Heat treatment process for regulating and controlling structure and performance of IN 625 alloy deposition layer

Abstract

The invention relates to the technical field of high-temperature alloy laser cladding repair manufacturing, and discloses a heat treatment process for regulating and controlling the structure and performance of an IN 625 alloy deposition layer. According to the method, the IN 625 alloy laser deposition layer is subjected to continuous heat treatment under a specific process, so that the deposition chromatography phase form and distribution and microhardness regulation and control are effectively realized, and a technical reference is provided for related employees to design and optimize the heat treatment process of the IN 625 alloy deposition layer.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of laser cladding repair manufacturing of high-temperature alloy, and particularly relates to a heat treatment process for regulating and controlling the microstructure and performance of an IN 625 alloy deposited layer. BACKGROUND

[0002] The IN 625 alloy is a solid solution strengthening type nickel-based wrought high-temperature alloy taking molybdenum and niobium as main strengthening elements, and is mainly applied to the manufacturing of aero-engine parts, aerospace structural parts and chemical equipment. The alloy takes Nb and Mo elements as main strengthening elements, and has the characteristics of high-temperature resistance, corrosion resistance, oxidation resistance and creep resistance. The IN 625 alloy has excellent tensile properties and fatigue strength in the range of-196-980 DEG C. As a widely used metal additive technology, the laser direct energy deposition technology (LP-DED) has the advantages of low cost, high deposition efficiency and high precision, and provides a new way for rapid manufacturing and repair of large metal parts, and has great application prospects in the fields of shipbuilding, mechanical manufacturing, aerospace and the like. At present, the IN 625 high-temperature alloy has been widely applied to the laser direct energy deposition manufacturing and repair process of high-temperature alloy components.

[0003] However, in the laser direct energy deposition process of the IN 625 alloy component, Cr, Nb and Mo elements contribute to the solid solution strengthening of the nickel matrix, and the generation of harmful phases will lead to the reduction of structural performance, thereby reducing the product quality, safety and reliability. The microstructure and performance of the IN 625 deposited layer have been one of the problems that the industry has been concerned about.

[0004] Therefore, it is of great significance to regulate and control the microstructure of the laser deposited IN 625 alloy, control the morphology and distribution of precipitated phases, and improve the mechanical properties and operation stability of the material component by designing and implementing a related heat treatment process. SUMMARY

[0005] In view of the limitations of the background art, the present application provides a heat treatment process for regulating and controlling the microstructure and performance of an IN 625 alloy deposited layer. The heat treatment of the laser deposited layer of the IN 625 alloy under a specific process effectively realizes the regulation and control of the morphology and distribution of precipitated phases and the microhardness of the deposited layer, and provides a technical reference for related personnel to design and optimize the heat treatment process of the IN 625 alloy deposited layer.

[0006] The specific technical scheme of the present application is as follows:

[0007] A heat treatment process for regulating and controlling the microstructure and performance of an IN 625 alloy deposited layer. The process comprises the following steps:

[0008] S1: preparing an IN 625 alloy component by laser direct energy deposition.

[0009] S2: heat treatment of the deposited layer of the laser direct energy deposition IN 625 alloy component.

[0010] S3: microstructure characterization and microhardness test of the deposited layer of the laser direct energy deposition IN 625 alloy component.

[0011] Preferably, the laser direct energy deposition IN 625 alloy component is prepared. Specifically, laser power, scanning rate, powder feeding rate and other process parameter combinations are set within a reasonable laser direct energy deposition process window to prepare the IN 625 alloy component.

[0012] Preferably, the laser direct energy deposition IN 625 alloy component is heat treated. Specifically, after the preparation of the laser direct energy deposition IN 625 alloy component is completed, the deposited component is subjected to heat aging, hot isostatic pressing and solid solution annealing treatment.

[0013] Preferably, the microstructure of the laser direct energy deposition IN 625 alloy component is characterized. Specifically, after the heat treatment is completed, the deposited layer metallographic sample is prepared for microstructure characterization and microhardness test.

