The effect of electrical hydrogen charging on the strength of 316 stainless steel

The effect of electrical hydrogen charging on the strength of 316 stainless steel specimens has been investigated in tensile tests at 223 K, and the i ncrease of yield stress and the decrease of total elongation were observed. These tendencies increase with increasing hydrogen content of the specimen s. This is considered to be due to hydogen-induced phase transformation fro m gamma (fcc) to epsilon (bcc), alpha (bcc), which was confirmed by X-ray d iffraction method. Hydrogen concentration was determined by elastic recoil detection (ERD) method, the maximum of which reached 40% near the surface r egion. Positron annihilation lifetime was also measured after electrical hy drogen charging; and a longer lifetime of about 300 ps was observed, which suggests the formation of microvoids in the specimens. (C) 2000 Elsevier Sc ience B.V. All rights reserved.