The tensile and stress-controlled LCF tests of a powder metallurgy (PM) superalloy, Udimet 720Li have been conducted at 650 °C in order to investigate the effect of shot peening (SP) on notched low cycle fatigue (LCF) performance. The measurements of surface tomography, Micro-Vickers hardness, residual stress and failure mechanism analysis were conducted in detail. The results show that there are many regularly shaped machining traces on as-received (AS) surface while lots of highly disorganized dimples are mainly distributed on SP surface. A larger microhardness gradient is produced along the path from SP surface to the bulk of material compared with AS specimen. The maximum compressive residual stress of SP specimen is not more located at surface like AS one but at a depth of approximately 50–90 μm from surface. Compared with the applied stress, the effective stress curve of SP specimen becomes “flat” and the effective stress gradient decreases accordingly. The LCF lifetime of the notched specimen is significantly improved after SP process and the LCF lifetime increment is between 2.05 and 7.66 times. Finally, there are obvious differences on the failure mechanisms, such as fatigue crack initiation, propagation and final fracture between AS and SP specimens.

为了研究喷丸强化（SP）对缺口低周疲劳（LCF）性能的影响，已经在650°C下对粉末冶金（PM）高温合金Udimet 720Li进行了拉伸和应力控制的LCF测试。详细地进行了表面断层扫描，显微维氏硬度，残余应力和破坏机理分析的测量。结果表明，在接收到的（AS）表面上有许多规则形状的加工轨迹，而许多高度杂乱的凹痕主要分布在SP表面上。与AS试样相比，沿着SP表面到大部分材料的路径会产生更大的显微硬度梯度。SP样品的最大压缩残余应力并不像AS one那样更多地位于表面，而是距表面约50–90μm的深度。与施加的压力相比，SP试样的有效应力曲线变为“平坦”，有效应力梯度相应减小。SP处理后，带缺口样品的LCF寿命得到了显着改善，LCF寿命增加了2.05至7.66倍。最后，AS和SP试样之间的破坏机理存在明显差异，例如疲劳裂纹萌生，扩展和最终断裂。