Abstract: Aiming at repair requirements for wear of a gas turbine power turbine rotor blade,using Co based welding wire as the surfacing material,which matches with the thermophysical properties of the K438 cast nickel-based superalloy and has good compatibility,the argon arc welding process study was carried out to explore a new method to solve the cracking of high Al and Ti superalloys during fusion welding by changing preheating temperature and surfacing trajectory. The studies show that a combination of preheating and back and forth swinging perpendicular to the welding direction can produce crack-free butt joints. The surface of the prepared crack-free joints is well formed,the welding area and the substrate are well metallurgically combined,and Cr-rich strip M₂₃C₆,petal-shaped W element solid solution strengthening products and Cr-rich special-shaped M₆C phases with different shapes are dispersively distributed in the Co based matrix. In addition,the heat-affected zone of the joint has a hardening phenomenon,the highest hardness can reach 462 HV0.5,the hardness of the welding zone is about 263 HV0.5,and the average tensile strength of the joint is 472 MPa,which is 53%of the substrate.