[0014] The present application has the beneficial effect that by heat treating the IN 625 alloy laser deposited layer under a specific process, the microstructure of the deposited layer and the morphology and distribution of precipitates, microhardness can be effectively controlled, providing a theoretical basis and technical support for the optimization of the microstructure and performance of laser cladding IN 625 alloy parts. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 Microstructure morphology of the IN 625 alloy laser deposited layer (laser power = 400 W);

[0016] Figure 2 Microstructure morphology of the IN 625 alloy laser deposited layer after heat aging treatment (laser power = 400 W);

[0017] Figure 3 Microstructure morphology of the IN 625 alloy laser deposited layer after heat aging treatment + hot isostatic pressing + solid solution annealing treatment (laser power = 400 W);

[0018] Figure 4 Microstructure morphology of the IN 625 alloy laser deposited layer (laser power = 2000 W);

[0019] Figure 5 Microstructure morphology of the IN 625 alloy laser deposited layer after heat aging treatment (laser power = 2000 W);

[0020] Figure 6Microstructure of laser deposited layer of IN 625 alloy after heat aging treatment + hot isostatic pressing + solid solution annealing treatment (laser power = 2000 W). DETAILED DESCRIPTION

[0021] The application is further illustrated below with reference to specific examples

[0022] Example 1

[0023] Step 1: Preparation of laser direct energy deposition IN 625 alloy component. First, the laser direct energy deposition system mainly includes a laser, a cladding head, a powder feeder, a cooling system, a KUKA robot, and a control system. Argon gas with a purity of 99.9% is selected as the powder feeding and protective gas. The test substrate is K4002 nickel-based superalloy with a size of 150mm*150mm*8mm, and IN625 nickel-based superalloy powder is used as the filling material, with a powder size of 45-150μm. Before the test, the surface of the substrate is polished and cleaned to remove surface stains and oxidation film. The powder is dried by placing it in a vacuum drying oven at 120°C for more than 4 hours.

[0024] The deposition parameters are set as follows: laser power is 400 W, scanning speed is 10 mm / s, powder feeding rate is 150 g / s, and defocusing amount is -3 mm. The substrate plane is set as the X-Y plane, the laser beam is directed to the substrate and forms a molten pool in the Z direction, and the powder material is continuously added in the Z direction to form a deposited layer. Unidirectional scanning strategy is used for deposition, single pass cooling time is 5 s, single layer overlap rate is 35%, single layer lifting amount is 0.4 mm, and deposited layer size is 50mm*50mm*2mm.

[0025] Step 2: Heat treatment of laser direct energy deposition IN 625 alloy component deposited layer. First, the IN 625 alloy component is subjected to heat aging treatment, the sample is placed in a heat treatment furnace, the temperature is set to 1065°C, and the temperature is maintained for 90 minutes; further, hot isostatic pressing treatment is carried out, the temperature is set to 1163°C, the temperature is maintained for 4 hours, the internal pressure is 100 MPa, and then cooled to below 425°C; finally, solid solution annealing treatment is carried out, the temperature is set to 1177°C in a vacuum state, the temperature is maintained for 4 hours, and then cooled to below 649°C in air.

[0026] Step 3: Microstructure characterization and microhardness test of laser direct energy deposition IN 625 alloy component deposited layer.

[0027] After the laser direct energy deposition IN 625 alloy component deposition and heat treatment are completed, the metallographic sample of the deposited layer is prepared through mechanical cutting, inlaying, grinding, polishing, etching and other processes, and the cladding sample is cut into individual blocks using wire electrical discharge machining. Then grind with different grades of sandpaper from coarse to fine, polish with diamond polishing paste, and electro-etch with 10% phosphoric acid reagent solution. The microstructure morphology of the metallographic sample is observed and characterized by optical microscopy (OM) and scanning electron microscopy (SEM). The microhardness is measured on the deposited layer interface at an interval of 0.1 mm using a microhardness tester (HXS-1000AC type, double indenter microhardness tester). The load is 300 gf (1 gf = 9.8 mN) when loading, and the load is maintained for 10 seconds. The microhardness experiment is carried out at 10 different points, and the average value is taken as the final value. Draw and measure the straight line on the microscope image using ImageJ software. Count the number of grain boundaries intercepted, and at least 100 grain boundaries are intercepted for calculating the grain width measurement value.

