In-situ measurement of internal stress distribution change of TT600 by energy-dispersive X-ray diffraction with white X-ray micro beam

Abstract

Under the primary conditions of a pressurized water reactor, the intergranular stress corrosion cracking susceptibility of a Ni based alloy is improved by chromium carbide precipitation in grain boundaries. The effects of chromium carbide precipitation treatments are explained by the grain boundary strengthening mechanism, the intergranular corrosion prevention mechanism, and so on. However, few studies have demonstrated these mechanisms, and the effects on intergranular stress corrosion cracking susceptibility are not completely understood. Therefore, for the purpose of demonstrating the change in the internal stress distribution with or without grain boundary carbide precipitation treatment in the 600 alloy, in situ measurements were performed in this study using the X-ray diffraction technique with the BL-28B2 beamline at the SPring-8 synchrotron radiation facility under tensile stress. The results confirmed that there is a difference in the strain distribution in grain boundaries and trans-grains. Intergranular stress corrosion cracking is suppressed by preventing stress concentration in grain boundaries owing to the carbides precipitated at the grain boundaries.