Comparison of stress corrosion cracking susceptibility of austenitic and ferritic stainless steels in small punch testing

Abstract

The small punch (SP) test technique combined with electrochemical measurements for irradiated miniaturized specimens has been developed to evaluate the resistance to stress corrosion cracking (SCC) and corrosion of fusion reactor structural steels in a water-cooled environment under irradiation. An apparatus developed for SP-SCC testing using small specimens in a high temperature and high pressure aqueous solution under applied potential conditions was successfully demonstrated in the comparison of SCC susceptibility between Type 304 austenitic and HT-9 ferritic stainless steels. The SP fracture energies necessary for SCC initiation measured from the load versus deflection curves were obtained as a function of the applied potential. The occurrence of susceptibility zones to SCC was observed at the corrosion potential and transpassive regions of sensitized Type 304 steel. Surface films were examined by scanning electron microscope, Auger electron spectroscopy and laser Raman spectroscopy. The relationship between the nature of surface films and SCC susceptibility is discussed.