[0028] Example 2

[0029] Step 1: Laser direct energy deposition IN 625 alloy component preparation. First, the laser direct energy deposition system mainly includes a laser, a cladding head, a powder feeder, a cooling system, a KUKA robot, and a control system. Argon gas with a purity of 99.9% is selected as the powder feeding and protection gas. The test substrate is K4002 nickel-based superalloy with a size of 150mm*150mm*8mm, and IN625 nickel-based superalloy powder with a particle size of 45-150μm is used as the filler material. Before the test, the surface of the substrate is polished and cleaned to remove surface stains and oxidation film. The powder is dried by placing it in a vacuum drying box at 120°C for more than 4 hours.

[0030] The deposition parameters are set as follows: laser power is 2000W, scanning speed is 10mm / s, powder feeding rate is 150g / s, and defocusing amount is -3mm. The substrate plane is set as the X-Y plane, the laser beam is directed to the substrate and forms a molten pool in the Z direction, and the powder material is continuously added in the Z direction to form a deposited layer in the beam direction. Single-scan strategy is used for deposition, single-pass cooling time is 5s, single-layer overlap rate is 35%, single-layer lifting amount is 0.4mm, and deposited layer size is 50mm*50mm*2mm.

[0031] Step 2: Heat treatment of the IN 625 alloy component deposited by laser direct energy deposition. First, the IN 625 alloy component was subjected to heat aging treatment. The sample was placed in a heat treatment furnace and the temperature was set to 1065℃ for 90 minutes. Next, hot isostatic pressing was performed at a temperature of 1163℃ for 4 hours under an internal pressure of 100MPa, followed by cooling to below 425℃. Finally, solution annealing was performed under vacuum at a temperature of 1177℃ for 4 hours, followed by cooling in air to below 649℃.

[0032] Step 3: Characterization of the microstructure and microhardness test of the deposited layer of IN 625 alloy components by laser direct energy deposition.

[0033] After laser direct energy deposition (LDED) of IN 625 alloy components and subsequent heat treatment, metallographic samples of the deposited layer were prepared through mechanical cutting, mounting, grinding, polishing, and etching. The clad samples were then cut into individual blocks using wire electrical discharge machining (EDM). These blocks were then ground with sandpaper of varying coarse to fine grades, polished with diamond polishing paste, and electro-etched with a 10% phosphoric acid solution. The microstructure of the metallographic samples was observed and characterized using optical microscopy (OM) and scanning electron microscopy (SEM). Microhardness was measured at 0.1 mm intervals on the deposited layer interface using a microhardness tester (HXS-1000AC type, dual-indenter microhardness tester). A load of 300 gf (1 gf = 9.8 mN) was applied and held for 10 seconds. Microhardness tests were performed at 10 different points, and the average value was taken as the final value. Straight lines were plotted and measured on the microscope images using ImageJ software. The number of grain boundaries intercepted was counted, with at least 100 grain boundaries intercepted, to calculate the measured grain width.

