A method for differential heat treatment of laser fusion formed inconel 625 alloy based on as-deposited non-equilibrium microstructure characteristics

Abstract

The application discloses a laser fused forming Inconel 625 alloy differential heat treatment method based on deposited state non-equilibrium organization characteristics, and relates to the technical field of metal additive manufacturing and heat treatment. The laser fused forming deposited state Inconel 625 alloy is heated to 700 DEG C at a room temperature with a temperature rising rate of 10 DEG C / min, and is kept for 13 hours; or the laser fused forming deposited state Inconel 625 alloy is heated to 1150 DEG C, kept for 1 hour, then cooled to 700 DEG C at a cooling rate of 50 DEG C / h, kept for 19 hours, then cooled to 600 DEG C at a cooling rate of 50 DEG C / h, kept for 24 hours, and then cooled to the room temperature. The application abandons the traditional 'complete homogenization' treatment concept, takes the columnar crystal, cellular substructure in the deposited state organization and Nb and Mo microsegregation enriched along the cellular boundary as available organization genetic precursors, realizes the customized synergistic regulation of mechanical properties and corrosion resistance through 'genetic utilization' or'reconstruction optimization' two paths.

Description

Technical Field

[0001] This invention relates to the fields of metal additive manufacturing and heat treatment technology, and more specifically, to a differentiated heat treatment method for Inconel 625 alloy based on the characteristics of non-equilibrium microstructure formed by laser filament forming. Background Technology

[0002] Inconel 625 alloy, with its excellent high-temperature strength, creep resistance, and corrosion resistance, is widely used in extreme service environments such as aerospace, solar thermal power generation, and high-temperature molten salt systems. Laser filament forming, as a highly efficient near-net-shape forming technology, enables the integrated manufacturing of large and complex components. However, the inherent rapid non-equilibrium solidification and multi-layer, multi-stage thermal cycling characteristics of this process easily lead to inhomogeneous microstructure, elemental segregation, and performance fluctuations. The deposited microstructure often consists of columnar crystals and cellular substructures epitaxially growing along the deposition direction, as well as subgrain-scale microsegregation of elements such as Nb and Mo. Ni and Cr are mainly enriched in the dendrite nucleus region, while Nb, Mo, and Ti are enriched due to their equilibrium distribution coefficients. k <1 During solidification, it is continuously repelled by the solid-liquid interface and eventually accumulates significantly in the interdendritic region. This chemical heterogeneity is both the source of the high strength of the deposited state and a potential cause for microstructural instability and performance degradation during subsequent service.

[0003] Traditional heat treatment approaches typically aim for "complete homogenization," intending to eliminate segregation and substructures through high-temperature solid solution treatment. However, this method eliminates inherited strengthening elements such as columnar crystals, cellular substructures, and high-density dislocations in the deposited microstructure, and easily induces recrystallization, leading to grain coarsening and a significant decrease in yield strength. On the other hand, simple stress-relief annealing at 700–900°C can easily induce the preferential precipitation of the δ phase (Ni3Nb) in the segregation zone, consuming the matrix solid solution strengthening element Nb and forming brittle channels, thus impairing plasticity, toughness, and corrosion resistance.

[0004] Therefore, how to achieve synergistic optimization of strength and corrosion resistance by making targeted adjustments based on the non-equilibrium microstructure characteristics of the deposited state while retaining the unique strength advantages of additive manufacturing is a key problem that urgently needs to be solved in this field. Summary of the Invention

[0005] The purpose of this invention is to provide a differentiated heat treatment method for Inconel 625 alloy based on the characteristics of non-equilibrium microstructure in the deposition state using laser-fused wire forming. It abandons the traditional "complete homogenization" treatment concept and uses columnar crystals, cellular substructures and Nb and Mo microsegregation along the cellular boundaries in the deposition state microstructure as usable microstructure genetic precursors. By designing differentiated heat treatment paths, it achieves synergistic regulation of mechanical properties and corrosion resistance.

[0006] To achieve the above objectives, this invention, based on the EPMA compositional analysis results of deposited and solution-treated (1150℃ / 1h) Inconel 625 alloys, uses the TTT module in JMatPro software to calculate the TTT curves of the interdendritic and equiaxed grain regions. Guided by the above calculation results, the following differentiated heat treatment paths are provided:

[0007] In view of this, the present invention provides a differentiated heat treatment method for Inconel 625 alloy based on the characteristics of the non-equilibrium microstructure in the deposition state using laser-fused wire forming.

