激光磨抛复合强化对15CrMnMoVA钢孔结构疲劳性能的影响研究

Effect of composite strengthen process of laser shock,grinding and polishing on the fatigue properties of 15CrMnMoVA hole structure

对15CrMnMoVA钢试件孔结构采用了坐标磨、数控磨抛和激光磨抛复合强化等不同工艺进行加工,分析其表面完整性特征,并对试件进行对称循环加速疲劳寿命试验。结果表明,试件孔结构的疲劳破坏机制为微动疲劳,增加孔的倒角尺寸会导致疲劳寿命降低;与传统的坐标磨工艺相比,数控磨抛工艺可以提高疲劳极限5%,而激光强化与数控磨抛复合工艺可以提高疲劳极限20%;激光强化能形成较深的残余压应力强化层,数控磨抛后残余压应力层仍然深达0.5 mm;数控磨抛可以提高孔的形状精度至0.009 mm,并进一步将孔壁抛光至镜面(表面粗糙度为Ra 0.018μm);激光磨抛复合强化工艺显著提高了孔结构的疲劳性能。

The 15CrMnMoVA steel specimens with hole structure were processed through different methods including coordinate grinding,laser strengthening and Numerical Control(NC)grinding and polishing.The surface integrity was analyzed,and the accelerated fatigue tests were conducted on the specimens.The results show that the failure mechanism of the hole structure is fretting fatigue.The increase of the chamfer size results in a decrease in fatigue life.Compared with the traditional coordinate grinding,the NC grinding and polishing process increases the fatigue limit of components by 5%,while the composite process of laser shock,NC grinding and polishing increases the fatigue limit by 20%.The laser shock generates a deep strengthening layer with considerable compressive residual stress.After the NC grinding and polishing,the residual compressive stress is still as deep as 0.5 mm.The NC grinding and polishing improves the shape accuracy of the hole to 0.009 mm.The final NC polish decreases the surface roughness to Ra 0.018μm.The composite process significantly improves the fatigue performance of the hole structure components.