The effect of hydrogen in 18-8 austenitic stainless steel

in which the Ni content is different

has been studied by positron annihilation lifetime and Doppler broadening. The result shows that the mean life increases as the time of hydrogen charge on the sample is prolonged. The mean lifetime of the sample charged with hydrogen for long time is about 9% as long as that of the sample uncharged with hydrogen. The change of S line-shape parameter of Doppler broadening with the time of charge presents a similar tendency. The Ni content of the sample appears no obvious effect on the quantities mentioned above. The state and the action of hydrogen in such steel have been discussed.