Hydrogen Damage of Nickel-base Heat Resistant Alloys

Abstract

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. Inconel 600 solution-treated exhibited embrittlement due to the occluded hydrogen. Hastelloy X solution-treated did not exhibit embrittlement. Nickel remained the irreversible damage even after hydrogen was completely eliminated. Stress concentration enhanced the susceptibility to embrittlement for Inconel 600. Hastelloy X which did not show embrittlement in smooth specimen was also embrittled in notched specimen in which stress was concentrated. Degree of embrittlement depended on nickel content, and alloys with higher nickel content exhibited an irreversible damage. The susceptibility to hydrogen embrittlement of Inconel 600 and Hastelloy X increased when they were aged and carbides precipitated at grain boundaries. This effect could be explained by hydrogen trapping.