ISSN   1004-0595

CN  62-1224/O4

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喷丸对渗碳高强轴承钢滚动接触疲劳行为影响研究

Effect of Shot Peening on the Rolling Contact Fatigue Behavior of Carburized High-Strength Bearing Steel

  • 摘要: 对经过渗碳处理的高强轴承钢进行不同强度的喷丸处理,研究了渗碳及渗碳+不同强度喷丸复合处理轴承钢的显微组织、硬度梯度、残余应力、表面粗糙度及滚动接触疲劳行为. 结果表明:轴承钢经过渗碳处理后,表层主要由高碳马氏体和蠕虫状碳化物组成,蠕虫状碳化物主要是M23C6、M6C和M7C3型碳化物;渗碳轴承钢经过喷丸处理后其表层发生了塑性变形,导致表层基体(BCC相)的几何必要位错(Geometric necessary dislocation, GND)密度增加;在位错强化的作用下,轴承钢表层的显微硬度略微提高;与渗碳轴承钢相比,渗碳+喷丸轴承钢的表层残余压应力显著提升,而渗碳+喷丸轴承钢的表层残余压应力随着喷丸强度的增加有所下降. 渗碳轴承钢经过不同强度喷丸处理后其滚动接触疲劳中值寿命(L50)随喷丸强度的增加逐次递减,均低于未喷丸处理渗碳轴承钢的滚动接触疲劳中值寿命(L50),这主要归因于渗碳轴承钢经过喷丸处理后,表层粗糙度显著提升,表层凸起或凹陷的数量显著增多,表层均出现了不同尺寸的微裂纹,导致表层应力集中的位置增多,使滚动接触疲劳裂纹萌生机制发生转变,表面疲劳裂纹优先于亚表面疲劳裂纹萌生,表面萌生的滚动接触疲劳裂纹占据主导后,裂纹会以更快的扩展速率和更短的扩展路径发生扩展,导致渗碳+喷丸轴承钢滚动接触疲劳裂纹萌生寿命降低.

     

    Abstract: In this study, the high-strength bearing steel after carburizing treatment was shot peened with different strengths. The microstructure, hardness gradient, residual stress, surface roughness and rolling contact fatigue behavior of carburized and carburized + shot peening composite bearing steels of different strength were studied. The results showed that after carburizing treatment, the surface layer of the bearing steel was mainly composed of high-carbon martensitic and worm-like carbides, and the worm-like carbides were mainly M23C6, M6C, M7C3 carbides, the surface layer of carburized bearing steel undergoes plastic deformation after shot peening, resulting in the increase of the density of geometric necessary dislocation (GND) in the surface matrix (BCC phase). Under the effect of and dislocation strengthening, the microhardness of the surface layer of the bearing steel was slightly increased. Compared with carburized bearing steel, the surface residual compressive stress of carburized + shot peening bearing steel was significantly increased, while the surface residual stress of carburized + shot peening bearing steel decreased with the increase of shot peening strength. The median life of rolling contact fatigue (L50) of carburized bearing steel after shot peening treatment with different strengths decreased with the increased of shot peening strength, which was lower than that of carburized bearing steel without shot peening treatment (L50), which was mainly attributed to the significant increase in surface roughness, the number of surface convex or depressions in the surface layer after shot peening, and the appearance of microcracks of different sizes on the surface, resulted in an increase in the position of surface stress concentration, and the transformation of the initiation mechanism of rolling contact fatigue cracks. Surface fatigue cracks were preferential to subsurface fatigue crack initiation, and after the surface eruption of rolling contact fatigue cracks dominates, the crack would propagate with a faster propagation rate and a shorter propagation path, resulting in a reduction in the initiation life of rolling contact fatigue crack of carburized + shot peening bearing steel.

     

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