K403 nickel-based high-temperature alloy has excellent room temperature and high temperature comprehensive properties and is widely used in the manufacture of aircraft engine turbine blades and guide vanes. In order to solve the problems of crack defects caused by long-term service of turbine blades in complex working conditions, this work first compares the microstructure and tensile properties after repair by tungsten inert gas (TIG) welding and laser cladding, and then uses laser cladding to repair the blades and conduct non-destructive testing. OM and SEM are used to observe the microstructure and fracture morphology, and EDS is used to analyze the phase composition. The results show that the TIG welding repair process is prone to produce microcrack defects near the repair interface area, which are mainly caused by carbide phase and low melting point eutectic structure; the grains and structure of the laser cladding process repair area are more uniform, and the microcrack defects are easier to control; the comprehensive mechanical properties of the samples repaired by the laser cladding process are significantly higher than those of the samples repaired by the TIG welding process, and the laser cladding process has good process stability. The room temperature tensile strength of the TIG welding repair process is 69.22% of the strength of the K403 parent material, and the room temperature tensile strength of the laser cladding repair process reaches 87.44% of the parent material. The fracture morphology shows that the room temperature tensile fracture of the repair area shows mixed fracture characteristics, and the high temperature tensile fracture shows intergranular fracture characteristics. Microcracks, local liquid phase deficiency defects and carbides in the repair area are the main causes of tensile fracture. The laser cladding repair process has the advantages of concentrated heat source and small heat affected zone, which can effectively suppress defects in the repair area and refine the microstructure, and has greater advantages in blade repair. The laser cladding repair process was used to repair the edge plate crack damage caused by the blade test process. After fluorescence detection and kerosene-chalk detection, it met the relevant use requirements. Cast high-temperature alloy K403 is a nickel-based high-temperature alloy. Due to its good high-temperature strength, corrosion resistance, oxidation resistance, fatigue resistance and other characteristics, it is often used to manufacture important hot-end load-bearing structural parts such as turbine blades, guides, combustion chambers, turbine disks, compressors, guides, etc. In the actual service and application process, the hot-end load-bearing parts are in harsh working conditions such as high-temperature impact, high-temperature corrosion, and high-speed rotation for a long time. Fatigue cracks are prone to occur on the surface of the blades, which has a significant impact on the operation safety of the equipment. The replacement of hot-end load-bearing parts greatly limits the overall service life of the aircraft engine and increases maintenance costs. Advanced repair technology can repair damaged parts separately, which is conducive to shortening the manufacturing time cycle and reducing costs, and improving maintenance efficiency. The rapid repair process mainly consists of pre-treatment, material deposition, repair area processing, and post-treatment. Among them, the material deposition process is the key to the entire repair process. After the high-temperature material deposition of the repaired part, whether the mechanical properties and metallurgical bonding interface of the material in the repaired area can match those of the parent material is an important factor in evaluating the repair process and determining the performance.

At present, in view of the characteristics of small-area impact damage on the blade surface, mechanical processing is usually used to polish and remove the surface coating of the damaged area and complete the grooving. Tungsten inert gas (TIG) welding, brazing, electron beam welding, laser cladding and other processes are mainly used to melt the intermediate layer metal and complete the repair of the damaged part. TIG welding has the advantages of high heat input, concentrated heat source, good surface quality of the repaired area, no welding slag residue, low investment, and convenient operation. Song Wenqing et al. used TIG welding to study the repair process of high-temperature alloy turbine blades. The results showed that repair thermal cracks are the main defects of this process. Controlling process parameters such as current and high temperature time and reducing the formation of MC carbides are conducive to controlling the formation of repair thermal cracks. Ojo et al. studied the interface area of ​​the TIG welding process of nickel-based superalloy IN738. The results showed that the remelting and infiltration of the initial precipitated γ’ phase into the grain boundary was the main reason for the decrease in ductility in the welding area. At the same time, the continuous brittle eutectic structure and carbide phase in the interface area are also key factors for crack propagation in the welding failure process of nickel-based superalloys. Laser cladding repair has the advantages of small heat input, high control accuracy, good shape adaptability, narrow interface area, and small welding deformation. Its application in blade repair has also attracted the attention of domestic and foreign scholars. General Electric Company used Nd:YAG laser cladding to repair fatigue cracks in nickel-based superalloy gas turbines, and used shot peening to achieve fatigue resistance in the repair area. Richter et al. used laser cladding to complete the repair of Ti6242 titanium alloy integral blade disks. The results showed that the repair porosity of this process was low, and the tensile strength and fatigue strength exceeded the base material, which has the potential to further expand the application space. Lin Xin et al. used laser deposition repair technology combined with annealing + shot peening and other post-treatments to repair the fractured area of ​​TC4 titanium alloy blades and improve their performance. Liu et al. studied the ability of laser cladding technology to repair casting defects and holes in nickel-based high-temperature alloy gas turbine engine components. The study showed that the use of finer powder particles and fast laser scanning speed can effectively inhibit the generation of cracks in the interface area. Sheng Jiajin et al. studied the crack generation mechanism during the repair process of IN939 nickel-based high-temperature alloy blades. The results showed that the liquefied cracks and carbide phases formed in the heat-affected zone during the laser cladding process will cause local defects in the repair area. Kim et al.’s related research showed that the microcracks inside the blade repair area are the main reason for the decline in mechanical properties. Xu et al. used FeCrNiCu powder to complete the repair of thin-walled compressor impellers. The study showed that there were no defects such as slag inclusions and pores in the repair area. The relevant post-heat treatment process can reduce local defects to meet the service requirements.

