喷丸强化对GH4096合金表面状态和疲劳性能的影响

The affect of Shot peening on surface state and fatigue performance of GH4096 alloy

摘要:

采用S110铸钢丸和Z300陶瓷丸对GH4096合金开展了喷丸强化试验，利用扫描电镜和三维轮廓仪分析了喷丸表面形貌，采用X射线衍射法分析了喷丸表面残余应力，采用金相显微镜和扫描电镜分析了喷丸试样的截面显微组织，并对喷丸试样进行了650℃低周疲劳试验。结果表明：随着喷丸强度的增大喷丸表面的粗糙度升高，相同喷丸强度下陶瓷丸喷丸表面的粗糙度低于铸钢丸喷丸强化的表面粗糙度。铸钢丸喷丸表面的残余压应力在-860MPa～-1000MPa之间，随着喷丸强度的增加残余压应力略有降低；陶瓷丸喷丸表面的残余压应力在-1000MPa～-1100MPa之间，随着喷丸强度的增加残余压应力略有增加。GH4096合金喷丸后表面发生塑性形变，形成弹丸坑形貌，出现晶界弯曲，产生晶格畸变，造成大量位错塞集，形成密集分布的小角度晶界，晶粒取向也随之改变。喷丸强化可提高GH4096合金650℃高温下的低周疲劳寿命，复合喷丸对疲劳寿命的提升效果最明显，相同喷丸强度下陶瓷丸的强化效果优于铸钢丸。喷丸强化后试样的疲劳裂纹多萌生于强化层之下的亚表面，喷丸强化的效果受表面粗糙度、残余应力及强化层深度等共同影响。

Abstract:

S110 cast steel shot and Z300 ceramic shot were used to do the shot peening experiment, the morphology of shot peening surface was observed by scanning electron microscopy (sem) and three-dimensional contour instrument. The residual stress of shot peening surface was tested by X-ray diffraction method, the microstructure of cross section of shot peening layer was analyzed by optical microscope(OM) and electron backscattered diffraction(EBSD). The reselut shows that with the increase of shot peening intensity the roughness of shot peening surface is increased. The roughness of ceramic shot peened surface is lower than that of cast steel shot peened. Residual compressive stress on the cast steel shot peening surface is between - 860 Mpa to -1000 Mpa and with the increase of shot peening intensity of residual compressive stress is slightly reduced. Residual compressive stress on the ceramic shot peening surface is between - 1000 Mpa to -1100 Mpa and with the increase of shot peening intensity of residual compressive stress is slightly insreased. After shot peening, projectile pits are formed on GH4096 alloy surface, plastic deformation occurs, grain boundaris are curved, lattice deformation appears, cause a lot of dislocation set and low angle grain boundaries, and the grain orientation changes. The 650 ℃ high temperature fatigue life of GH4096 alloy can improve by shot peening, double shot peening promotion of fatigue life is the most obvious, ceramic shot peening strengthen effect is better than that of cast steel shot. The strengthening effect of shot peening are mutual influenced by residual stress, surface roughness and depth of strengthening layer.