K4002 nickel-based high-temperature alloy plate laser cladding process based on in-light coaxial powder feeding

Abstract

The invention discloses a K4002 nickel-based high-temperature alloy plate laser cladding process based on in-light coaxial powder feeding, and is suitable for the field of additive remanufacturing. According to the technology, for the problems that a K4002 high-temperature alloy material is poor in weldability, cladding defects are caused by severe temperature changes in the laser cladding process, cladding layer forming control is difficult and the like, on the premise that the laser cladding technology is short in development period, high in material utilization rate and flexible to operate is not changed, the laser powder coupling mode is modified, and the welding performance of the K4002 high-temperature alloy material is improved. And reasonable laser power, scanning speed and powder feeding rate are matched, the morphology of a cladding layer is improved while a good droplet transition effect is obtained, the surface roughness of the cladding layer is small, good metallurgical bonding with a substrate is achieved, the mechanical property is excellent, and no obvious cladding defect exists. The method is of great significance in promoting the application and development of the coaxial powder feeding process in the laser in the field of additive repair of the hot end component of the nickel-based high-temperature alloy engine.

Description

Technical Field

[0001] The invention proposes a K4002 nickel-based high-temperature alloy laser cladding flat plate process based on coaxial powder feeding in the laser, belongs to the technical field of additive manufacturing, and is suitable for the repair process of hot end castings of aircraft engines. Background Art

[0002] The hot-end castings of aircraft engines are exposed to high temperatures, complex stresses, and harsh environments. Their performance level is a significant indicator of a model of engine and an important symbol of a country's aviation level. Precision casting is one of the important forming methods for high-temperature alloy turbine blades of aircraft engines. However, due to the structural complexity of the blade profile and inner cavity and the particularity of the metallurgical behavior of the material, initial defects such as near-surface shrinkage, sand stains, and cracks are prone to occur in the characteristic areas related to the casting structure. In addition, the hot-end components are repeatedly used for a long time in harsh environments such as high temperature, high pressure, oxidation, and corrosion, resulting in wear and cracks, which lead to premature scrapping of parts. Using advanced repair technology to repair hot-end castings can reduce the frequency of replacing parts, extend service life, and save expensive high-temperature alloy materials. It has great engineering application and research value.

[0003] At present, the repair of key components of the hot end of aircraft engines and gas turbines mainly includes: spray repair technology, fusion welding repair technology, brazing repair technology and laser cladding repair technology. Laser cladding repair technology is a process that uses laser as a heat source to melt the filler material (powder, wire or plate) and the substrate surface together to form a cladding layer that is metallurgically bonded to the substrate surface, thereby significantly improving its surface wear resistance, corrosion resistance, heat resistance and oxidation resistance. Compared with traditional additive technologies such as welding technology and thermal spraying technology, laser cladding has many advantages, such as small heat-affected zone, low dilution rate and good surface quality. In addition, laser cladding manufacturing technology also has the advantages of short development cycle, high material utilization, flexible operation and easy control, and can quickly repair damaged parts.

[0004] However, the addition of Al, Ti, Nb and other elements to the K4002 nickel-based high-temperature alloy itself significantly affects the weldability of the high-temperature alloy. At the same time, laser cladding is a non-steady-state, fast-heating and fast-cooling transient process, and the entire process is accompanied by heat transfer, mass transfer, and convection phenomena. The flow behavior of the laser cladding molten pool directly affects the morphology, internal metallurgical quality, and forming accuracy of the cladding layer. Therefore, in the actual laser cladding repair process of difficult-to-weld materials such as K4002, problems such as difficulty in controlling the morphology of the cladding layer, poor metallurgical bonding, and cracks are prone to occur, and the size of the cladding layer is often too small or too large, making it difficult to repair actual components for defects of various sizes in hot-end castings.

[0005] At present, the laser cladding repair process of difficult-to-weld alloys such as K4002 has not been well optimized, which to a certain extent restricts the development of laser cladding repair in the field of aircraft engine hot end casting repair. Summary of the invention

[0006] In view of the limitations of the background technology, the present invention proposes a K4002 nickel-based high-temperature alloy laser cladding flat plate process based on coaxial powder feeding within the laser, which can solve the problem of poor forming of the K4002 cast nickel-based high-temperature alloy repair cladding layer without changing the original performance of the laser cladding process, and obtain effective, continuous and uniform cladding layer forming, and has the advantages of high reliability and good flexibility.

