喷丸对一种单晶合金表面完整性和高温缺口疲劳性能的影响

Effect of shot peening on the surface integrity and notched fatigue properties of a single-crystal superalloy at elevated temperature

摘要:

研究了喷丸后单晶合金的表面完整性和高温缺口疲劳性能。喷丸后表面形貌采用白光干涉仪表征，扫描电镜，两个方向观察（平行于受喷表面和截面方向）高分辨透射电镜和电子背散射衍射分析，疲劳性能采用旋转弯曲疲劳模式表征。采用旋转弯曲疲劳极限表征了强化增益作用，并与喷丸显微组织建立联系。结果表明，在760℃到850℃区间，喷丸强化较原始加工状态的疲劳极限增益达到14.8%，主要原因是高密度的缠结位错、加工硬化和晶粒错配。此外，通过表面应力集中系数计算表明，即使在平均粗糙度Ra升高的基础上，喷丸强化后表面应力集中系数降低。

Abstract:

The surface integrity and notched fatigue property of a shot-peened single crystal superalloy were investigated. The surface texture of the peened material was determined using a white light interferometer, while the microstructural characterization was performed using a scan electron microscopy, high resolution transmission electron microscopy from the plane and cross-section view directions, micro-hardness tester and electron backscatter diffraction. The gains, expressed in term of high temperature fatigue limit, were established by rotating-bending fatigue tests and discussed in relation to the microstructure evolution in the shot peening states. This revealed that the beneficial effect provided by shot peening is more than 14.8% against as-machined in a temperature ranging from 760℃ to 850℃ because of the high-density tangled dislocation, cold work and disorientation. Furthermore, the stress concentration coefficient is reduced by the shot peening procedure while the average profile height Ra increases according to the calculation of the surface stress concentration.