Ratcheting fatigue tests were carried out on the micro-alloyed 2.25Cr–Mo steel with variable mean stress (σ_m), stress amplitude (σ_a) and stress rate ($\dot{\sigma }$) at room temperature. Increase in the σ_m and σ_a resulted in higher plastic strain accumulation and caused a reduction in fatigue life; however, rise in the $\dot{\sigma }$ enhanced the fatigue life. Hysteresis loop analysis showed variation in plastic strain range under the different test variables. Transmission electron microscopy (TEM) was carried out to understand the lower plastic strain accumulation resulting from the high $\dot{\sigma }$. It was observed that at high $\dot{\sigma }$ there was formation of stacking-faults/micro-twins in the M₂₃C₆ carbides, due to which there was strain partitioning between the matrix and the carbide particles, consequently, the effective strain in the matrix was reduced. Using mathematical modeling, experimental fatigue life was predicted by the trial and error method. The predicted fatigue life was found within the 1.55X scatter band and there was a reasonable estimation of ratcheting fatigue life.

棘轮疲劳试验进行了对微合金化2.25Cr-Mo钢具有可变平均应力（σ_米），应力振幅（σ_一个）和应力速率（$\dot{\sigma }$） 在室温下。增加在σ_米和σ_一个导致较高的塑性应变的积累和造成的疲劳寿命的减少; 但是，$\dot{\sigma }$延长了疲劳寿命。磁滞回线分析显示了在不同测试变量下塑性应变范围的变化。进行透射电子显微镜（TEM）可以了解较高的塑性变形导致的较低塑性累积$\dot{\sigma }$。据观察，在高$\dot{\sigma }$在M ₂₃ C ₆碳化物中形成了堆垛层错/微孪晶，由于在基体和碳化物颗粒之间存在应变分配，因此降低了基体中的有效应变。使用数学模型，通过试错法预测了实验疲劳寿命。发现预测的疲劳寿命在1.55倍的散射带内，并且有合理的估计，即棘轮疲劳寿命。