IN-617 is a superalloy of nickel, primarily used as tubes of superheater, re-heater and steam generator in nuclear core because of its excellent performance in that environment. However, during service the length of tubular components progressively increases due to tensile mean stress resulting from the asymmetric cyclic stressing and the components fail in much smaller number of cycles than that tested under symmetric loading (without tensile mean stress). The present investigation deals with cumulative plastic strain arising under different levels of mean stress (σ_m), amplitude of stress(σ_a), and rate of stress (\(\dot{\sigma }\)); and their effect on fatigue life. While the accumulation of permanent deformation enhances with rise in σ_m and σ_a and the number of cycles to failure (N_f) decreases, there is opposite effect of \(\dot{\sigma }\) the permanent strain is decreased from rise in \(\dot{\sigma }\) and cyclic life is enhanced. TEM analysis of tested samples showed variation in dislocation substructures developed under the different variables.

IN-617是一种镍的超合金，由于其在该环境中的优异性能，主要用作核芯中的过热器、再热器和蒸汽发生器管。然而，在使用过程中，由于不对称循环应力导致的平均拉伸应力，管状部件的长度逐渐增加，并且部件在比在对称载荷（没有拉伸平均应力）下测试的循环次数少得多的循环中失效。本研究涉及在不同水平的平均应力 ( σ _m )、应力幅值 ( σ _a ) 和应力率 ( \(\dot{\sigma }\)); 及其对疲劳寿命的影响。虽然永久变形的累积随着σ _m和σ _a的增加而增加，并且失效循环次数 (N _f ) 减少，但\(\dot{\sigma }\)的相反效果是永久应变从上升中减小在\(\dot{\sigma }\)中，循环寿命得到了增强。测试样品的 TEM 分析显示了在不同变量下形成的位错亚结构的变化。