Stress corrosion cracking and hydrogen embrittlement studies of austenitic and ferritic steels by small punch test

Abstract

A small punch (SP) testing apparatus using miniaturized specimens in high temperature and high pressure aqueous solutions was successfully developed to evaluate the resistance to stress corrosion cracking (SCC) and corrosion of candidate structural steels in water-coolant environment under irradiation. Anodic polarization curves of Type 304 austenitic and HT-9 ferritic stainless steels were measured in borate buffered solutions at 523 K and SP fracture initiation energies of stress corrosion were obtained as a function of potential and strain rate. SP-SCC tests using small specimens showed that sensitized Type 304 steel and SCC susceptibility at the regions of corrosion potential and passive potential. Since the result of SCC susceptibility evaluation obtained in the presented work was in fair agreement with that demonstrated by popular slow strain rate test (SSRT) using uniaxial tensile specimens, the SP-SCC test was proposed as one of the SCC testing methods using irradiated miniaturized specimens. The effect of hydrogen charging on SP fracture behavior of HT-9 steel was observed and the SP test was confirmed to be useful for the evaluation of the susceptibility of candidate ferritic steels to hydrogen embrittlement.