Stress corrosion cracking resistance of martensitic stainless steels for transmutation applications
Abstract
The susceptibility of Alloy EP-823 to stress corrosion cracking has been evaluated using smooth and notched cylindrical specimens in neutral and acidic solutions at ambient and elevated temperatures using constant load and slow strain rate testing (SSR) techniques. C-ring and U-bend specimens have also been tested in the acidic solution. The effect of hydrogen on the cracking susceptibility has been evaluated under controlled cathodic potential. While no failures were observed with smooth specimens at constant load, the notched specimens showed failure. The SSR test results indicate that the true failure stress (sigmaf), time to failure and ductility parameters were gradually reduced with increasing temperature irrespective of the solution pH. The presence of a notch, however, enhanced the magnitude of sigma f. Neither C-ring nor U-bend specimens showed failure. Optical microscopy of the SSR specimen showed secondary cracking in the 90°C acidic solution. Fractographic evaluation by scanning electron microscopy revealed a combination of ductile (dimples) and brittle (intergranular/transgranular) failures.