采用RPL50型动蠕变试验机对P92钢进行630℃和不同应变幅下的低周疲劳试验，研究了P92钢的高温低周疲劳行为；基于塑性应变能密度与硬度、应力幅和低周疲劳寿命的关系，采用基于能量的硬度法对其低周疲劳寿命进行预测，并与试验结果进行对比。结果表明：P92钢是一种循环软化材料，其初始归一化应力幅随应变幅的增加而增加，且不同应变幅下的归一化应力幅均随循环周次的增加而降低；随着应变幅的增加，弹性应变幅保持稳定，塑性应变幅近似线性增加，软化率也相应增加，并最终稳定在0.3左右；硬度与应变幅满足良好的线性关系；基于能量的硬度法可以较准确地预测P92钢在630℃时的高温低周疲劳寿命，计算得到的预测寿命均位于试验寿命的±1.5倍标准偏差内。

Low cycle fatigue test was conducted on P92 steel with RPL50 dynamic creep tester at 630℃ and different strain amplitudes, and the high temperature low cycle fatigue behavior of P92 steel was studied. Based on the relationship between plastic strain energy density and hardness, stress amplitude and low cycle fatigue life, low cycle fatigue life of P92 steel was predicted by energy-based hardness method, and compared with the test results. The results show that P92 steel was a cyclic softening material. The initial normalized stress amplitude increased with the increase of strain amplitudes, and stress amplitude decreased with the increase of cycles at different strain amplitudes. With the increase of strain amplitude, the elastic strain amplitude remained stable; the plastic strain amplitude increased approximately linearly; softening rate increased and was stable at about 0.3 finally. There was a good linear relationship between hardness and strain amplitude. The energy-based hardness method could accurately predict the high temperature low cycle fatigue life of P92 steel at 630℃, and the calculated predicted lives were all within ±1.5 times standard deviation of test lives.