Characterization of alloy C-276 as a structural material for high-temperature heat exchangers

This investigation was focused on characterizing the high-temperature tensile behavior and corrosion susceptibility of nickel-based Alloy C-276, a leading structural material for heat-exchangers in nuclear hydrogen generation. The tensile properties, evaluated at different temperatures, indicate that both the yield strength and ultimate tensile strength were gradually reduced with increasing temperature. However, the ductility parameters were not significantly influenced by the testing temperature. While no failures were observed in stress corrosion cracking (SCC) tests in an acidic solution under a constant-load, the true failure stress (sigmaf) was significantly reduced under a slow-strain-rate condition using both smooth and notched specimens. The critical potentials, determined in a similar environment by an electrochemical method, became more active at the elevated temperature. Cracking was enhanced at anodic and cathodic applied potentials, showing reduced failure strain and sigmaf. The fractographic evaluations of the primary fracture surface revealed dimpled microstructures, indicating ductile failures