Heat treatment method applied to laser additive manufacturing of GH4169 nickel-based superalloy

Abstract

The invention discloses a heat treatment method applied to laser additive manufacturing of a GH4169 nickel-based superalloy, and belongs to the technical field of additive manufacturing. Comprising the following steps that firstly, solid solution heat preservation is conducted on a laser additive manufacturing GH4169 alloy deposition state sample, and then air cooling is conducted to the room temperature; and 2, the sample obtained after solution treatment is subjected to two-stage aging treatment, and finally secondary air cooling is conducted to the room temperature. According to the heat treatment method applied to laser additive manufacturing of the GH4169 nickel-based superalloy, the strength and plasticity of the alloy are improved, and meanwhile material anisotropy caused in the laser additive manufacturing process is relieved.

Description

Technical Field

[0001] The invention belongs to the technical field of additive manufacturing, and specifically relates to a heat treatment method for laser additive manufacturing of GH4169 nickel-based high-temperature alloy. Background Art

[0002] GH4169 alloy is a precipitation-strengthened nickel-based high-temperature alloy. Its yield strength below 650°C ranks first among deformed high-temperature alloys. It also has good fatigue resistance, radiation resistance, oxidation resistance, corrosion resistance, as well as good processing and welding properties. It is widely used in the manufacture of high-temperature load-bearing components such as jet engine turbine blades, gas turbine blades, and turbojet combustion chambers. With the continuous development of the aerospace industry, the structural design of aircraft engines and various types of hypersonic aircraft parts has become increasingly sophisticated and complex. The use of traditional forging and casting manufacturing methods often requires subsequent precision processing, which consumes a lot of manpower and material resources. In recent years, laser additive manufacturing technology represented by selective laser melting has the advantages of high design freedom, short production cycle, and high material utilization rate. It provides a new solution for the rapid prototyping of complex and precise components in the aerospace industry. However, due to the fact that the material undergoes a cyclical thermal history during the selective laser melting process and has an ultra-fast cooling rate (10 6 -10 8 K / s), resulting in significant differences between the final deposited structure and the forged and cast parts. The traditional forging and casting heat treatment system is difficult to match the laser additive manufacturing GH4169 alloy parts, so it is necessary to improve the heat treatment scheme to match the needs of laser additive manufacturing GH4169 alloy. Summary of the invention

[0003] The purpose of the present invention is to provide a heat treatment method for laser additive manufacturing of GH4169 nickel-based high-temperature alloy, which solves the problem of improving the strength and toughness of laser additive manufacturing GH4169 alloy and improving anisotropy through heat treatment.

[0004] The technical solution adopted by the present invention is a heat treatment method for laser additive manufacturing of GH4169 nickel-based high-temperature alloy, and the specific steps are as follows:

[0005] Step 1: The deposited sample of GH4169 alloy manufactured by laser additive manufacturing is subjected to solid solution treatment and heat preservation, and then air-cooled to room temperature to obtain a sample after solid solution treatment;

[0006] Step 2: The solution treated sample is subjected to a double-stage aging treatment, followed by a second air cooling to room temperature.

[0007] In the further step 1, the temperature during the solution heat preservation process is 1080°C, and the solution heat preservation time is 1 hour.

[0008] In the further step 1, the cooling rate during the first air cooling is 40-70°C / min until it drops to room temperature.

[0009] In the further step 2, in the two-stage aging and insulation process, the primary aging temperature is 720°C, the insulation time is 8h, and the furnace is cooled to 620°C at a cooling rate of 55°C / h, and then the secondary aging is performed, the secondary aging temperature is 620°C, and the insulation time is 8h.

[0010] In the further step 2, the secondary air cooling, i.e. the second air cooling, is performed at a cooling rate of 40-70°C / min until the temperature drops to room temperature.

[0011] The beneficial effects of the present invention are:

[0012] The present invention provides a heat treatment method for laser additive manufacturing of GH4169 nickel-based high-temperature alloy. The solution treatment temperature is increased to 1080°C, which can effectively eliminate the residual stress inside the laser additive manufacturing GH4169 alloy. Most of the grains are recrystallized during the insulation process, so that the columnar grains originally parallel to the deposition direction are transformed into equiaxed grains, thereby eliminating the anisotropy of the alloy structure caused by the deposition direction.