[0007] The technical solution to achieve the purpose of the present invention is: a K4002 nickel-based high-temperature alloy laser cladding flat plate process based on coaxial powder feeding in the light, the steps are as follows:

[0008] Step 1: Pre-process the K4002 cast nickel-based high-temperature alloy plate by cutting, grinding and cleaning;

[0009] Step 2: Use K4002 cast nickel-based high-temperature alloy with a thickness of 10 mm as the substrate, and IN625 nickel-based high-temperature alloy with an average diameter of 0.1 mm as the powder; use laser as the welding heat source, the laser power is 800 W, the scanning speed is 6 mm / s, the powder feeding rate is 1.5 r / min, the defocus amount is -2 mm, the powder feeding tube diameter is 1.5 mm, the tube mouth is 30 mm from the plate, the protective gas is pure argon, and the flow rate is 15 L / min;

[0010] Step 3: Convert the Gaussian circular spot laser into a ring laser and change the position of the powder feeding nozzle so that it is located at the bottom center of the laser head;

[0011] Step 4: Change the light-powder coupling form so that the powder beam is located in the hollow position of the ring laser. During the cladding process, the light beam fully wraps the powder beam, which belongs to the light-powder coupling form;

[0012] Step 5: Appropriately adjust the cladding process parameters to ensure the stability of heat input during the cladding process and the metal filling amount of the cladding layer;

[0013] Step 6: After the laser cladding is completed, the macroscopic formation of the cladding layer and the metallographic morphology of the cross section are sampled and photographed;

[0014] Step 7: Perform Vickers hardness test on the vertical cladding layer.

[0015] The beneficial effects of the present invention are as follows: first, the intra-optical powder feeding device has only a single powder tube, which makes it easier to achieve powder convergence and true coaxiality between the powder tube and the laser beam, which can greatly improve the powder utilization rate and the quality of the forming surface. The intra-optical coaxial powder feeding method is used to change the driving force of the powder feeding, avoid the influence of gravity on the powder, and the direction of the powder feeding is always perpendicular to the molten pool. The powder is heated evenly and the change in the direction of the scanning speed will not change the area of ​​the light-powder coupling. The light-powder coupling has high precision, so a uniform and stable cladding layer can be obtained. The energy of the annular hollow laser is in the shape of a "crescent or saddle", and the energy is transferred to the edge. The energy distribution is more uniform and reasonable. On the one hand, the entire melt channel is melted more fully, improving the phenomenon of insufficient edge melting caused by the circular solid light spot; on the other hand, because the energy distribution is more uniform, the energy in the center of the molten pool is not too high, the temperature gradient inside the molten pool is reduced, and the convection movement is weakened, which effectively improves the "peak-shaped" melt channel caused by the circular solid light spot. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 Schematic diagram of laser cladding repair process

[0017] Figure 2 Surface morphology of cladding layer

[0018] Figure 3 Cross-sectional macroscopic morphology of the cladding layer

[0019] Figure 4 SEM image of the microstructure of the cladding layer

[0020] Figure 5 Hardness distribution of cladding layer DETAILED DESCRIPTION

[0021] The present invention is further described in detail below in conjunction with specific examples, and the steps are as follows:

[0022] Step 1: Use K4002 nickel-based high-temperature alloy as the plate, and process the sample to 200mm×200mm×10mm by wire cutting. Grind the surface of the substrate and perform ultrasonic cleaning before welding. Use acetone to wipe the surface of the base material to remove impurities such as surface oxides and oil stains.

[0023] Step 2: Use K4002 cast nickel-based high-temperature alloy with a thickness of 10 mm as the substrate, and IN625 nickel-based high-temperature alloy with an average diameter of 0.1 mm as the powder; use laser as the welding heat source, the laser power is 800 W, the scanning speed is 6 mm / s, the powder feeding rate is 1.5 r / min, the defocus amount is -2 mm, the powder feeding tube diameter is 1.5 mm, the tube mouth is 30 mm from the plate, the protective gas is pure argon, and the flow rate is 15 L / min;

[0024] Step 3: Convert the Gaussian circular spot laser into a ring laser and change the position of the powder feeding nozzle so that it is located at the bottom center of the laser head;

[0025] Step 4: Change the light-powder coupling form so that the powder beam is located in the hollow position of the ring laser. During the cladding process, the light beam fully wraps the powder beam, which belongs to the light-powder coupling form;

[0026] Step 5: Appropriately adjust the cladding process parameters to ensure the stability of heat input during the cladding process and the metal filling amount of the cladding layer;

[0027] Step 6: After laser cladding is completed, the plate is mechanically cut into 15mm×15mm×10mm metallographic samples. After inlaying, it is polished with 200, 800, 1200, and 2000 mesh sandpaper and polished with 0.5W polishing paste. The metallographic sample is then immersed in phosphoric acid for metallographic electrocorrosion, and finally the microstructure is observed by SEM scanning electron microscope.

