Effect of low temperature on hydrogen-assisted crack propagation in 304L/308L austenitic stainless steel fusion welds

Abstract

• Measured crack growth resistance of welds at 223 K with 140 wppm H (gas charged). • H reduced fracture initiation toughness by >59% and altered fracture mode. • 223 K altered fracture mode but had no effect on J IC of precharged welds. • At 293 K, microcracks initiate at δ-ferrite, and ferrite governed crack path. • At 223 K, microvoids form at γ deformation band intersections near phase boundaries. Effects of low temperature on hydrogen-assisted cracking in 304L/308L austenitic stainless steel welds were investigated using elastic–plastic fracture mechanics methods. Thermally precharged hydrogen (140 wppm) decreased fracture toughness and altered fracture mechanisms at 293 and 223 K relative to hydrogen-free welds. At 293 K, hydrogen increased planar deformation in austenite, and microcracking of δ-ferrite governed crack paths. At 223 K, low temperature enabled hydrogen to exacerbate localized deformation, and microvoid formation, at austenite deformation band intersections near phase boundaries, dominated damage initiation; microcracking of ferrite did not contribute to crack growth.