Research on Damage Evolution Laws and Life Prediction of 12Cr1MoVG Heat-Resistant Steel Under Different Thermal Shock Cycles

When a thermal power unit operates under deep peak shaving and variable load conditions, the heat-resistant materials of the boiler’s heat exchange surfaces will suffer accelerated fatigue damage due to frequent thermal shocks. To grasp the evolution law of thermal shock damage in high-temperature heat-resistant steel for the key equipment of thermal power units, based on the 12Cr1MoVG heat-resistant steel, a plastic strain simulation analysis was conducted. Through numerical simulation, the coupling relationship among thermal shock duration, thermal stress evolution, equivalent plastic strain (PEEQ) accumulation, damage penetration depth, and fatigue life was investigated. The results show that extending the duration of thermal shock will increase the thermal stress of the material, causing the failure depth to increase from 2.24 mm to 2.6 mm, and the accumulation rate of PEEQ at different depths of the material to accelerate, with the theoretical life decreasing from 1.82 × 105 cycles to 1.72 × 105 cycles. Extending the duration of low-temperature exposure will reduce the thermal stress of the material, causing the failure depth to decrease from 2.24 mm to 2.03 mm, and the accumulation rate of PEEQ at different depths of the material to slow down, with the theoretical life increasing from 1.81 × 105 cycles to 1.94 × 105 cycles. The research results can provide reference for fatigue damage and life assessment of the high-temperature and high-pressure materials used in key equipment of thermal power.