8Cr4Mo4V钢激光冲击残余应力的演化仿真及其对疲劳性能的影响

Simulation of Residual Stress Evolution of 8Cr4Mo4V Steel Induced by Laser Shock and Its Influence on Fatigue Performance

对8Cr4Mo4V钢的激光冲击残余应力进行演化仿真和实验验证,并观察其微观组织、检测其硬度和旋转弯曲疲劳性能,研究了激光冲击强化对其残余应力和疲劳性能的影响。结果表明,激光冲击强化在8Cr4Mo4V钢的表层产生了较大的残余压应力,有限元法的计算结果和实测值分别为-607和-584 MPa。在激光冲击强化过程中等离子体冲击波使8Cr4Mo4V钢表面的碳化物碎化和次表面二次碳化物析出,在近表面产生的剧烈塑性变形使表面硬度提高。同时,残余应力、表面硬度的提高以及次表面二次碳化物的析出抑制了疲劳裂纹的萌生,使裂纹的扩展速率降低,裂纹源由表层转移到次表层。激光冲击强化使8Cr4Mo4V钢的旋转弯曲疲劳性能显著提高,疲劳强度提高约45.95%。

The effect of laser shock peening(LSP)on the residual stress and fatigue properties of 8Cr4Mo4V steel was studied by numerical simulation and experimental verification in terms of the residual stress evolution,microstructure observation,hardness and rotating bending fatigue performance tests.The results show that LSP causes a large compressive residual stress on the surface of 8Cr4Mo4V steel,which was acquired to be-607 MPa and-584 MPa by finite element method and the experimental measurement.During the process of LSP,the plasma shock wave may shatter carbides on the surface of the steel into smaller pieces,while induce the secondary precipitation of subsurface carbides and the severe plastic deformation of the substrate near the surface,thus increasing the surface hardness of the 8Cr4Mo4V steel.The increase of residual stress and surface hardness and the precipitation of secondary carbides on the subsurface may effectively inhibit the initiation of fatigue cracks and slow down the crack propagation rate.Therefore,the crack source is transferred from the surface layer to the subsurface layer.The fatigue strength of 8Cr4Mo4V steel after LSP is increased by about 45.95%and the rotating bending fatigue performance is significantly improved.