[0013] Secondly, the grains did not grow excessively, and the high-density annealing twins improved the plasticity of the alloy. The higher solution temperature dissolved the Laves phase in the alloy, dissolving the strengthening elements back into the matrix, ensuring the maximum precipitation of γ′ and γ″ strengthening phases during the subsequent aging process, improving the strength of the alloy and making the alloy show excellent strength and plasticity. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 The inverse pole figures of the deposited GH4169 alloy before heat treatment: (a) perpendicular to the deposition direction; (b) parallel to the deposition direction;

[0015] Figure 2 The reverse pole figures of GH4169 alloy after solution treatment at 980℃ for 1h and double-stage aging treatment: (a) perpendicular to the deposition direction; (b) parallel to the deposition direction;

[0016] Figure 3 The reverse pole figures of GH4169 alloy after solution treatment at 1020℃ for 1h and double-stage aging treatment: (a) perpendicular to the deposition direction; (b) parallel to the deposition direction;

[0017] Figure 4 The reverse pole figures of GH4169 alloy after solution treatment at 1080℃ for 1h and double-stage aging treatment: (a) perpendicular to the deposition direction; (b) parallel to the deposition direction;

[0018] Figure 5The microstructure of the deposited GH4169 alloy before heat treatment;

[0019] Figure 6 The microstructure of GH4169 alloy after solution treatment at 980℃ for 1h and double-stage aging treatment;

[0020] Figure 7 The microstructure of GH4169 alloy after solution treatment at 1020℃ for 1h and double-stage aging treatment;

[0021] Figure 8 The microstructure of GH4169 alloy after solution treatment at 1080℃ for 1h and double-stage aging treatment;

[0022] Fig. 9 This is the precipitation strengthening phase morphology of GH4169 alloy after solution treatment at 1080℃ for 1h and double-stage aging treatment.

[0023] Fig.10 Schematic diagram of heat treatment method. DETAILED DESCRIPTION

[0024] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments, but the present invention is not limited to the following embodiments.

[0025] Example 1 and Comparative Examples 1-3

[0026] The present application embodiment discloses a heat treatment method for laser additive manufacturing of GH4169 nickel-based high-temperature alloy, comprising the following steps:

[0027] The GH4169 alloy was prepared by selective laser melting. The parameters of the selective laser melting were as follows: laser power of 400W, scanning speed of 900mm / s, powder layer thickness of 40μm, scanning line spacing of 100μm, and interlayer rotation of 67°. A heat treatment process for laser additive manufacturing of GH4169 alloy was formulated (Table 1), and the GH4169 high-temperature alloy formed by selective laser melting was subjected to solution treatment, primary aging, and secondary aging in sequence. The solution temperature was 980℃~1080℃ (the embodiment and the comparative example only differed in the solution temperature, see Table 1 for the specific differences), the holding time was 1h, and then air-cooled to room temperature; the primary aging temperature was 720℃, the holding time was 8h; the secondary aging temperature was 620℃, the holding time was 8h, and finally air-cooled to room temperature.

[0028] Table 1 Heat treatment process scheme corresponding to the embodiments and comparative examples

[0029]

[0030]

[0031] like Figure 1 As shown in (a) and (b), the deposited GH4169 alloy of comparative example 1 shows coarse grains and fine grains in a chessboard-like alternating distribution in the scanning direction, columnar crystals in the deposition direction, and a <001> Select the best orientation. Figure 5 This is a microscopic morphology of the deposited GH4169 alloy of comparative example 1. A large amount of chain-like Laves phase exists inside the alloy. The yield strength of the deposited GH4169 alloy of comparative example 1 is 879 MPa, the tensile strength is 1190 MPa, and the elongation is 22.8%.

