激光冲击强化和喷丸强化对FGH97高温合金疲劳性能的影响

Influence of Laser Peening and Shot Peening on Fatigue Properties of FGH97 Superalloy

对FGH97粉末高温合金进行激光冲击强化和喷丸强化,利用X射线应力分析仪测定强化层的残余应力,测定650℃下旋转弯曲疲劳性能,利用SEM观察分析疲劳断口特征。结果表明,2种表面强化方法都可以提高FGH97粉末高温合金的疲劳性能,但激光冲击强化比喷丸强化具有更深的残余压应力层和较好的表面粗糙度,且残余应力在高温疲劳载荷下的松弛较小,因此具有更好的强化效果;与未表面强化的试样相比,喷丸强化和激光冲击强化试样的疲劳裂纹源都出现在亚表面,而未强化试样的疲劳裂纹源则出现在表面。

Effects of laser peening and shot peening on fatigue performance of the powder metallurgical nickel-based FGH97 superalloy were investigated. Compressive residual stresses in the surface layer were determined by X-ray diffraction stress tester. The rotating bending fatigue test at 650 ℃ was used to compare the surface enhancement effects between laser peening and shot peening. Moreover, the fatigue fracture characteristics were observed by scanning electron microscope. The results show that both laser peening and shot peening can improve the fatigue property of FGH97, but laser peening has much better surface enhancing effect than shot peening due to deeper compressive residual stress layer and good surface roughness, and the compressive residual stresses induced by laser peening are more stable than the ones by shot peening under fatigue process at high temperature. Furthermore, the fatigue crack sources of both laser peened and shot peened specimens initiate at the subsurface, while the untreated at the surface.