Document Type: Research Paper
Department of Materials Science and Engineering, Faculty of Engineering, Shahid Chamran University, Ahvaz, Iran
Department of Materials Science and Engineering, Faculty of Engineering, Shahid Chamran University of Ahvaz, Ahvaz, Iran
Dissimilar metals friction welding of austenitic–martensitic stainless steels is commonly used in order to manufacture engine valves in the automobile industry. In this study, X53CrMnNiN219 (austenitic stainless steel) and X45CrSi93 (martensitic stainless steel) valve steel rods were welded by friction welding process. The welded joint was then heat treated at 760 0C for 60 min. Mechanical properties of the welded and heat treated samples were identified by means of microhardness and tensile tests. The microstructure of the weld and the fracture surface of the tension samples were investigated by optical microscopy and scanning electron microscopy. Fractographic evaluations also were performed by using scanning electron microscopy. According to the findings, due to the higher thermal conductivity and lower strength of the martensitic stainless steel, a larger upset and a broader heat affected zone is observed in the martensitic side. Furthermore, formation of non-tempered martensite with the maximum hardness of 880 HV in the heat affected zone (HAZ) of the martensitic stainless steel side makes as-welded material susceptible to brittle fracture as detected by fractographic examinations. Nevertheless, a successfully transition from brittle to ductile behavior is observed by the post-weld heat treatment at 760 0C for 60 min.