Microstructure and Mechanical Properties of the Friction Welded Joint between X۵۳CrMnNiN۲۱۹ and X۴۵CrSi۹۳ Stainless Steel

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, X۵۳CrMnNiN۲۱۹ (austenitic stainless steel) and X۴۵CrSi۹۳ (martensitic stainless steel) valve steel rods were welded by friction welding process. The welded joint was then heat treated at ۷۶۰ ۰C for ۶۰ 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 ۸۸۰ 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 ۷۶۰ ۰C for ۶۰ min.

Keywords:

Dissimilar metals welding , Friction welding , Heat treatment , Upset zone , X۵۳CrMnNiN۲۱۹ austenitic stainless steel