In this investigation, response of Alloy 617 M to creep-fatigue interaction loading has been studied. The creep-fatigue interaction tests were conducted in air environment at a constant strain rate of 3 × 10⁻³ s⁻¹ and strain amplitude of ± 0.4% with hold periods of 1 min, 10 min and 30 min at peak tension or compression at 973 K. The material showed initial hardening to a saturation followed by reduction in stress initiated by crack nucleation, propagation and final failure. The fatigue life decreased in presence of hold period. The decrease in fatigue life was more in tensile hold than in compressive hold. The fatigue life showed saturating trend for higher hold periods. Fractographic studies revealed significant intergranular creep cavitation under tensile hold whereas compressive hold exhibited transgranular fatigue striations in association with intergranular creep cavitation. Significant stress relaxation was found to take place during hold and was more in compressive hold than under tensile hold. The creep and fatigue damage have been assessed based on linear damage summation rule. Creep damage fraction was assessed from the stress relaxation considering the average stress, minimum stress and integrated stress over the relaxation curve. The creep-fatigue damage assessment considering integration of creep damage during stress relaxation showed most conservative compared to the other two approaches.

在这项研究中，已经研究了617 M合金对蠕变疲劳相互作用载荷的响应。蠕变-疲劳相互作用测试在空气环境中以3×10 ^-3 s ^-1的恒定应变率进行应变振幅为±0.4％，在峰值张力或973 K压缩时的保持时间分别为1分钟，10分钟和30分钟。材料显示出最初的硬化至饱和，然后由于裂纹成核，扩展和最终破坏而引起的应力降低。在保持期间，疲劳寿命降低。疲劳寿命的减少在拉伸保持力上比在压缩保持力上更大。疲劳寿命在较高的保持时间内呈现出饱和的趋势。断口研究显示，在拉伸保持下，颗粒间的蠕变空化作用显着，而压缩保持下，与颗粒间的蠕变空化作用相关，则表现出跨晶的疲劳条纹。发现在保持期间发生了显着的应力松弛，并且在压缩保持中比在拉伸保持下更多。蠕变和疲劳损伤已根据线性损伤求和规则进行了评估。从应力松弛评估蠕变损伤分数，考虑松弛曲线上的平均应力，最小应力和积分应力。考虑到应力松弛过程中蠕变损伤的综合考虑，蠕变疲劳损伤评估显示出与其他两种方法相比最为保守。