[0008] A differentiated heat treatment method for laser-fused Inconel 625 alloy based on the non-equilibrium microstructure characteristics of the deposited state is proposed. Using laser-fused Inconel 625 alloy deposited state samples as the treatment object, the method involves heating from room temperature at a rate of 10 °C / min and performing heat treatment according to the following path: (1) Heat the laser-fused Inconel 625 alloy to 700°C and hold for 13 hours; Alternatively, the laser-fused Inconel 625 alloy can be heated to 1150°C, held for 1 hour, and then cooled to 700°C at a rate of 50°C / h and held for 19 hours. (2) Cool the alloy treated in step (1) to 600°C at 50°C / h, hold for 24 hours, and then cool to room temperature.

[0009] Furthermore, the 50℃ / h cooling is achieved through furnace cooling or programmed temperature control, and the cooling to room temperature after the 600℃ holding period is achieved through natural air cooling.

[0010] The beneficial effects of adopting the above-mentioned further technical solutions are as follows: by limiting the heating rate, the staged cooling rate and the final cooling method, the difference in precipitation behavior caused by temperature fluctuations during the heat treatment process can be reduced, so that both paths undergo a stable 600℃ two-stage aging process; this common technical feature helps to promote the continued precipitation and size homogenization of the γ″ phase, while suppressing the large-scale generation of the δ phase, thereby improving process repeatability and microstructure stability.

[0011] Furthermore, the laser-fused Inconel 625 alloy is prepared using ERNiCrMo-3 welding wire with a diameter of 1.2 mm, the substrate is 316L stainless steel plate, the laser power is 2200 W, the scanning rate is 30 mm / s, the wire feed rate is 36 mm / s, the hot wire current is 80 A, the laser focal length is 27 mm, the welding wire extension is 30 mm, the interpass temperature is 100℃, and the shielding gas is high-purity argon gas with a flow rate of 20 L / min.

[0012] Furthermore, the laser-fused Inconel 625 alloy has a deposited microstructure consisting of columnar crystals and cellular substructures epitaxially grown along the deposition direction. The primary dendrite arm spacing is 6~10 μm. Nb and Mo are enriched in the cellular boundaries and interdendritic regions, while Ni and Cr are mainly enriched in the dendrite nucleus regions. The interdendritic regions are accompanied by the precipitation of AB2-type Laves phase and MC-type carbides.

[0013] The beneficial effects of adopting the above-mentioned further technical solutions are as follows: By defining the initial sedimentary structure and its preparation parameters, the object and prerequisites for heat treatment control in this invention are clarified. The cellular substructure, high-density dislocations, and Nb and Mo segregation in the sedimentary structure provide a channel for in-situ nucleation of the γ″ phase in path (1), and also provide a comparable initial basis for eliminating segregation and improving corrosion resistance through solid solution reconstruction in path (2), thereby ensuring that the technical solution is clear, feasible, and reproducible.

[0014] Invention Mechanism: Path 1: Direct Time-Effect Enhancement Path (DA): The path includes the following stages: (1) First-level aging treatment: The laser-fused Inconel 625 alloy is heated to 700°C and held for 13 hours; (2) Secondary aging treatment: The alloy treated in step (1) is cooled to 600°C, held for 24 hours, and then cooled to room temperature.

[0015] The core design principle of this approach is to completely preserve the grain morphology and cellular substructure characteristics of the deposited state, and actively utilize the pre-existing Nb-rich regions at the cellular boundaries as preferential nucleation sites. During the first-stage aging process at 700℃, DO-rich precipitates in the supersaturated γ-matrix. 22 The ordered nanoscale γ″ phase (Ni3Nb) maintains a good semi-coherent relationship with the matrix. Due to the cellular boundaries and dislocation network significantly reducing the nucleation barrier of the γ″ phase and acting as a rapid diffusion channel for Nb, the γ″ phase preferentially desorbs and disperses in situ in Nb-rich subgrain boundary regions. Subsequent second-order aging at 600℃ further promotes the complete precipitation of the γ″ phase and optimizes its size distribution. Simultaneously, because the bulk diffusion of Nb is extremely slow at this temperature, it effectively suppresses the γ″ phase from diffusing into the thermodynamically stable δ phase (DO). a The structure undergoes a transformation, thus achieving a balance between strengthening effect and tissue stability. Simultaneously, the high-density dislocations at the cellular boundaries are effectively pinned by the γ″ phase, forming a "tissue-locking" effect that further suppresses grain boundary migration and tissue coarsening during aging. This pathway achieves a synergistic gain from precipitation strengthening, dislocation strengthening, and substructure strengthening.

