The QCr0.8 alloy used in the thrust chamber liner wall of the reusable liquid rocket engine is subjected to high-temperature fatigue and high-temperature creep loading. This work investigates the effect of fatigue-creep interaction (FCI) on the fatigue life of QCr0.8 alloy. Experimental results reveal accelerated cyclic softening and decelerated stress relaxation in the alloy under FCI conditions, attributed to creep deformation and stress amplitude growth. The damage evolution mechanism of FCI is revealed by the results of the energy dispersive spectroscopy (EDS) and scanning electron microscopy (SEM). The decrease in fatigue-creep life of the QCr0.8 alloy is attributed to the fracture of the outer surface oxide layer, as well as the coupling development of creep voids and secondary cracks. Finally, a new fatigue-creep life prediction model has been developed, taking into account the increase in plastic strain energy resulting from stress relaxation and creep deformation behaviors. The study results provide substantial theoretical justification for the utilization of QCr0.8 alloy in the thrust chamber wall of reusable liquid rocket engines.

中文翻译：

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蠕变对 QCr0.8 合金疲劳性能的恶化作用：损伤机制和疲劳蠕变寿命评估

可重复使用液体火箭发动机推力室缸套壁采用的QCr0.8合金承受高温疲劳和高温蠕变载荷。这项工作研究了疲劳蠕变相互作用（FCI）对 QCr0.8 合金疲劳寿命的影响。实验结果表明，在 FCI 条件下，合金中的循环软化加速，应力松弛减速，这归因于蠕变变形和应力幅增长。能量色散谱（EDS）和扫描电子显微镜（SEM）的结果揭示了FCI的损伤演化机制。 QCr0.8合金疲劳蠕变寿命的降低归因于外表面氧化层的断裂以及蠕变空洞与二次裂纹的耦合发展。最后，开发了一种新的疲劳蠕变寿命预测模型，考虑到应力松弛和蠕变变形行为引起的塑性应变能的增加。研究结果为QCr0.8合金在可重复使用液体火箭发动机推力室壁中的应用提供了重要的理论依据。