Hydrogen damage of nickel-base heat resistant alloys

The damage of nickel-base heat resistant alloys exposed to hydrogen at high temperature and pressure was investigated. Tested materials were mainly Inconel 600, Hastelloy X and nickel. Main results obtained are as follows: 1) Inconel 600 solution treated exhibited embrittlement due to the occluded hydrogen. 2) Hastelloy X solution treated did not exhibit embrittlement. 3) Nickel exhibited the irreversible damage although it was completedly dehydrogenated. 4) Stress concentration enlarged the susceptibility to embrittlement. Hastelloy X which did not show embrittlement in a smooth type specimen was also embrittled when stress was concentrated. 5) Embrittlement depended on Ni content and materials with higher Ni content exhibited the irreversible damage. 6) The susceptibility to hydrogen embrittlement of Inconel 600 and Hastelloy X increased when they were aged and carbides were precipitaed on grain boundaries. This effect could be explained by hydrogen trapping. (author)