[0016] The first-level aging regime of holding at 700℃ for 13 hours in Path 1 was determined based on the TTT curve obtained from JMatPro thermodynamic calculations. This temperature is near the nose temperature of γ″ phase precipitation, which can avoid δ The nucleation driving force of the γ″ phase is maximized under the premise of a large amount of precipitation; the two-stage aging process of holding at 600℃ for 24 hours can further promote precipitation and optimize the size distribution under the condition that the diffusion of Nb atoms is extremely slow at this temperature, while suppressing the γ″→δ phase transformation.

[0017] Pathway 2: Solid solution reconstruction + homogeneous precipitation path (SA): The path includes the following stages: (1) High-temperature solution treatment: The laser-fused Inconel 625 alloy was heated to 1150℃ and held for 1 hour; (2) First-level aging treatment: Cool the alloy treated in step (1) to 700°C and hold for 19 hours; (3) Secondary aging treatment: The alloy treated in step (2) is cooled to 600°C, held for 24 hours, and then cooled to room temperature.

[0018] The core design principle of this approach lies in "organism reconstruction." High-temperature solution treatment at 1150℃ allows harmful phases such as the non-equilibrium Laves phase (AB2 type) in the sedimentary state to fully dissolve back into the γ-Ni matrix, significantly reducing Nb and Mo segregation at the subgrain scale. Simultaneously, the high residual stress accumulated in the sedimentary state drives static recrystallization of columnar crystals, transforming them into an equiaxed crystal structure containing annealed twins through grain boundary bulging nucleation. The original columnar dendrites, cellular substructure, and interlayer boundaries are all eliminated. Because MC-type carbides (such as NbC) have high thermal stability, their dissolution temperature is typically above 1200℃, and they are partially retained after solution treatment. Subsequent two-stage aging promotes the precipitation of the γ″ phase, primarily through uniform nucleation, in a homogeneous supersaturated solid solution. Due to the high nucleation energy barrier and prolonged incubation period, the γ″ phase is uniformly distributed in the matrix with smaller size and higher dispersion. The growth of the precipitates is entirely acceptor-diffusion controlled, with the slow diffusion of Nb acting as the rate-controlling step, ultimately resulting in a precipitate population with a more uniform spatial distribution and a narrower size distribution. This pathway improves plasticity while maintaining good corrosion resistance.

[0019] In Pathway 2, the solution temperature of 1150℃ is higher than the re-dissolution temperature of the Laves phase but lower than the dissolution temperature of the MC-type carbides. This can eliminate harmful Laves phases and significant segregation while retaining some MC carbides. The first-stage aging at 700℃ for 19 hours extends the aging time compared to Pathway 1 to compensate for the extended incubation period caused by the high nucleation energy barrier in the homogeneous matrix, ensuring the full precipitation of the γ″ phase. The second-stage aging at 600℃ for 24 hours is the same as in Pathway 1, both used to further promote the stable precipitation of the γ″ phase and reduce the risk of δ phase formation.

[0020] The beneficial effects of this invention are as follows: Compared with existing technologies, this invention no longer regards elemental segregation and substructure in sedimentary tissues as defects, but repositions them as usable tissue genetic features, which has the following beneficial effects: (1) Enhancement mechanism synergistic gain: Through the DA path, in the case of fully inheriting the high-density dislocations in the sedimentary state (GND density approximately 2.05 × 10⁻⁶), 14 m -2 Based on the cellular substructure, the in-situ segregation region serves as the preferential nucleation channel for the γ″ strengthening phase, achieving a synergistic effect of substructure strengthening, dislocation strengthening, and precipitation strengthening. Quantitative calculations show that in the DA state alloy, fine grain strengthening contributes approximately 110.3 MPa, dislocation strengthening contributes approximately 171.8 MPa, solid solution strengthening contributes approximately 261.2 MPa, and precipitation strengthening contributes approximately 145 MPa. The tensile strength of the obtained component can reach 997.1 MPa, and the yield strength can reach 681.5 MPa, which are 15.4% and 23.8% higher than those of the deposited state, respectively.

