Stress Corrosion Cracking of SUS316 Stainless Steel in High Temperature Water(Materials, Metallurgy & Weldability)

概要

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Effects of solution treatment temperature and sensitization time on stress corrosion cracking (SCC) have been studied on SUS316 stainless steel in high temperature water at 562K containing dissolved oxygen of 8ppm using a slow strain rate testing (SSRT) technique at 4.17×10^<-6>s^<-1> and 8.35×10^<-7>s^<-1>. The Strauss test (ASTM A262E) and the oxalic acid etching test (ASTM A262A) were used to determine the degree of sensitization and Huey test (ASTM A262C) and anode polarization test were used to determine the influence of step solution treatment on segregation of impurities at grain boundary. In the case of the specimens solution-treated at 1373K, M_<23>C_6 and Laves phases were many precipitated than that of the specimen solution-treated at 1573K. For the width of attacked grain boundaries, this trend was coincident. In high temperature water, intergranular corrosion was occurred owing to Cr depletion resulting from the precipitation of M_<23>C_6 and Laves phase at grain boundaries of sensitized specimens and then IGSCC was occurred at these attacked grain boundaries at the small amount of strain and load. IGSCC was propagated to TGSCC according to the increase of strain. It was considered that IGSCC hardly occurred owing to the decrease of Cr-depleted zone at grain boundaries resulting from the precipitation of Laves phases.
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