Effect of Cold Rolling on Stress Corrosion Cracking of Type 316L and Type 316 Stainless Steels in High Temperature Water

概要

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Stress corrosion cracking (SCC) susceptibility of commercial type 316L stainless steel (SS) and 316 SS hot rolled plates was examined by the creviced bent beam method in oxygenated high temperature water at 561 K. Asreceived type 316L SS and 316 SS showed the highest susceptibility to SCC at the cold rolling reductions of 10% and 20%, respectively. Aging treatment on type 316L SS had a beneficial effect of mitigating SCC, although the same aging treatment degraded SCC resistance of type 316 SS in a certain temperature range probably because of the combined effect of sensitization.The fracture surface of as-received and cold rolled type 316L SS and type 316 SS consisted mainly of inter-granular SCC with a small fraction of trans-granular SCC similar to those observed in the actual components. Heavily cold rolled Type 316 SS showed a large fraction of trans-granular SCC even in sensitized condition, suggesting that the heavy cold rolling formed active paths much sensitive to SCC than Cr depleted zone in crystal grains.It was suggested from SEM observation that the crack growth process on specimen surface would contain coalition of several smaller cracks to one larger crack in addition to the growth of each crack.
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