SCC in hot water environment - comparison of SCC mechanisms of two bainitic steels

CrNiMoV and NiMnMo steels were tested to assess their sensitivity to environmentally assisted cracking in PWR and oxygen-enriched water. Slow strain rate tests revealed that in the two steels, stress corrosion cracks only develop in high-oxygen water below the yield point. The crack growth kinetics was examined by the rising displacement test on pre-cracked CT specimens. Stress corrosion cracking (SCC) was observed in the high oxygen conditions in both steels but the SCC crack growth mechanism seems to be dependent on the specimen type. Differences in the SCC mechanism were found by tensile tests and attempts at their elucidation were made by using optical microscopy, SEM, and electrochemistry. 1 tab., 7 figs., 3 refs