【摘要】 利用简支旋转弯曲疲劳试验机、扫描电镜、显微硬度计及X射线应力分析仪对高合金渗碳轴承齿轮钢的旋转弯曲疲劳裂纹的萌生及扩展行为进行了研究。结果表明：试验钢的疲劳极限强度为973 MPa;疲劳断口由起裂源区、GBF区、鱼眼区、慢速扩展区以及快速扩展区和瞬断区组成。疲劳裂纹萌生起裂源于单一碳化物、聚集团簇碳化物和非金属夹杂物。起裂源的应力强度因子在1.98～3.73 MPa·m^1/2,应力强度因子相当时，夹杂物、聚集团簇及单一碳化物起裂扩展依次需要更长的循环次数。GBF区的应力强度因子集中分布在5.0 MPa·m^1/2左右。聚集团簇碳化物起裂有两种类型：一种是聚集团簇碳化物中存在应力强度因子较大的不规则碳化物，不规则碳化物尖端部分在位错作用下引起应力集中导致裂纹萌生；另一种聚集团簇碳化物由应力强度因子范围在1.90～1.97 MPa·m^1/2的小团块碳化物所组成，团块碳化物与循环应力相互作用导致位错增殖产生较大的应力集中，使得局部临界剪切应变率增加进而引起疲劳裂纹萌生。试验钢的旋转弯曲疲劳寿命与裂纹起裂源夹杂物和碳化物的形状、大小、聚集团簇及受力程度密切相关。更多还原

【Abstract】 Initiation and propagation behavior of rotational bending fatigue cracks in a high alloy carburized bearing gear steel were investigated by using simple supported rotational bending fatigue testing machine, scanning electron microscope, microhardness tester, and X-ray stress analyzer. The results show that the fatigue limit strength of the tested steel is 973 MPa. The fatigue fracture consists of crack initiation zone, GBF zone, fish-eye zone, slow propagation zone, rapid propagation zone, and transient fracture zone. The initiation of fatigue cracks is caused by single carbides, clustered carbides, and non-metallic inclusions. The stress intensity factor of the crack initiation source is in the range of 1.98-3.73 MPa·m^1/2. At the same stress intensity factor, the inclusions, clustered carbides, and single carbide sequentially require longer cycles for crack initiation and propagation. The stress intensity factor of the GBF zone is concentrated around 5.0 MPa·m^1/2. There are two types of crack initiation in the clustered carbides. One is the presence of irregular carbides with high stress intensity factors in the clustered carbides, where the tip of the irregular carbides causes stress concentration under the action of dislocations, leading to crack initiation. Another type of clustered carbide is composed of small agglomerates with stress intensity factors ranging from 1.90 to 1.97 MPa·m^1/2, where the interaction between agglomerates and cyclic stress leads to dislocation multiplication and significant stress concentration, resulting in an increase in the local critical shear strain rate and the initiation of fatigue cracks. The rotational bending fatigue life of the tested steel is closely related to the shape, size, clustering, and stress level of inclusions and carbides as the crack initiation source.更多还原