Crack propagation of CoCrFeNiTi-based multiprincipal element alloys formed by laser powder bed fusion in electrolytic hydrogen and high-pressure hydrogen gas environments

Abstract

The crack propagation behaviors of additively manufactured high-strength CoCrFeNiTi-based multiprincipal element alloy (MPEA) in electrolytic hydrogen and high-pressure hydrogen gas environments were investigated to understand the hydrogen embrittlement behaviors observed in slow strain rate tensile (SSRT) tests. Additive manufacturing of critical service components composed of high-strength and corrosion-resistant alloys is a revolution in the supply chain in the marine and energy fields. Among the critical specifications required for corrosion-resistant alloys in harsh environments, hydrogen embrittlement susceptibility is one of the most important criteria to be clarified. Two types of SSRT tests were conducted in electrolytic cathode charge and high-pressure (105 MPa) hydrogen gas environments to understand the crack propagation behaviors influenced by the hydrogen embrittlement of alloys. The SSRT test results demonstrated lower loss of ductility caused by hydrogen intake in the MPEA specimens than in the conventional nickel-based superalloy Alloy718. Transgranular crack propagation along dislocation slip bands and annealing twin boundaries with a precipitation-free zone was observed in the fractography analysis of the SSRT specimens after failure in the MPEA specimens. These findings imply that the dislocation mobility induced by diffused hydrogen in the crystal grains governs the hydrogen embrittlement susceptibility of CoCrFeNiTi-based MPEAs.