In the actual service and application process, K403 nickel-based high-temperature alloy blades are in harsh working conditions such as high-temperature impact, high-temperature corrosion, and high-speed rotation for a long time, and fatigue cracks are prone to occur on the blade surface. Due to the advantages of maintenance cost, processing cycle, convenience, etc., manual TIG welding is still the main method in the actual production and repair of guide vanes. The laser cladding repair process is prone to poor fusion and pores in the repair area, and is rarely used in practice. At present, there are few reports on the comparative study of TIG welding and laser cladding to repair K403 cast nickel-based high-temperature alloy blades. In view of the long-term service of turbine engine blades under high temperature conditions, in order to verify the feasibility of laser cladding repair process in the repair process of guide vanes, this work uses TIG welding and laser cladding to repair K403 high-temperature alloy, and compares the microstructure and performance after repair.

1 Experiment and method

1.1 Experimental materials and equipment

The experimental base material is K403 cast high-temperature alloy, and the alloy chemical composition is shown in Table 1. The base material is heat treated according to the standard heat treatment specification before the experiment. The welding wire used for TIG welding and the deposition powder for laser cladding in the experiment are both nickel-based high-temperature alloy GH625, and its chemical composition is shown in Table 1. The diameter of the GH625 welding wire used in the TIG welding repair process is 1.2 mm, and the GH625 powder used in the laser cladding repair process is prepared by vacuum atomization method, and the average diameter of the powder is 53-106 μm.

Two different repair processes, TIG welding and laser cladding, were used for comparative study. Before repair, the surface of the specimen was polished with SiC sandpaper, and then ultrasonically cleaned and dried with acetone. The surface of the welding wire was polished to remove the oxide scale, and the cladding powder was vacuum dried for 3 h. The TIG welding repair scheme is based on the previous research and actual production application experience. The sample preparation uses the Fronius magicwave3000 welding machine. The main process parameters after optimization are: welding current 80 A, argon gas flow rate 10 L/min, welding speed 150-200 mm/min. In order to control the generation of thermal deformation and internal stress during the repair process, the entire repair process is carried out in a specific fixture, and the sample is air-cooled to room temperature after the repair is completed. The laser deposition cladding repair uses Arnold 6KW fiber laser 3D processing equipment, and the sample is prepared by coaxial powder feeding. The main components of the equipment include 6KW IPG YLS-6000 fiber laser, laser cladding head, powder feeder, work turntable, coaxial protective atmosphere and coaxial powder feeding head, etc., which can realize five-axis processing, with a spot diameter of 0.8 mm, a rated power of 800 W, a scanning speed of 600 mm/min, and a powder feeding rate of 0.8 g/min. To avoid oxidation of the sample during the repair process, the entire preparation process is carried out in high-purity argon gas, and then air-cooled to room temperature.

1.2 Sample preparation and test method

The schematic diagram of tensile specimen and laser cladding repair is shown in Figure 1. After the solder is filled into the groove pre-processed on the parent material, it is cut in the direction perpendicular to the weld. The sampling method is shown in Figure 1 (a). The tensile performance test is carried out on an electronic universal testing machine. The test is carried out on an MTS E40 tensile testing machine according to the standard GB/T 2652-2008 “Weld and Deposited Metal Tensile Test Method”. The tensile rate is 0.15 mm/min. Five parallel specimens are tested in each group, and the average value is taken as the final strength.

