Study on Microstructure and Properties of K438 Alloy Joint by Argon Arc Welding with Co Based Wire
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 stripM23C6,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.
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