[0028] Step 7: Use a Vickers hardness tester to test at 0.1mm intervals under a load of 300g and a holding time of 15s.

[0029] The surface morphology of the cladding layer obtained in the example is as follows Figure 2 The cross-sectional macroscopic morphology is shown in Figure 3 The cross-sectional microstructure is shown in Figure 4 As shown in Figure 2, the hardness test results of the cladding layer are as follows: Figure 5 As shown. Under the laser coaxial powder feeding cladding process, the process parameters are laser power of 800W, scanning speed of 6mm / s, powder feeding rate of 1.5r / min, and defocus of -2mm. The surface of the cladding layer shows high continuity and uniformity, without adhesion of unmelted powder. Under the protection of argon gas, there is no obvious oxidation on the surface, and no obvious defects such as notches appear. From the cross-sectional morphology, compared with the circular spot laser, the fusion line formed by the ring laser is relatively flat, the cladding layer has a molten width of 2.36mm, a residual height of 0.82mm, a forming coefficient of 9.4, a dilution rate of 24%, good forming, moderate size, and a good metallurgical bonding between the cladding layer and the substrate. No obvious internal defects such as pores, cracks, and unfused layers are observed. From the metallographic results, the cladding layer is composed of cellular crystals, columnar crystals, and planar crystals from top to bottom, and the heat-affected zone and the matrix are mainly γ phase, Y / γ' eutectic phase, and MC carbide. The microhardness is divided into three different areas from left to right, corresponding to the cladding layer (CL), heat affected zone (HAZ) and substrate, and the microhardness increases with the distance from the cladding layer surface. Among them, the average microhardness of the substrate is the highest, which is 405HV; the average microhardness of the cladding layer is 267HV.

[0030] The results of the examples show that the laser cladding process and parameters of K4002 nickel-based high-temperature alloy flat plate based on coaxial powder feeding in the laser can effectively solve the problems of forming difficulties and cracks in the laser cladding process of difficult-to-weld high-temperature alloys, improve the cladding effect while obtaining good cladding layer forming quality, and provide a process basis for multi-layer and multi-pass laser cladding repair of actual components. The present invention provides an important technical reference for promoting the development of laser additive repair technology and the wide application of laser additive repair in the field of high-temperature alloy additive remanufacturing, and has potential economic and social benefits.

[0031] The above description is only a partial embodiment of the present invention and is not a limitation of the present invention in any form. Any person familiar with the professional field, without departing from the scope of the technical solution of the present invention, according to the technical essence of the present invention, any simple modification, equivalent replacement and improvement made to the above embodiment still falls within the protection scope of the claims of the present invention.

Claims

1. A laser cladding process for K4002 nickel-based high-temperature alloy flat plate based on coaxial powder feeding in the laser, characterized in that Here are the steps: Step 1: Pre-process the K4002 cast nickel-based high-temperature alloy plate by cutting, grinding and cleaning; Step 2: Use K4002 cast nickel-based high-temperature alloy with a thickness of 10 mm as the substrate, and IN625 nickel-based high-temperature alloy with an average diameter of 0.1 mm as the powder; use laser as the welding heat source, the laser power is 800 W, the scanning speed is 6 mm / s, the powder feeding rate is 1.5 r / min, the defocus amount is -2 mm, the powder feeding tube diameter is 1.5 mm, the tube mouth is 30 mm from the plate, the protective gas is pure argon, and the flow rate is 15 L / min; Step 3: Convert the Gaussian circular spot laser into a ring laser and change the position of the powder feeding nozzle so that it is located at the bottom center of the laser head; Step 4: Change the light-powder coupling form so that the powder beam is located in the hollow position of the ring laser. During the cladding process, the light beam fully wraps the powder beam, which belongs to the light-powder coupling form; Step 5: Appropriately adjust the cladding process parameters to ensure the stability of heat input during the cladding process and the metal filling amount of the cladding layer; Step 6: After the laser cladding is completed, the macroscopic formation of the cladding layer and the metallographic morphology of the cross section are sampled and photographed; Step 7: Perform Vickers hardness test on the vertical cladding layer.

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