After the laser cladding repair is completed, the cutting is carried out in the vertical direction of the weld to cut out a 20 mm×10 mm×10 mm metallographic block. Sandpaper is used for grinding, mechanical polishing, and corrosion treatment to complete the metallographic specimen preparation. The JOEL 7610Plus field emission scanning electron microscope equipped with EDS is used to complete the microstructure observation and analysis of the repair area.

2 Results Analysis and Discussion

2.1 Macromorphology and Microstructure

Figure 2 shows the cross-sectional metallographic microstructure of the repaired steel using the TIG welding repair process. It can be seen that the interface of the repaired area is smooth and has a small number of random microcrack defects. From Figure 2 (a), it can be seen that the entire repaired area can be divided into the welding area, interface area, and parent material area according to the macroscopic morphology of the organization. The width of the interface area is about 400 μm. The microstructure of the welding area can be seen in Figure 2 (b). From Figure 2 (d), it can be seen that the microstructure of the K403 parent material area is characterized by a dendritic structure, mainly composed of γ phase, γ’ phase, (γ+γ’) eutectic phase and carbide. The γ’ phase and (γ+γ’) eutectic phase are distributed between the dendrites in the form of fine dots, and low-melting-point eutectic structures such as carbides are distributed between the grain boundaries. The microstructure of the interface area is shown in Figure 2 (c). It can be seen that under the influence of the heat source during the repair process, the cracks formed at the grain boundary extend from the parent material matrix into the interface area. The strengthening elements existing between the grain boundaries near the heat source further diffuse, and the continuous skeleton carbides are gradually transformed into discontinuous point carbides. The position where the cladding area is combined with the parent material is in the initial solidification state, and the undercooling caused by the composition and temperature is small, showing a layer of bright band on the bonding surface, forming a planar crystal structure. As the solidification process proceeds, the undercooling provided by the uneven composition causes the solidification structure to grow in the form of columnar crystals, growing from the parent material matrix to the heat flow direction, showing a distinct texture form. At the same time, the driving force provided by the uneven composition causes the columnar solidification liquid surface to develop on both sides of the growth direction to form dendrites. As the composition undercooling provided by the growth of dendrites on both sides increases, nucleation and crystallization occur inside the liquid phase to form an equiaxed crystal structure. Due to the large temperature gradient and rapid temperature drop in the cladding area, the organization in this area usually completes solidification nucleation in a non-equilibrium solidification manner and grows in a dendritic manner. Primary γ-Ni preferentially nucleates and grows, and γ’ phase and (γ+γ’) eutectic phase precipitate in the liquid phase or solid phase during solidification and exist between dendrites. The alloy strengthening elements in the remaining liquid phase combine with the C element during the cooling process, and finally form a low melting point eutectic structure such as carbide phase between grain boundaries.

Figure 3 shows the typical phase distribution of the parent metal area, cladding area and interface area of ​​the TIG welding repair process. EDS element analysis was performed on each phase, and the composition of each point is shown in Table 2. The cladding area contains a large amount of Ni and Cr elements, mainly in the form of γ solid solution, and a small amount of Al, Ti and other elements are diffused from the parent metal. Studies have shown that in GH625 alloy, when the Nb content exceeds 10% (mass fraction, the same below) and is less than 22%, a phase transformation reaction of L→γ+γ” will occur. The Nb content at point A is 13.77%. Combining the above research and the element content at point A, it can be seen that the phase composition of point A is γ+γ” (Ni3Nb). The typical micromorphology of the parent material K403 is shown at point B. According to the EDS results, this position contains a large amount of Al elements. The precipitated phase is γ’ (Ni3Al) phase. A large number of fine precipitates are dispersed in the γ matrix, which has the effect of precipitation strengthening. The typical microscopic morphology of the interface area is shown at point C. According to the EDS results, this phase contains a large amount of Al, Nb, Ti, Mo and other elements. The concentrated heat source input and high cooling rate during the repair process cause non-isothermal solidification behavior at the solidification interface, resulting in segregation of Al, Nb, Ti, Mo and other elements, forming a large amount of carbides. According to the EDS element analysis and related research of each area, the welding area of ​​the repaired structure using TIG welding process is composed of γ solid solution and γ”, the parent material area is composed of γ solid solution and γ’, and the interface area is composed of γ solid solution and carbide.

