Effects of the buttering layer and post-weld heat treatment on the mechanical properties of dissimilar welding T91 and 347H

The power sector has made significant progress in increasing energy efficiency and reducing fossil fuel emissions. Advances in boiler tubing and piping design, such as dissimilar-metal weld (DMW) joints for ferritic and austenitic stainless steels, have been crucial. This study focuses on the dissimilar welding of T91 and stainless steel 347H, examining the effects of the buttering layer and post-weld heat treatment (PWHT) temperature on the microstructure and mechanical properties. The buttering layer alters the chemical composition and microstructure in critical regions, such as the heat-affected and partially melted zones. PWHT further enhances the mechanical properties in the ferritic region. The best mechanical properties were observed when the buttered sample was heat-treated at 700 °C, resulting in high tensile strength and toughness, and reduced hardness in the T91 interface and heat-affected zone, from 344 HV to 264 HV. These findings can help engineers develop welding processes for DMW joints.