Effect of Thermal Aging on the Intergranular Stress Corrosion Cracking Susceptibility of Type 310S Stainless Steel Journal Articles uri icon

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abstract

  • The effect of thermal aging on the intergranular stress corrosion cracking (IGSCC) susceptibility of Type 310S stainless steel was investigated. Samples were solution-annealed (baseline), sensitized (short-term aging), and thermally-treated (long-term aging) to form Cr-rich M23C6 carbides and sigma (σ) phase precipitate particles, respectively, on the grain boundaries. The thermal-aging heat treatments represent two limiting exposure conditions expected in-service for a fuel cladding in the Canadian Generation IV (supercritical water-cooled reactor) design concept and were considered to better understand the risk factors associated with an in-service IGSCC damage mode. The sensitized treatment exhibited the highest relative degree of sensitization (measured by double loop electrochemical potentiokinetic reactivation testing in 2 M H2SO4 + 0.01 M KSCN) and IGSCC susceptibility (measured by slow strain rate testing [SSRT] in a hot alkaline solution). The relative susceptibility reflects the controlling role played by Cr-depleted zones, which were only observed in the sensitized (short-term aging) material. The relatively large σ phase grain boundary particles in the thermally-treated (long-term aging) material preferentially cracked during SSRT, suggesting an apparent IGSCC susceptibility at the sample surface. However, the absence of Cr-depleted zones in this material prevented IGSCC from occurring, despite preferential cracking in the σ phase grain boundary particles. The dominant fracture mode in the hot alkaline solution was transgranular mixed-mode cracking. The implications of the results are discussed within the context of risk factors associated with an in-service IGSCC susceptibility in supercritical water.

publication date

  • April 1, 2018