High temperature fatigue resistance of an ACI HH50-type cast austenitic stainless steel

A study was undertaken to examine the high temperature low cycle fatigue behavior of an ACI HH50-type cast austenitic stainless steel. The samples were cast and machined into cylindrical specimens and then subjected to isothermal strain controlled fatigue tests at 500, 650, and 800 °C with total strain amplitudes from ±0.30% to ±0.80% at a strain rate of 3.3 × 10−4/s. The cyclic stress responses and fatigue resistances were analyzed by obtaining the fatigue parameters of both Basquin and Coffin-Manson equations. Additionally, a general superposition curve containing all of test temperatures was obtained using a modified fatigue equation based on the constitutive equation for the energy criterion of fatigue failure in terms of the thermally activated dislocation motions. The temperature dependent fatigue parameters that were obtained from this equation enables compare high temperature fatigue resistances of alloys. The ACI HH50-type alloy showed superior fatigue properties in comparison with the ACI HF30 and AISI 304 stainless stills.