Microstructural characterization of dissimilar laser weld between austenitic and ferritic stainless steels

Abstract

The present work involved microstructural characterization of thin sheet dissimilar laser welds between type 304 austenitic stainless steel and stabilized 17% Cr ferritic stainless steel and their comparison with welds produced by autogenous gas tungsten arc welding (GTAW). Low heat input of laser welding (LW) effectively reduced the size of fusion zone (FZ) and heat affected zone (HAZ). LW with focused laser beam (LB), preferentially displaced towards austenitic stainless steel (ASS), produced FZ with uniform and highly refined microstructure. Using nitrogen as the shroud gas during LW with preferentially displaced LB towards ASS, brought about a significant microstructural change, i.e., the development of largely austenitic FZ. It marked a significant improvement over the coarse-grained FZ microstructure of the GTA weld that was comprised of large blocks of ferrite and martensite/retained austenite. Austenitic microstructure of laser weld will result in significant improvement in the ductility over that of dissimilar welds made by autogenous GTAW.