[0021] (2) In terms of synergistic optimization of plasticity and corrosion resistance: Through the SA path, a high-temperature solid solution reconstruction mechanism is introduced to effectively reduce compositional segregation and eliminate harmful Laves phases, thereby obtaining an equiaxed crystal matrix containing annealed twins. Due to grain coarsening (average grain size increased from 39.4 μm in the deposited state to 53.2 μm) and a significant reduction in dislocation density (GND density decreased to 0.55 × 10⁻⁶), the annealing process is significantly improved. 14 m -2 The matrix softens significantly, increasing the elongation after fracture by 26.0% compared to the deposited state, reaching 54.3%. Simultaneously, due to a significant reduction in elemental segregation, the depletion of Cr and Mo in the grain boundary neighborhood is effectively alleviated, resulting in a more stable and dense passivation film. The film resistivity (Rf) and charge transfer resistance (Rct) are significantly higher than those of the deposited and DA states, and its resistance to intergranular corrosion and electrochemical corrosion is superior to both the deposited and DA states.

[0022] (3) In terms of process adaptability and customized control: This invention provides two complementary heat treatment strategies for laser additive manufacturing of nickel-based alloys: "genetic-utilization" (DA path) or "reconstruction-optimization" (SA path). The DA path is more suitable for components that aim for a balance between high strength and high strength-plasticity (such as valve blades of molten salt pumps in solar thermal power plants, which need to consider both yield strength and creep resistance), while the SA path is more suitable for components that prioritize high plasticity and high corrosion resistance (such as components that have been exposed to Cl-containing environments for a long time). - Piping and container components operating in corrosive media). A complete controllable spectrum of "strength-plasticity-corrosion resistance" is formed between the two paths, which can be customized according to the specific requirements of the components.

[0023] This invention abandons the traditional concept of "complete homogenization" and uses columnar crystals, cellular substructures and Nb and Mo microsegregation along cellular boundaries in the deposited structure as usable tissue genetic precursors. By designing differentiated heat treatment paths, it achieves synergistic regulation of mechanical properties and corrosion resistance. Attached Figure Description

[0024] Figure 1 The diagram shows two different heat treatment paths: (a) DA path: 700℃ / 13h + 600℃ / 24h; (b) SA path: 1150℃ / 1h + 700℃ / 19h + 600℃ / 24h.

[0025] Figure 2 The microstructures of Inconel 625 alloy in the deposited state and after heat treatment are compared. Figures (a) and (b) show columnar crystals and cellular substructures in the deposited state, Figures (c) and (d) show columnar crystal structures retained in the DA state, and Figures (e) and (f) show equiaxed crystals and annealed twin structures in the SA state.

[0026] Figure 3 TEM-EDS analysis of deposited alloys, (a) Laves phase; (b) MC carbides.

[0027] Figure 4 Comparison of TEM dark-field images of the γ″ strengthening phase in DA and SA state alloys ((a), (b), (c)). The γ″ phase in DA state is distributed along the cellular boundary ((d), (e), (f)). The γ″ phase in SA state is fine, uniformly and diffusely distributed.

[0028] Figure 5 The room temperature tensile stress-strain curves of the deposited, DA, and SA alloys are shown.

[0029] Figure 6 The curves show the evolution of intergranular corrosion rate as a function of immersion time for deposited, DA, and SA alloys in a slightly boiling Fe2(SO4)3-H2SO4 solution.

[0030] Figure 7 The precipitation morphology of the δ phase in Inconel 625 alloy after direct aging treatment (700℃ / 15 h): (a) SEM morphology; (b) TEM bright-field image. Detailed Implementation

[0031] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] Example 1: Direct Time-Based Enhancement Path (DA) First, Inconel 625 alloy bulk material was prepared using a laser wire forming system. 1.2 mm diameter ERNiCrMo-3 welding wire was used as the deposition material, and 316L stainless steel plate was used as the substrate. The process parameters were: laser power 2200 W, scanning rate 30 mm / s, wire feed rate 36 mm / s, hot wire current 80 A, laser focal length 27 mm, wire extension 30 mm, interlayer temperature 100℃, and high-purity argon gas protection flow rate 20 L / min. A pre-feeding method was used, with the laser spot acting on the center of the welding wire tip and maintaining approximately 50% overlap with the spot area to ensure sufficient melting of the welding wire and good molten pool spreading. The scanning strategy employed bidirectional reciprocating scanning within the layer with a 180° rotation. The resulting microstructure consisted of columnar crystals epitaxially growing along the heat flow direction and internal cellular substructures, with a primary dendrite arm spacing of approximately 6–10 μm. EPMA analysis showed that the Nb content in the interdendritic region was approximately 6.03 wt.% and the Mo content was approximately 9.52 wt.%, significantly higher than that in the dendrite nucleus region (Nb 1.87 wt.% and Mo 7.59 wt.%). Non-equilibrium precipitates, such as AB2-type Laves phase and MC-type carbides, were present in the interdendritic region.

