, the temperature is raised to T3 at 0.5-1°C / 30min; then cooled to room temperature; Wherein, the nickel-based single crystal high temperature alloy includes elements Re and Ta; T1=T γ′ -T0, T2 = T predict , T3=T in -T0;T γ′ is the γ′ phase remelting temperature, T in is the initial melting temperature and T predict To predict the solution temperature; T0 = 3 ~ 7 ° C.
8. A nickel-based single crystal high-temperature alloy after solution treatment, characterized in that: In nickel-based single crystal high-temperature alloys after solution treatment: the initial melting void area fraction is <0.01%; and / or The eutectic content is 0; and / or The residual segregation ratio of the element Re is less than 1.4; the residual segregation ratio of the element Ta is greater than 0.
9.
9. The nickel-based single crystal high-temperature alloy after solution treatment according to claim 8, characterized in that: The nickel-based single crystal high-temperature alloy after solution treatment is obtained by the solution treatment method of claim 7.