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

• Published in: Archives of metallurgy and materials 2021-01, Vol.66 (4), p.1019-1022
• Main Authors: Ko, Seok-Woo, Park, Hyeonwoo, Yoo, Il, Kim, Hansoo, Lee, Joonho, Hwang, Byoungchul
• Format: Article
• Language: English
• Subjects: 347 stainless steel; Aging (metallurgy); confocal laser scanning microscope (clsm); fracture behaviour; Grain boundaries; High temperature; in-situ; Intergranular fracture; Laser beam welding; Niobium carbide; Solution heat treatment; Stainless steel; Stainless steels; Stress concentration; Tensile tests; welding
• ISSN: 2300-1909; 1733-3490; 2300-1909
• DOI: 10.24425/amm.2021.136417

In-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 M23C6 carbides were preferentially formed at grain boundaries after subsequent aging treatment. The M23C6 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 M23C6 carbides at grain boundaries.