Embrittlement and localized corrosion in alloy Ht-9

Sudheer Sama, University of Nevada, Las Vegas


This investigation is focused on the evaluation of stress corrosion cracking (SCC), hydrogen embrittlement (HE) and localized corrosion susceptibility of alloy HT-9 in neutral and acidic solutions at 30, 60 and 90°C. Constant-load and slow-strain-rate (SSR) testing techniques were used to evaluate the SCC and HE behavior of this alloy by using smooth and notched tensile specimens. Hydrogen effect on the cracking behavior was evaluated by applying cathodic (negative) potential to the test specimens. Localized corrosion susceptibility was evaluated by cyclic potentiodynamic polarization technique. The results of constant load SCC testing showed a threshold stress at 80% of the material's yield strength value in the 90°C acidic solution. Reduced ductility and true failure stress were observed in the SSR tests due to the combined effect of acidic pH and increased temperature. SCC testing under cathodic charging showed further reduction in ductility and true failure stress. Polarized specimens showed pitting in the acidic solution. Fractographic evaluations by scanning electron microscopy revealed ductile and brittle failures, respectively in the neutral and acidic environments.