GH4169高温合金车削表面完整性对疲劳性能的影响

Effect of Surface Integrity of Turned GH4169 Superalloy on Fatigue Performance

通过车削和旋转弯曲疲劳实验,研究直接时效态GH4169高温合金车削进给量对表面完整性的影响,以及表面完整性对疲劳寿命的影响。结果表明:当进给量f从0.2 mm/r减小到0.02 mm/r时,表面粗糙度R_a从1.497μm减小到0.431μm;表面残余应力从拉应力状态逐渐转变为压应力状态;表面塑性变形层从8μm减小到2μm左右;表面应力集中系数是GH4169疲劳寿命的主要影响因素,随着表面应力集中系数增大,疲劳寿命显著下降;在实验参数范围内,当f=0.13 mm/r时,可获得好的表面完整性,表面应力集中系数K_(st)为1.166,表面显微硬度为405.27HV_(0.025),表面残余应力为82.08 MPa,获得的平均疲劳寿命为6.98×10~4周次;车削表面疲劳断口具有多源疲劳断裂特征,疲劳源起始于试件加工表面的缺陷处。

Through turning and rotary bending fatigue test,the effect of turning feed on GH4169 superalloy surface integrity,and the effect of surface integrity on fatigue life were studied.The results show that the surface roughness Radecreases from 1.497 μm to 0.431μm when the turning feed decreases from 0.2 mm/r to 0.02 mm/r.The surface residual stresses are changed from tensile stress to compressive stress.The depth of plastic deformation layer decreases from 8 μm to 2 μm.The surface stress concentration factor has the most significant effect on the fatigue life of GH4169.With the increase of stress concentration factor,the fatigue life decreases significantly.When f is 0.13 mm/r,the surface stress concentration factor K_(st) is 1.166; the surface micro-hardness is 405.27 HV_(0.025); the surface residual stress is 82.08 MPa; and the average fatigue life is 6.98 × 10~4 cycles.The multiple cracks are initiated at the machined surface defects of GH4169 superalloy specimen.