Creep-fatigue properties and life prediction method of new martensitic heat resistant steel

In this paper, the creep-fatigue properties of P92 and G115 new martensitic heat-resistant steels under load control are studied. Influence of dwell time and peak stress on the creep-fatigue properties under load control is analyzed. The results show that the creep-fatigue life decrease with the increase of peak stress and dwell time, and the creep-fatigue life of G115 steel is about 8-10 times that of P92 steel under the same peak stress, but G115 steel is more sensitive to the interaction between peak stress and dwell time. Changes in high temperature strength of materials lead to better creep-fatigue properties of G115 steel than P92 steel. Creep deformation and damage dominate creep-fatigue life during creep-fatigue under load control. For the creep-fatigue life prediction method under load control, the energy method, toughness exhaustion method, frequency separation method and frequency modified tensile hysteresis energy model are studied. Furthermore, based on the mechanism of load controlled creep-fatigue inelastic strain damage, the minimum cyclic creep rate method and the minimum creep rate method based on pure creep are proposed. The results show that the minimum cyclic creep rate model exhibited the highest prediction accuracy, and the method based on the minimum creep rate under pure creep predicts the high-life zone well, but the error in the low-life zone is relatively large.