In-Situ Measurement of the Internal Stress Distribution Change of TT600 by Energy-Dispersive X-ray Diffraction with White X-ray Micro Beam

Under pressurized water reactor primary conditions, the intergranular stress corrosion cracking susceptibility of Ni base alloy is improved by chromium carbide precipitation in the grain boundaries. The effects of chromium carbide precipitation treatments are explained by the grain boundary strengthening mechanism, the intergranular corrosion prevention mechanism, and so forth. However, few studies demonstratate these mechanisms, and the effects on intergranular stress corrosion cracking susceptibility are not completely understood. Therefore, for the purpose of demonstrating the internal stress distribution change with or without grain boundary carbide precipitation treatment in alloy 600, in-situ measurments using the X-ray diffraction technique at BL28B2 of SPring-8 applying tensil stress were carried out. The results confirmed that there is a difference in the strain distribution in grain boundaries and inner grains. Intergranular stress corrosion cracking is suppressed by preventing stress concentration in grain boundaries due to carbides precipitated at grain boundaries.