[0033] The above-mentioned deposited samples underwent DA treatment: heating from room temperature to 700℃ at a rate of 10℃ / min, and holding at that temperature for 13 hours for primary aging; followed by furnace cooling to 600℃ at a rate of 50℃ / h, and holding at that temperature for 24 hours for secondary aging; finally, air cooling to room temperature. Microstructural characterization showed that the treated alloy retained its columnar crystal morphology and cellular substructure, with an average grain size of 41.4 μm (a very small change compared to the deposited state of 39.4 μm, within the experimental error range), and a GND density of 2.05 × 10⁻⁶. 14 m -2 (Compared to sedimentary state 2.07×10) 14 m -2 Similar). TEM analysis revealed a high-density nanoscale disk-shaped γ″ phase (DO). 22 The structure precipitates diffusely along Nb-rich subgrain boundaries, with an average diameter of approximately 12 nm and a volume fraction of approximately 14.2%; a small amount of M is also generated. 23C6 carbides, with the original Laves phase and MC carbides still retained in the interdendritic region. Room temperature tensile testing showed a tensile strength of 997.1 MPa, a yield strength of 681.5 MPa, and an elongation after fracture of 34.3%. Quantitative analysis of the strengthening mechanism indicated that fine-grained strengthening contributed 110.3 MPa, dislocation strengthening contributed 171.8 MPa, solid solution strengthening contributed 261.2 MPa, and precipitation strengthening (coherent strengthening mechanism) contributed approximately 145 MPa. The synergistic gain of precipitation strengthening, dislocation strengthening, and substructure strengthening was key to the highest yield strength achieved in the DA state. The tensile fracture surface was dominated by quasi-cleavage steps, accompanied by a small number of shallow dimples, exhibiting a mixed fracture characteristic of plasticity and quasi-cleavage.

[0034] Comparative Example 1: Using the same deposited sample as in Example 1, the temperature was increased from room temperature to 700°C at a rate of 10°C / min, and held for 15 hours for primary aging; subsequently, it was furnace cooled to 600°C at a rate of 50°C / h, and held for 24 hours for secondary aging; finally, it was air-cooled to room temperature. Under these conditions, significant δ-phase precipitation occurred in the Inconel 625 alloy. Figure 7 As shown, needle-like precipitates are densely distributed in bands along the segregation region in the SEM image; the TEM image further shows that this type of precipitate is slender and flaky, and is interspersed in the γ-Ni matrix. This morphological feature is consistent with the typical precipitation morphology of Ni3Nb type δ phase.

[0035] Comparative Example 1 shows that when the primary aging time at 700℃ is extended from 13 hours to 15 hours, the risk of the γ″ phase transforming into the δ phase in the Nb-rich segregation zone increases significantly. The δ phase consumes Nb elements in the matrix, weakening the precipitation strengthening potential of the γ″ phase; at the same time, the needle-like δ phase easily causes local stress concentration and forms crack initiation and propagation channels, thereby reducing plasticity, toughness, and corrosion resistance. Compared with Comparative Example 1, this application controls the primary aging at 700℃ / 13 hours and superimposes a secondary aging at 600℃ / 24 hours, which can promote the dispersed precipitation of the γ″ phase while inhibiting the large-scale precipitation of the δ phase, thus achieving both higher yield strength and better microstructure stability.

[0036] Example 2: Solid solution reconstruction + uniform precipitation path (SA) Deposited Inconel 625 alloy samples were prepared using the same laser filament process and materials as in Example 1.

