某镍基粉末合金高温疲劳裂纹扩展行为与模型研究

High Temperature Fatigue Crack Growth Behavior and Model of a Nickel-Based Powder Metallurgy Superalloy

针对涡轮盘用某镍基粉末高温合金材料,开展了高温疲劳裂纹扩展试验,分析了环境温度、载荷比、紧凑拉伸(CT)试件厚度等因素对于疲劳裂纹扩展行为的影响规律,建立和评估了考虑影响因素的裂纹扩展速率模型。结果表明:随着温度的升高和载荷比的增大,疲劳裂纹扩展速率会显著增大,而CT试件厚度对于扩展速率的影响较小;通过观测断口截面发现,在500~700℃内,疲劳裂纹的扩展机制与温度之间没有显著关联,而在700℃下,高载荷比的条件使得裂纹扩展断面更为粗糙;提出了一种温度相关的疲劳裂纹扩展速率模型,可较好地描述不同温度下的疲劳裂纹扩展曲线;对比了Walker模型和Newman裂纹闭合模型的应用效果,发现Walker模型在描述不同载荷比下的裂纹扩展速率方面更为优秀。

The high temperature fatigue crack growth test of a nickel-based powder metallurgy superalloy material used in turbine disk was carried out. The influence of temperature, load ratio and Compact Tension(CT) specimen thickness on the fatigue crack growth behaviour was analysed, and the crack growth rate model considering the influencing factors was established and evaluated. The results show that the fatigue crack growth rate increases significantly with the increase of temperature and load ratio, and the thickness of CT specimen has little effect on the growth rate. By observing the fracture section, it is found that there is no significant correlation between the fatigue crack propagation mechanism and temperature in the range of 500 ~ 700℃,while the crack propagation section is rougher under the condition of high load ratio at 700℃. A temperature dependent fatigue crack growth rate model is proposed, which can better describe the fatigue crack growth curves at different temperatures. The application effects of Walker model and Newman crack closure model are compared. It is found that Walker model is better in describing the crack growth rate under different load ratios.