Performance of Alloy 800H for High-Temperature Heat Exchanger Applications

The tensile properties of austenitic Alloy 800H have been evaluated at temperatures ranging from ambient to 1000 °C. The results indicate that the tensile strength was gradually reduced with increasing temperature. Between ambient temperature and 200 °C, the failure strain was reduced possibly due to the occurrence of dynamic strain aging followed by its enhancement at temperatures up to 500 °C. Alloy 800H did not exhibit any failure in an acidic solution at constant-load. However, the true failure stress in this environment was reduced at elevated temperatures under a slow-strain-rate condition. The magnitude of electrochemical potentials became more active with increasing temperature. A detrimental effect of more noble controlled potential on the cracking susceptibility was noted in terms of the true failure stress. A combination of ductile and intergranular brittle failures was seen in the primary fracture surface of the tested cylindrical specimens