Experimental Study on Fatigue-Creep of P/M FGH96 Superalloy with Different Holding Time

不同保载时间下FGH96粉末高温合金疲劳-蠕变试验研究

¹ Department of Aviation Mechanical Engineering and Management in Qingdao Branch, Naval Aviation University, Qingdao 266000, China
² 91213 Troops of PLA, Yantai 264000, China

Received: 14 October 2019

Abstract

The fatigue-creep deformation characteristics and evolutions of microstructure of P/M superalloy FGH96 widely used for the turbine disc of an aero-engine were investigated experimentally. The low cycle fatigue-creep tests with different holding times were performed at 550℃. The influence of the holding time on the stress-strain curve, cyclic strain response, fatigue-creep life and damage mechanism were discussed. The results reveal that the holding time has a significant effect on the fatigue-creep deformation characteristics. As the holding time increases, the hysteretic energy of inelastic strain rises, the steady-state hysteresis curve shifts to the right and the envelope strain and the envelope strain rate increase. Fatigue-creep life decreases firstly exponentially and then stabilizes. The creep damage gradually plays a leading role. The fracture analysis indicates that the introduction of the holding time makes the section appear as a multi-crack source. The fracture mode changes from transgranular fracture to transgranular-intergranular mixed fracture. The slip bands and a small amount of dimples appear in the crack propagation zone and the dimple characteristics of the transient fracture zone are obvious.

摘要

对航空发动机涡轮盘的典型材料FGH96粉末高温合金不同保载时间下的疲劳-蠕变变形特性及微观损伤机理进行了试验研究。开展了550℃下不同保载时间的低周疲劳-蠕变试验，讨论了保载时间对FGH96合金应力-应变曲线、循环应变响应、疲劳-蠕变寿命及损伤机理的影响。结果表明：保载时间对FGH96合金疲劳-蠕变变形特性有显著影响，随着保载时间的增加，非弹性应变迟滞能增大，稳态滞回曲线发生右移，包络应变及包络应变率增加，疲劳-蠕变寿命先呈指数减小后趋于平稳，蠕变损伤逐渐起主导作用。断口分析表明：保载时间的引入使得断面呈现出多裂纹源特征，断裂模式由穿晶断裂向穿晶-沿晶混合断裂转变，裂纹扩展区存在滑移带及少量韧窝，瞬断区韧窝特征明显。