Microstructure and properties of K403 nickel-base superalloy guide vane repaired by tungsten inert gas welding and laser cladding process

K403 nickel-base superalloy is widely used in the manufacture of aero-engine turbine blades because of its excellent properties at room temperature and high temperature. In order to solve the problem of turbine blade crack defects caused by long-term service in complex working conditions，in this work，two different processes of （tungsten inert gas，TIG） welding and laser cladding were used to repair the blade cracks，and the microstructure and properties of the repaired region were studied. The influence of TIG welding and laser cladding repairing on microstructure，mechanical properties and failure behavior was analyzed. The results show that the microcracks tend to occur near the repair interface using the TIG welding repairing process，which are mainly caused by carbides and low melting point eutectic structure. The grain and structure of the repaired area by laser cladding repair technology are more uniform，and the microcrack defects can be easier to control. The comprehensive mechanical properties of the samples repaired by laser cladding are obviously higher than those repaired by TIG welding repairing process，and the samples repaired by laser cladding have better process stability. The tensile strengths of the samples using the laser cladding repair process and the TIG welding repair process at room temperature have reached 87.44% and 69.22% of the strength of K403 base material，respectively. According to the failure analysis results，the tensile fracture at room temperature in the repaired region presents mixed fracture characteristics，and the tensile fracture at high temperature presents intergranular fracture characteristics. Microcracks in the repaired area，local liquid phase deficiency defects and carbide structure are the main reasons of failure. The laser cladding technology has the advantages of heat source concentration and smaller heat affected zone，which can effectively restrain the defects and refine the microstructure. Therefore，the laser cladding repair process is used to repair the edge plate crack damage generated during the blade test run. After fluorescence and kerosene-chalk detection，the repairing process meets the relevant reuse requirements.