Cr4Mo4V轴承钢旋转弯曲疲劳寿命及疲劳裂纹萌生机理  

Rotational bending fatigue life and fatigue crack initiation mechanism of Cr4Mo4V bearing steel

作　　者：郭军 杨卯生[2] 卢德宏[3] 李新宇[2,3] GUO Jun;YANG Mao-sheng;LU De-hong;LI Xin-yu(Collaborative Innovation Center of Steel Technology,University of Science and Technology Beijing,Beijing 100083,China;Institute for Special Steel,Central Iron and Steel Research Institute,Beijing 100081,China;Faculty of Material Science and Engineering,Kunming University of Science and Technology,Kunming 650093,China)

机构地区：[1]北京科技大学钢铁共性技术协同创新中心,北京100083 [2]钢铁研究总院特殊钢研究所,北京100081 [3]昆明理工大学材料科学与工程学院,昆明650093

出　　处：《材料工程》2019年第7期134-143,共10页Journal of Materials Engineering

基　　金：国家高技术研究发展计划项目(863计划)(2012AA03A503)

摘　　要：通过室温旋转弯曲疲劳实验研究Cr4Mo4V轴承钢旋转弯曲疲劳寿命和疲劳裂纹萌生机理。在PQ1-6型旋转弯曲疲劳试验机上进行旋转弯曲疲劳实验,通过升降法测得疲劳极限和S-N曲线,使用SEM对疲劳试样断口进行观察,分析起裂源类型和裂纹扩展行为,通过缺陷所在位置的名义应力幅与测得缺陷疲劳极限强度的比值σ′/σw,defect分析了缺陷尺寸对疲劳寿命的影响。结果表明:Cr4Mo4V轴承钢的安全疲劳极限为1019MPa,Cr4Mo4V轴承钢S-N曲线数据呈下降趋势且分散性较大。断口观察表明,Cr4Mo4V轴承钢起裂类型有5种,即近表面碳化物起裂、近表面非金属夹杂物起裂、内部非金属夹杂物起裂和内部碳化物起裂。内部起裂断口有"鱼眼"特征;疲劳寿命超过107周次,内部起裂源碳化物周围形成GBF区。Cr4Mo4V轴承钢中碳化物在循环应力作用下发生破碎,破碎的碳化物加大了裂纹扩展速率。使用关键碳化物体积密度能够定量地分析碳化物尺寸对近表面起裂的影响。σ′/σw,defect都大于1,σ′/σw,defect越大疲劳寿命越短。The rotational bending fatigue life and fatigue crack initiation mechanism of Cr4Mo4V bearing steel were studied by means of rotating bending fatigue test at room temperature.The rotational bending fatigue test was carried out on a PQ1-6 rotary bending fatigue test machine.The fatigue limit and S - N curve were measured by the up-down method.The fracture of the fatigue specimen was observed by SEM,and the crack initiation source type and crack propagation behavior were analyzed.The effect of defect size on fatigue life was analyzed by the ratio σ′/σ w,defect of the nominal stress amplitude at the location of the defect to the measured ultimate fatigue strength of the defect.The results show that the safety fatigue limit of Cr4Mo4V bearing steel is 1019MPa,and the S-N curve data of Cr4Mo4V bearing steel shows a downward trend and a large dispersion.Fracture observation shows that there are five types of initiation,namely surface defects leading to initiation,near-surface carbides leading to initiation,near-surface non-metallic inclusions leading to initiation,internal non-metallic inclusions leading to initiation and internal carbides initiation.Internal crack fractures have fish-eye features.When the fatigue life exceeds 10 7 cycles,a granular bright area (GBF) is observed in the vicinity around the internal initiation source carbides.The fatigue fracture was observed with broken carbides,and the broken carbide increased the crack growth rate.Carbides cracking can occur in the bearing steel Cr4Mo4V under the action of cyclic stresses.These fractured carbides attract the crack tip leading to faster growth rate.Influence of carbide size on the near surface initiation can be quantitatively analyzed by using the critical volume density of carbides.The values of σ′/σ w,defect are higher than 1 and the larger the σ′/σ w,defect,the shorter the fatigue life is.

关 键 词：轴承钢 旋转弯曲疲劳 碳化物 夹杂物 

分 类 号：TG115.57[金属学及工艺—物理冶金]