While multiple studies on alloy 718 under conditions of hydrogen embrittlement exist, a complete understanding of the influence of microstructural particularities of alloy 718 has not been reached to date. To address this, a large research program dealing with the effect of precipitates on hydrogen diffusion, hydrogen trapping and decohesion was conducted.
This paper focuses on the effect of heat treatment and microstructure on the susceptibility of alloy 718 to hydrogen embrittlement. Using in-situ tensile testing under electrochemical hydrogen charging, it was found that the ageing temperature clearly has an effect on the susceptibility to hydrogen embrittlement. This can be explained by microstructural features. Several mechanisms including hydrogen-enhanced localised plasticity (HELP) have been identified contributing to the hydrogen embrittlement susceptibility of alloy 718.
A correlation between hardness on the resistance of alloy 718 to hydrogen embrittlement and SSC was not found.