The metallographic microstructure of the interface repaired by laser cladding is shown in Figure 4. It can be seen that a bright boundary zone is formed at the bonding interface, and no defects such as holes, inclusions and thermal cracks are found. Compared with the TIG welding repair process, the interface area of ​​the laser cladding repair process is significantly narrowed to about 40 μm. The welding area shows a typical trend of fine dendrite epitaxial growth. In the cladding area far away from the parent material, the solidified metal is affected by the convective heat dissipation of the protective atmosphere and the heat transfer of the solidified metal.
The metal solidification is transformed from columnar crystal morphology to equiaxed crystal morphology. Due to the difference in heat source area and temperature gradient, compared with the microstructure of the welding area of ​​the TIG welding repair process, the laser cladding repair process has smaller grains and more uniform structure. As shown in Figure 4 (d), it can be seen that there are more carbides and low-melting-point eutectic phases between the grains of the K403 base material, which mainly increase the tendency of thermal cracks between the substrate and the cladding material during the repair process.

The element distribution in the interface area of ​​the two repair processes is shown in Figure 5. It can be seen that at a higher cooling rate, elements such as Nb, Mo, Ti, and W are segregated and enriched to form irregular block carbides. The two repair processes have a greater impact on the element distribution near the interface line. Each element diffuses more evenly near the interface of the TIG welding repair process, while there is an obvious concentration gradient near the interface of the laser cladding repair process. This result reflects that the thermal impact of the laser cladding repair process on the parent material is significantly smaller than that of the TIG welding repair process. The molten pool generated by the concentrated heat source of the laser spot is smaller, and the faster heat loss has less impact on the repair interface. The large heat input of the TIG welding repair process causes excessive thermal stress caused by shrinkage during cooling, making it easy to generate thermal cracks at the interface. At the same time, the large heat input easily dissolves the low-melting-point eutectic structure in the grain boundary again, resulting in cracking behavior. The impact of the laser cladding repair process on the repair interface area is significantly smaller than that of the TIG welding repair process, and the resulting grains and structure are more uniform, and defects are easy to control.

2.2 Mechanical properties analysis

The tensile specimens of the two repair processes were subjected to tensile tests at room temperature (20 ℃), 800 ℃, and 975 ℃, and the results are shown in Figure 6. As can be seen from Figure 6, the tensile strengths obtained by the laser cladding repair process are 787, 413, and 133 MPa, respectively, which are significantly higher than the tensile strengths of 623, 401, and 114 MPa obtained by the TIG welding repair process. The room temperature tensile strengths obtained by the laser cladding and TIG welding repair processes are 87.44% and 69.22% of the room temperature strength of the K403 parent material, respectively. The yield strengths of the two repair processes are relatively close, and with the increase of the ambient temperature, the yield strength shows a trend of continuous decline. In the high temperature tensile environment (800 ℃ and 975 ℃), the tensile strength of the joint is close to the yield strength, indicating that the tendency of the repaired area material to continue hardening after yielding is reduced. The room temperature elongation of K403 base material is 6%. The elongation changes of the two repair processes at different ambient temperatures are shown in Figure 6 (c). It can be seen that the elongation of the sample using the laser cladding repair process is slightly higher than that of the base material. The elongations of the samples with different repair processes at 975 ℃ are relatively close. According to the standard deviation of the elongation obtained by the two processes, it can be concluded that the dispersion of the tensile elongation data obtained by the TIG welding repair process is greater than that of the laser cladding repair process, which further shows that the stability of the laser cladding repair process is better than that of the TIG welding repair process.

The tensile strength, yield strength and elongation results of the two repair processes at three different temperatures show that the comprehensive mechanical properties obtained by the laser cladding repair process are more excellent. Combining the macroscopic morphology and microstructure of the repair area, it can be seen that the main reason for the difference in performance between the two may be that during the repair process, the laser cladding repair process has a smaller spot than TIG welding, the energy input is more concentrated, and the interface area and heat gradient generated are smaller, which makes the crack sensitivity in the bonding area between the solder and the base material lower. Therefore, the mechanical properties obtained by the laser cladding repair process are more excellent and stable.

