涡轮盘用IN718合金的高温低周疲劳及其裂纹扩展特性

研究了IN718合金在360℃、550℃和650℃下的低周疲劳行为及疲劳裂纹扩展速率da/dN,包括循环应力-应变行为、Massing效应、低周疲劳寿命的能量表达以及疲劳裂纹扩展速率,并讨论了保持时间对da/dN的影响。实验结果表明,该合金在各种温度下表现出循环软化,在本文所试温度下具有Massing特性,其塑性应变能与疲劳寿命在双对数坐标中呈现出很好的线性关系,其da/dN随温度的升高而增大,在650℃下保持时间对da/dN的影响很明显,而550℃时则很轻微。

LOW CYCLE FATIGUE AND FATIGUE CRACK GROWTH BEHAVIOR OF TURBINE DISK ALLOY IN718

The low cycle fatigue behavior and fatigue crack growth rate(da / dN) of alloy IN718 were studied in detail at the temperatue of 360℃ 550℃ and 650℃ , including the low cycle fatigue Δε / 2-2Nf curves, cyclic stress-strain behavior, Massing effect, the LCF lives expressed by plastic strain energy and crack growth, rates. The effect of hold time on da/dN was olso discussed.The experimental results show that this alloy appears cyclic softening at various temperature and has Massing characteristic at the test temperatuer, The relationship between plastic strain energy and fatigue life of alloy IN718 is the linear relations on double logarithm coordinate. From 360℃ to 550℃, the change of da / dN of allog 718 is slight, but the da / dN at 650℃ is much higher than that at 550℃. The effect of hold time on da / dN is obvious at 650℃, and the da / dN can be calculated by Equation(18) in this paper.