Investigation of microstructure and mechanical properties of dissimilar joints between AISI 321 stainless steel and X65 high-strength low-alloy steel

In the present study, a dissimilar joint was established between 321 stainless steel and X65 high-strength low-alloy steel by shielded metal arc welding process using 308 and 309 stainless steel electrodes as filler materials. Then, the structure, microstructure, hardness, and tensile properties of the joints were investigated. Results showed that austenite and delta ferrite phases developed in the structure of the joints. Microstructure characterization confirmed that the volume fraction of delta ferrite in the microstructure of 309 weld metal was higher than the 308 electrode weld metal. A ferritic+martensitic layer was formed at the interface of both weld metals and X65 steel. The hardness of 308 and 309 weld metals was 30% and 38% higher than the low alloy steel base metal, respectively. Tensile test results showed that the strength of the joint set up using 309 electrode was 1.5% higher and its elongation was 26% lower than the joint made by 308 electrode. In all specimens fractured occurred at the interface between the weld metal and the low alloy steel. A mixed ductile-brittle fracture mode was observed on the fracture surface of tensile test specimens.