Tensile and stress corrosion cracking behavior of ferritic-martensitic steels in supercritical water

Tensile and stress corrosion cracking behavior of ferritic-martensitic steels in supercritical water were studied in order to evaluate the suitability of these steels for supercritical water nuclear reactor concept. The ferritic-martensitic steels tested in this study consisted of T91, HCM12A, HT-9, weld T91, and weld HCM12A. A series of constant extension rate tensile (CERT) tests at a strain rate of 3 x 10(-7) s(-1) were conducted in supercritical water over a temperature range of 400-600 degrees C and pressure 24.8 +/- 0.07 MPa. CERT tests in argon and in supercritical water with 100 and 300 appb dissolved oxygen also were performed at 500 degrees C to compare the effect of environment. The results show that HT-9 exhibited the highest yield and maximum stresses, followed by HCM12A, and T91. The reduction in area of T91 is the highest, followed by HCM12A, and HT-9. Temperature has a great effect on tensile behavior of these steels. An increase in test temperature from 400 to 600 degrees C reduces the yield stress by similar to 50%. Both T91 and HCM12A weld steels exhibited a slightly lower yield and maximum stresses than the base steels. Increased dissolved oxygen in the water resulted in a significant reduction of ductility. Fractography showed that all of the specimens exhibited ductile rupture except for HT-9 that showed evidence of intergranular cracking. Intergranular cracking in HT-9 is affected by temperature and oxygen concentration in supercriticai water. (C) 2009 Elsevier B.V. All rights reserved.