Corrosion and metallurgical behavior of alloy C-22 for high-temperature applications

Austenitic Alloy C-22 has been tested for evaluation of its tensile and corrosion properties under conditions relevant to the nuclear hydrogen generation process known as the sulfur-iodine cycle. The results of tensile testing indicate that this alloy may be capable of maintaining metallurgical stability and enhanced ductility at temperatures up to 600°C. The stress-corrosion-cracking data suggest that this alloy may not undergo cracking in an acidic solution at 90°C at constant-load, the true failure stress (of) was significantly reduced under a slow-strain-rate condition using both smooth and notched specimens. The magnitude of the critical potentials determined by a polarization technique became more active with increase in temperature. The application of anodic control potential resulted in enhanced cracking tendency of Alloy C-22 showing reduced ductility, failure time and sigmaf. The corrosion rate in a similar environment at 150°C was enhanced at longer test duration showing a nonlinear weight loss versus time relationship. The fractographic evaluations of the broken specimen by scanning electron microscopy revealed dimpled microstructure indicating a ductile failure.