Thermomechanical Fatigue Behavior of a Reduced Activation Ferritic-Martensitic Steel

Thermomechanical and isothermal fatigue behaviour of a Reduced Activation Ferritic−Martensitic (RAFM) steel have been investigated under in−phase (IP) and out−of−phase (OP) conditions using different temperature ranges. OP TMF yielded the lowest lives compared to both IP TMF and isothermal fatigue (IF) cycling at the maximum temperatures (Tmax) in all the three temperature ranges. It was thus observed that the traditional design practice that relies on IF testing at the Tmax is bound to be nonconservative for the above steel, which could lead to adverse consequences on structural integrity. The results obtained are rationalised and discussed based on the detailed microstructural observations.