Accelerated environmentally-assisted crack initiation testing of additively manufactured 316L stainless steel in LWR environments: Results of an international Round-Robin initiative

Additive manufacturing (AM) processes are of raising interest for the nuclear industry. Characteristics of components produced by laser powder bed fusion (LPBF) may differ from conventionally manufactured components and their long-term performance in light water reactor (LWR) environments and susceptibility to environmentally - assisted cracking (EAC) needs to be assessed. Comprehensive in-kind Round-Robin test series have been performed by ten European laboratories to assess the feasibility of constant extension rate tensile (CERT) testing as an accelerated EAC initiation test method for LPBF 316L stainless steel in pressurized and boiling water reactor environments. Flat tapered tensile specimens, prepared by LPBF, were solution annealed or stress relieved and their surface was either ground or polished. The specimen surfaces were inspected for cracks and critical stresses for EAC initiation were calculated based on the location of the last crack on the tapered section. The assessment for EAC initiation revealed that the LPBF 316L showed a relatively low susceptibility to EAC in both environments, but nevertheless EAC was observed in most cases. Although still more research is needed, this Round-Robin exercise has indicated the feasibility of the proposed testing approach.