[0037] The samples underwent SA treatment: complete solution treatment was performed by heating from room temperature to 1150℃ at a rate of 10℃ / min and holding for 1 hour; followed by first-stage aging by furnace cooling to 700℃ at a rate of 50℃ / h and holding for 19 hours; second-stage aging was then performed by furnace cooling to 600℃ at a rate of 50℃ / h and holding for 24 hours; finally, the samples were air-cooled to room temperature. Microstructural characterization revealed that the treated alloy underwent complete recrystallization, with the columnar and cellular substructures completely disappearing, forming an equiaxed grain structure containing annealed twins, and the average grain size increasing to 53.2 μm; the GND density significantly decreased to 0.55 × 10⁻⁶. 14 m -2 This indicates that the residual stress was effectively released during recrystallization. Elemental segregation between dendrites was significantly reduced. EPMA analysis showed that the Nb content in the equiaxed crystal region was 3.41 wt.% and the Mo content was 8.53 wt.%, with a more uniform distribution. The Laves phase was completely dissolved after solution treatment, with only some MC-type carbides remaining. TEM analysis showed that the γ″ phase was extremely fine and uniformly distributed in the matrix, with an average diameter of about 8 nm and a volume fraction of about 3.7%. Room temperature tensile testing showed a tensile strength of 864.9 MPa, a yield strength of 379.1 MPa (a decrease of 31.1% compared to the deposited state), and an elongation at fracture of 54.3% (an increase of 26.0% compared to the deposited state). The tensile fracture surface was covered with uniform and dense equiaxed dimples, accompanied by obvious plastic flow traces, exhibiting a typical fully plastic fracture mode. Intergranular corrosion testing (ASTM G28-02 standard, slightly boiling Fe2(SO4)3-H2SO4 solution) showed that the SA state had the lowest cumulative weight loss per unit area over 120 hours among the three states, the lowest corrosion rate, and the corrosion morphology was only shallow and narrow grain boundary trenches. Electrochemical testing (3.5 wt.% NaCl solution) further confirmed that the SA state had the most positive stable open circuit potential. 110.3 mV vs. SCE), highest low-frequency impedance amplitude, and largest film resistance (R f =3.75×10 4 Ω·cm²) and charge transfer resistance (R ct =7.38×10 5 Ω·cm 2 ), and the lowest corrosion current density (I corr =2.8×10 -6 A·cm -2 The data and passivation current density indicate that its passivation film is more stable and denser, and its corrosion resistance is significantly better than that of the deposited state and DA state.

[0038] The above descriptions are merely two specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. For example, without departing from the core idea of ​​the present invention, the heat treatment time can be appropriately adjusted according to the actual component size and performance requirements; the heat treatment path can also be combined with other surface strengthening or deformation treatment processes.

Claims

1. A differentiated heat treatment method for Inconel 625 alloy based on the characteristics of its deposited non-equilibrium microstructure, characterized in that, Using laser-fused Inconel 625 alloy deposited specimens as the treatment object, the temperature was increased from room temperature at 10℃ / min, and heat treatment was carried out according to the following path: (1) Heat the laser-fused Inconel 625 alloy to 700°C and hold for 13 hours; Alternatively, the laser-fused Inconel 625 alloy can be heated to 1150°C, held for 1 hour, and then cooled to 700°C at a rate of 50°C / h and held for 19 hours. (2) Cool the alloy treated in step (1) to 600°C at 50°C / h, hold for 24 hours, and then cool to room temperature.

2. The differentiated heat treatment method for Inconel 625 alloy based on the characteristics of its deposited non-equilibrium microstructure using laser-fused wire forming, as described in claim 1, is characterized in that... The 50℃ / h cooling is achieved through furnace cooling or programmed temperature control, and the cooling to room temperature after the 600℃ holding period is achieved through natural air cooling.

3. The differentiated heat treatment method for Inconel 625 alloy based on the characteristics of non-equilibrium microstructure in the deposition state, as described in claim 1, is characterized in that... The laser-fused Inconel 625 alloy was prepared using ERNiCrMo-3 welding wire with a diameter of 1.2 mm. The substrate was 316L stainless steel plate. The laser power was 2200 W, the scanning rate was 30 mm / s, the wire feed rate was 36 mm / s, the hot wire current was 80 A, the laser focal length was 27 mm, the welding wire extension was 30 mm, the interpass temperature was 100℃, and the shielding gas was high-purity argon with a flow rate of 20 L / min.

4. The differentiated heat treatment method for Inconel 625 alloy based on the characteristics of deposited non-equilibrium microstructure using laser-fused wire forming, as described in claim 3, is characterized in that... The laser-fused Inconel 625 alloy has a deposited microstructure consisting of columnar crystals and cellular substructures epitaxially grown along the deposition direction. The primary dendrite arm spacing is 6-10 μm. Nb and Mo are enriched in the cellular boundaries and interdendritic regions, while Ni and Cr are mainly enriched in the dendrite nuclei. The interdendritic regions are accompanied by the precipitation of AB2-type Laves phase and MC-type carbides.

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