高钴钼低碳不锈轴承钢的拉压疲劳裂纹萌生与扩展

Tension and compression fatigue crack initiation and propagation of high cobalt molybdenum low carbon stainless bearing steel

采用QBG-50型高周疲劳试验机对高钴钼不锈轴承钢进行轴向拉压疲劳试验,研究了其在室温和500℃下的疲劳裂纹萌生扩展行为。结果表明:室温条件下试验钢的拉压疲劳极限强度为785 MPa,500℃条件下试验钢的拉压疲劳极限强度为550 MPa,较室温降低了30.0%。通过扫描电镜对疲劳断口观察发现,室温下试验钢的疲劳裂纹起裂类型为单源起裂,起裂源为驻留滑移带、表面加工缺陷和夹杂物,高温下试验钢的起裂类型为单源起裂和多源起裂,起裂源为驻留滑移带、夹杂物和表面加工缺陷。室温下疲劳裂纹萌生于内部驻留滑移带,而500℃下疲劳裂纹多形成在表面或接近表面的滑移带。拉压裂纹萌生寿命占总寿命的97.88%以上。

The axial tension and compression fatigue test of high cobalt molybdenum stainless bearing steel was carried out by QBG-50 high cycle fatigue testing machine,and the fatigue crack initiation and propagation behavior of the steel at room temperature and 500℃was studied.The results show that the ultimate tensile-compression fatigue strength of the experimental steel is 785 MPa at room temperature and 550 MPa at 500℃,which is 30.0%lower than that at room temperature.Through the observation of fatigue fracture surface by scanning electron microscopy,it is found that the fatigue crack initiation type of the experimental steel at room temperature is single source initiation,and the initiation sources are persistent slip bands,surface processing defects and inclusions.The initiation types of the experimental steel at high temperature are single source initiation and multi-source initiation,and the initiation sources are persistent slip band,inclusions and surface processing defects.At room temperature,the fatigue cracks are initiated in the internal persistent slip bands,while at 500℃,fatigue cracks mostly originate from the persistent slip bands on or near the surface.The initiation life of tension and compression crack accounts for more than 97.88%of the total life.