2.3 Fracture behavior analysis

The K403 high-temperature alloy repair process is mainly used for the repair of engine blades. In order to study the influence law and mechanism of the repair process on its failure behavior, the fracture position and fracture morphology of the room temperature and high temperature tensile specimens of the repair process were analyzed. The fracture position statistics of the tensile specimens of the two repair processes are shown in Table 3. It can be seen that the fracture position of the specimens of the two repair processes is usually located in the parent material at room temperature, and the room temperature mechanical properties of the repair area can reach the same strength as the parent material. With the increase of the experimental temperature, the fracture of the specimen gradually shifts to the repair area, and the mechanical stability of the repair area decreases significantly. On the one hand, due to the defects such as microcracks and non-uniform precipitation inside the repair area, the high-temperature material softens and causes non-uniform deformation of the γ matrix and the low-melting point eutectic structure, which promotes the extension of microcracks and causes a sharp decline in performance. On the other hand, due to the difference in elastic modulus between the repair area and the parent material area, the connection interface area is prone to produce non-coordinated strain during the deformation process, resulting in an increase in failure behavior in the repair area. By comparing the effects of the two different repair processes on the fracture area, it can be seen that the laser cladding repair process is superior to the TIG welding repair process under all test conditions. Combined with the mechanical properties results, it can be seen that the mechanical properties of the laser cladding repair process are superior to the TIG welding repair process at room temperature and 800 ℃ because the former has a low risk of fracture in the repair area and the fracture position is biased towards the parent material area. At a high temperature of 975 ℃, since the fracture positions of both processes are located in the repair area, the mechanical properties of the two are similar.

The room temperature tensile fracture morphology of the two repair processes is shown in Figures 7 and 8. From the fracture morphology, it can be seen that it contains smooth and staggered cleavage steps, small dimples and unwelded defects, which belongs to a mixed fracture mode. Figure 7 (a) is the overall morphology of the room temperature fracture of the TIG welding repair process. It can be seen that the fracture surface is relatively flat and obvious crack characteristics can be observed. Figure 7 (b) is a local enlarged view. This area shows typical casting loose defect characteristics and is the crack origin area. The EDS results of points E and F are shown in Figure 7 (e), (f) and Table 4. It can be seen that this point is located near the interface area of ​​the cladding zone and is mainly composed of γ-Ni solid solution. There are a small amount of Al and W elements diffused. It is formed by the repair solidification of the weld material and the diffusion of the parent metal elements. The molten pool cooled and solidified too quickly during the repair process, and the dendrites were loosened due to the local rapid solidification of the insufficient liquid fluidity. The fracture morphology of Figure 7 (c) and (d) has a large number of fine quasi-cleavage fracture steps, river-like patterns and a small number of dimples, which have the typical characteristics of dendrite fracture. The fracture edge position of the part in Figure 7 (c) has obvious plastic deformation characteristics, and the fracture dimple zone mainly exists at this position. The fine and smooth quasi-cleavage fracture surface in Figure 7 (d) is mainly caused by the low-resistance path provided by a large number of brittle phases during the crack propagation process. Therefore, during the fracture process, the crack is generated from the loose defect position and continues to propagate along the intergranular brittle structure, and finally reaches the dense structure near the plastic deformation and propagates to the surface of the part.

Figure 8 (a) shows the overall morphology of the room temperature fracture of the laser cladding repair process. It can be seen that the defects in the fracture morphology are significantly less than those of the TIG welding repair process, and no obvious cracks are found. From Figure 8 (b), it can be seen that there are a large number of fracture dimples on the fracture surface. Figures 8 (c) and (d) are mainly characterized by mesh tear edges and local cleavage platform fractures, which are connected to form a mesh fracture pattern. The EDS results of points G and H are shown in Figures 8 (e), (f) and Table 4. There is a large amount of Nb and Mo element enrichment at point G, and the surrounding fracture surface is smooth. Microstructure analysis shows that this is a carbide phase formed by segregation at the grain boundary (Figure 8 (d)). During the fracture process, the carbide phase included at the grain boundary cracks and pulls out to form holes. Through the comparative analysis of the fracture morphology and mechanical properties of Figures 7 and 8, it can be seen that the plasticity of the specimen using the laser cladding repair process is significantly better than that of the TIG welding repair process.

