Effect of post-weld induction heat treatment on single-pass high-power laser-arc hybrid welded thick stainless steel clad plate: microstructure, mechanical properties and corrosion resistance

This study applied induction heat treatment to address insufficient ductility and localized corrosion resistance of (10 + 3) mm-thick Q235/304 stainless steel clad plates welds by single-pass high-power laser-arc hybrid welding. The effect of induction temperature on the microstructure, mechanical properties, and corrosion resistance of the welds was systematically studied, and the underlying mechanisms were analyzed. Results indicated that the microstructure of the as-welded joint's arc zone comprises austenite (A) and δ-ferrite (δ-F) with lathy, vermicular, and granular morphologies. The presence of δ-F adversely affects the weld's ductility and localized corrosion resistance. After induction heat treatment at 750–950 °C, the decomposition of δ-F into secondary austenite and M 23 C 6 carbides reduced stress concentration and crack initiation at the δ-F/A phase interfaces, significantly improving the ductility of the weld. Concurrently, the localized corrosion resistance of the welds initially decreased and then improved as the induction temperature increased. At 950 °C, the significant increase in the chromium (Cr) diffusion rate in the A phase effectively suppressed Cr segregation at the δ-F/A phase interface, leading to a remarkable improvement in localized corrosion resistance. Furthermore, the treated weld exhibited a tensile strength of 499 MPa, yield strength of 294 MPa, and elongation of 42.5 %, all meeting the standard requirements for the mechanical properties of the base material.