Microstructural evolution and mechanical properties ofTIG welded superalloy GH625
(Beijing Key Laboratory of Aeronautical Materials Testing and Evaluation, Beijing Institute of Aeronautical Materials, Aviation Industry Corporation of China, Beijing 100095, China)
Abstract: The tungsten inert gas welding (TIG) technique was employed to weld the nickel-based wrought superalloy GH625, and the microstructures, element distribution, grain boundary character and mechanical properties of the welded joint were investigated systematically. The results indicated that the welded seam was of austenite dendrite crystal structure and no obvious heat affected zone (HAZ) was observed. A number of precipitated δphases with homogeneous distribution were observed in the interdendritic region of the weld fusion zone. The abnormal phenomenon observed in the weld fusion zone of GH625, i.e., higher hardness and larger grain size compared with the base metal, may be attributed to the precipitated δ phase in the weld fusion zone. The higher tensile strength in the base metal was mainly attributed to the presence of more contents of fine grains and twin boundaries, while the lower elongation in the welded joint was mainly owing to the precipitated δ phase.
Key words: nickel-based wrought superalloy; TIG welding; microstructure; microhardness; tensile property