[0034] The metallographic microstructure of the sedimentary layer cross section obtained in Example 1 is as follows: Figure 1 As shown. After heat aging treatment, the metallographic microstructure morphology of the cross-section of the deposited layer is as follows. Figure 2 As shown, after heat aging treatment + hot isostatic pressing + solution annealing, the metallographic microstructure morphology of the cross-section of the deposited layer is as follows: Figure 3 As shown in Table 1, the average grain width and microhardness of the deposited layer under different laser energy input states were measured. Figures 1-3As shown in Table 1 and Table 2, when the laser power is 400 W, the microstructure of the deposited layer is mainly columnar dendrites with small dendrites distributed therein, the dendrites show irregular arrangement, the average grain width is 44 μm, and the average microhardness value is 265 HV; after heat aging treatment, the average grain width is 40 μm, and the average microhardness value is 229 HV; further, after heat aging treatment + hot isostatic pressing + solid solution annealing treatment, part of the grains recrystallize and grow, the average grain width is 64 μm, and the average microhardness value is 193 HV.

[0035] The cross-sectional metallographic microstructure morphology of the deposited layer obtained in Example 2 is shown in FIG. 2. Figure 3 After heat aging treatment, the cross-sectional metallographic microstructure morphology of the deposited layer is shown in FIG. 3. Figure 4 After heat aging treatment + hot isostatic pressing + solid solution annealing treatment, the cross-sectional metallographic microstructure morphology of the deposited layer is shown in FIG. 4. Figure 5 The average grain width and microhardness of the deposited layer under different laser energy input states are shown in Table 1. Figures 4-5 As shown in Table 1 and Table 2, when the laser power is 2000 W, with the increase of heat input, the grain size increases obviously, different density parallel needle-like structure is observed, the average grain width is 94 μm, and the average microhardness value is 248 HV; after heat aging treatment, the average grain width is 63 μm, and the average microhardness value is 219 HV; further, after heat aging treatment + hot isostatic pressing + solid solution annealing treatment, part of the grains recrystallize and grow, the average grain width is 94 μm, and the average microhardness value is 188 HV.

[0036] Table 1 Average grain size and microhardness test results of the deposited layer under different laser energy input states

[0037]

[0038] The analysis of the results of the embodiments shows that the heat treatment process for regulating the microstructure and performance of the IN 625 alloy deposited layer can effectively regulate the microstructure and precipitated phase form and distribution and the microhardness of the IN 625 alloy deposited layer under different laser energy input conditions, can provide an important technical reference for the design and optimization of the heat treatment process of the IN 625 alloy deposited layer, and has important theoretical research significance and practical application value.

[0039] The above is only some embodiments of the present application, and is not any form of limitation of the present application. Any person skilled in the art, without departing from the scope of the technical solutions of the present application, according to the technical essence of the present application, any simple modification, equivalent replacement and improvement of the above embodiments, etc., still belongs to the protection scope of the claims of the present application.

Claims

1. A heat treatment process for regulating the microstructure and properties of IN 625 alloy deposited layers, characterized in that... The steps are as follows: S1: Laser direct energy deposition (LDED) was used to prepare IN 625 alloy components. The deposition parameters were set as follows: laser power 400-2000W, scanning rate 10mm / s, powder feed rate 150g / s, and defocusing amount -3mm. The substrate plane was set as the XY plane. The laser beam was directed to the substrate and formed a molten pool in the Z direction. Powder material was continuously added in the beam direction to form a deposition layer in the Z direction. A unidirectional scanning strategy was used for deposition. The single-pass cooling time was 5s, the single-layer overlap rate was 35%, the single-layer lift was 0.4mm, and the deposition layer size was 50mm*50mm*2mm. S2: Heat treatment of the deposited layer of IN 625 alloy components by laser direct energy deposition. First, the IN 625 alloy components are subjected to heat aging treatment. The sample is placed in a heat treatment furnace and the temperature is set at 1065℃ for 90 minutes. Next, hot isostatic pressing is performed. The temperature is set at 1163℃ for 4 hours and the internal pressure is 100MPa. Then, it is cooled to below 425℃. Finally, solution annealing is performed. Under vacuum, the temperature is set at 1177℃ for 4 hours and then cooled in air to below 649℃. S3: Microstructure characterization and microhardness testing of the deposited layer of IN 625 alloy components by laser direct energy deposition.

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