Hydrogen sulphide stress corrosion cracking of 2.25Cr-Mo steel weldments

Abstract

Constant extension rate tensile (CERT) tests were performed to investigate the fracture characteristics of the A387 steel weldments in an H2S charging environment. The heterogeneous (HG) welds using a stainless steel ER309-16 as a filler metal displayed inferior mechanical properties. In the as-welded condition, the heat-affected zone (HAZ) with coarse-grained structures initiated the crack. The propagation proceeded within the diluted region along the fusion boundary, owing to the formation of martensite in that region. Both the untempered HAZ and the diluted region revealed a high susceptibility to hydrogen embrittlement. The precipitation of Cr-carbides along the fusion boundary was found after tempering at 690 °C for 1 h, creating a more favorable path for the crack growth. The homogeneous (HM) welds, which were made by using the equivalent composition alloy as a filler metal (ER9016-B3), revealed that the coarse-grained HAZ of the as-welded specimen caused premature failure in H2S. The tempered HM welds showed somehow improvement in strength and ductility in H2S, but the crack still initiated at the coarse-grained HAZ of a weld.