Metallurgical and Microhardness Investigations of Ferritic Stainless Steel 409M Welds

Ferritic stainless steel 409M was MIG welded with austenitic stainless-steel wire 308L using commercially pure Argon as the shielding gas. Experiments planned were conducted using an automated welding unit for study of different aspects of the welds. One of the important aspects investigated viz. microstructural analysis in conjunction with microhardness survey is presented in this paper. Weld characteristics studied were presented on WRC-1992 diagram and Balmforth's diagram to give insight into the composition of the welds being investigated. Extensive microhardness survey covering all the three weld zones viz. weld bead, heat affected zone and base metal are presented that helped in analyzing microstructural studies carried out on the same samples. The photomicrographs and the microhardness analysis have revealed finer ferrite and martensite on the base metal side. Higher values of Cr /Ni and eq eq martensite start temperature along with less SFE (Staking fault energy) values resulted in the formation of increased amount of lath martensite in the fusion zone. Some typical photomicrographs and the related microhardness survey graphs are included in this paper for visual representation of the results.