[0032] like Figure 2 As shown in (a) and (b), in Comparative Example 2, after the laser additive manufacturing GH4169 alloy was subjected to solution treatment at 980°C for 1h and aging treatment, its grain morphology still maintained the characteristics of the deposited state. Figure 6 This is a microscopic morphology of the laser additively manufactured GH4169 alloy in Example 2 after solution treatment at 980℃ for 1h and aging treatment. The Laves phase is dissolved into dots, and the δ phase is precipitated inside the alloy in the form of short rods, mostly distributed along the grain boundaries. The yield strength of the GH4169 alloy in Example 2 after solution treatment at 980℃ for 1h and double-stage aging treatment is 1401MPa, the tensile strength is 1518MPa, and the elongation is 12.5%.

[0033] like Figure 3 As shown in (a) and (b), after the laser additive manufacturing GH4169 alloy in comparative example 3 was solution treated at 1020℃ for 1h and then aged, most of the grains still retained the characteristics of the deposited state, a small number of grains were recrystallized, and annealing twins appeared. Figure 7 This is the microscopic morphology of the laser additively manufactured GH4169 alloy after solution treatment at 1020℃ for 1h and aging treatment. A small amount of Laves phase and δ phase remain in the sample. The yield strength of the GH4169 alloy after solution treatment at 1020℃ for 1h and double-stage aging treatment in comparative example 3 is 1398MPa, the tensile strength is 1494MPa, and the elongation is 13.4%.

[0034] like Figure 4 As shown in (a) and (b), after the laser additive manufacturing GH4169 alloy in Example 1 was solution treated at 1080℃ for 1h and aged, most of the grains were recrystallized, and a large number of lamellar annealing twins appeared inside the grains, eliminating the structural anisotropy generated during the deposition process, and the Laves phase and δ phase were further dissolved. Fig. 9The internal strengthening phase morphology of the GH4169 alloy after solution treatment at 1080°C for 1h and double-stage aging treatment; a large amount of nano-scale γ′ phase and γ″ phase are precipitated inside the sample during the double-stage aging process. Example 1 The yield strength of the GH4169 alloy after solution treatment at 1080°C for 1h and double-stage aging treatment is 1465MPa, the tensile strength is 1538MPa, and the elongation is 18.5%, and the alloy strength and plasticity are optimal.

[0035] Table 2 Mechanical properties of samples at different solution temperatures

[0036]

[0037] In summary, the present invention provides a heat treatment method for laser additive manufacturing of GH4169 nickel-based high-temperature alloy. By optimizing the heat treatment process and the alloy microstructure, the yield strength and tensile strength of the alloy are greatly improved without losing the elongation, thereby achieving a synergistic effect of strength and toughness.

[0038] The above embodiments are merely enumerated to more clearly illustrate the technical solutions of the present invention, and are not limitations of the present invention. Any modifications to the technical solutions of the present application made by ordinary technicians in the field based on the common knowledge in the field are also within the protection scope of the present application. In short, the above embodiments are merely enumerated, and the protection scope of the present application shall be based on the scope of the attached claims.

Claims

1. A heat treatment method for laser additive manufacturing of GH4169 nickel-based high-temperature alloy, characterized in that: The specific steps are as follows: Step 1: The deposited sample of GH4169 alloy manufactured by laser additive manufacturing is subjected to solid solution treatment and heat preservation, and then air-cooled to room temperature to obtain a sample after solid solution treatment; Step 2: The solution treated sample is subjected to a double-stage aging treatment, followed by a second air cooling to room temperature.

2. The method according to claim 1, characterized in that In step 1, the temperature during the solution heat preservation process is 1080° C., and the solution heat preservation time is 1 hour.

3. The method according to claim 1, characterized in that In step 1, the cooling rate during the first air cooling is 40-70°C / min until it drops to room temperature.

4. The method according to claim 1, characterized in that In step 2, the primary aging temperature in the two-stage aging and insulation process is 720°C, the insulation time is 8h, and the furnace is cooled to 620°C at a cooling rate of 55°C / h, and then the secondary aging is performed, the secondary aging temperature is 620°C, and the insulation time is 8h.

5. The method according to claim 1, characterized in that In step 2, the secondary air cooling, i.e. the second air cooling, has a cooling rate of 40-70°C / min until it reaches room temperature.

6. GH4169 nickel-based high-temperature alloy obtained according to the method described in any one of claims 1 to 5.

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