The fracture morphology of the two repair processes at 800 ℃ high temperature tensile test is shown in Figure 9. Compared with the fracture morphology at room temperature, it shows obvious intergranular fracture characteristics. Comparing Figure 9 (a-1) and (b-1), it can be seen that the fracture edge of the sample using the laser repair process has typical plastic deformation characteristics. As can be seen from Figure 9 (a-2), there are a large number of dendrites and intergranular cracks on the fracture surface, which has the mixed fracture characteristics of intergranular fracture and transgranular fracture. The surface of the fracture along the dendrite is smooth and distributed with a large number of carbide phases, and the cross-sectional distribution of the transgranular fracture is partially ductile. As can be seen from Figure 9 (b-2), there are a large number of ductile dimples on the surface of the intergranular fracture, which belongs to the intergranular ductile fracture mode, and has the morphological characteristics of fatigue fracture bands and intergranular secondary cracks, indicating that this area has been subjected to long-term stress during the tensile process. By comparing the high-temperature fracture morphology of the two repair processes, it can be concluded that the grains and organization of the repair area using the laser cladding repair process are more uniform, and the ductile fracture characteristics are more obvious during the fracture process. In the process of crack propagation failure, a large number of dislocations are accumulated around the strengthening phase and fine carbide organization. The formation of a large number of dimples during deformation hinders the rapid expansion of cracks, which consumes more deformation energy during the fracture process. Combined with the high-temperature mechanical properties data above, the risk of liquefied cracks formed by the laser cladding repair process is reduced, and it has more advantages in high-temperature failure suppression.

According to the tensile fracture morphology of the two repair processes at room temperature and 800 ℃, it can be inferred that the defects such as insufficient liquid filling and microcracks generated during the repair process are the main causes of failure. The laser cladding repair process can effectively reduce repair defects, refine the organization of the repair area, produce greater plastic deformation during crack propagation, and improve the mechanical properties of the repaired specimen.

2.4 Blade repair

The process and actual effect of repairing blades by laser cladding repair process are shown in Figure 10. Figure 10 (b) shows the crack damage on the blade edge plate during the engine test. According to the crack direction and depth, a V-groove was first prepared in the repair area and manually polished. The repair area was about 5 mm, and then GH625 powder was used as the deposition powder for laser cladding repair. The effect after repair is shown in Figure 10 (c) and (d). It can be seen that there is no crack defect in the appearance after repair. Fluorescence detection is shown in Figure 10 (e), and no crack defect was found. After the surface of the blade repair area was manually polished and smoothed, visual inspection, fluorescence inspection and kerosene-chalk inspection were carried out, and no cracks and linear defects were found. After the repair product was assembled and tested, no cracks appeared in the weld and heat-affected zone, which shows that the blade can be repaired using this cladding powder and process.

3 Conclusions

(1) Both TIG welding and laser cladding can achieve metallurgical bonding between the welding material and the base material. The grain size of the repaired area after laser cladding is smaller and the structure is more uniform, and the width of the interface area is significantly reduced. Microcrack defects are prone to occur near the interface area when using the TIG welding repair process. The microcracks are mainly carbide phases and low-melting point eutectic structures.

(2) Comprehensive EDS element analysis of each area and related research show that the welding zone in the microstructure of the TIG welding repair process is composed of γ solid solution and γ”, the parent material zone is composed of γ solid solution and γ′, and the interface zone is composed of γ solid solution and carbide.

(3) The mechanical properties obtained by the two repair processes are quite different. The room temperature tensile strength of the laser cladding repair process and the TIG welding repair process are 87.44% and 69.22% of the strength of the K403 parent material, respectively. The tensile strength obtained by the laser cladding repair process is significantly better than that of the TIG welding repair process. The elongation after fracture of the laser cladding repair process is significantly higher than that of the TIG welding repair process, and is higher than the elongation after fracture of the parent material under room temperature. At the same time, the laser cladding repair process has higher stability in comprehensive mechanical properties and has higher repair quality.

(4) The room temperature fracture process of the two repair processes is mainly a mixed fracture mode. With the increase of temperature, the high temperature tensile fracture shows more obvious intergranular fracture characteristics. Compared with TIG The fracture of the samples of the welding repair process and the laser cladding repair process showed more obvious plastic deformation characteristics, which has greater advantages in suppressing the risk of liquefaction cracks, high temperature failure and blade repair applications.

(5) The laser cladding repair process was used to complete the repair of the edge plate crack damage caused by the blade test process. After fluorescence and kerosene-chalk detection, no cracks or linear defects were found, which met the repair requirements.