On the influence of temperature on the hydrogen embrittlement susceptibility of alloy 718

Hydrogen is susceptible to modify mechanisms of stress corrosion cracking of alloy 718 component structure elements in Pressurized Water Reactors (PWR), during service at temperatures from 80°C to 340°C. In order to study hydrogen embrittlement susceptibility of alloy 718, samples have been firstly cathodically charged in hydrogen in molten salts (NaHSO4, 46.5% wt. – KHSO4, 53.5% wt.) at 150°C. After charging, tensile tests were carried out at 80°C, 150°C and 300°C for a constant strain rate of 5x10-4s-1. Quantification of hydrogen embrittlement was performed by the analysis of rupture modes and elongation to failure. Rupture mode identification and tensile tests evidenced a maximal susceptibility to hydrogen embrittlement at 80°C whereas hydrogen effect was less noticeable at 300°C. From these results, the evolution of hydrogen location and interaction with deformation as a function of temperature was then discussed. (AU) © 2010 by The Materials, Metals, & Materials Society. All rights reserved.