In-situ Observation of High-Temperature Fracture Behaviour of 347 Stainless Steel Subjected to Simulated Welding Process

In-sItu ObservatIOn Of HIgH-temperature fracture beHavIOur Of 347 staInless steel subjected tO sImulated WeldIng prOcessIn-situ study on the high-temperature fracture behaviour of 347 stainless steel was carried out by using a confocal laser scanning microscope (clSm).The welding microstructures of the 347 stainless steel were simulated by subjecting the steel specimen to solution and aging treatments.undissolved nbc carbides were present within grains after solution treatment, and m 23 c 6 carbides were preferentially formed at grain boundaries after subsequent aging treatment.The m 23 c 6 carbides formed at grain boundaries worked as stress concentration sites and thus generated larger cracks during high-temperature tensile testing.In addition, grain boundary embrittlement was found to be a dominant mechanism for the high-temperature fracture of the 347 stainless steel because vacancy diffusion in the cr-depleted zones enhances intergranular fracture due to the precipitation of m 23 c 6 carbides at grain boundaries.