镀铬对8Cr4Mo4V钢疲劳行为的影响

摘要

某型发动机轴承在航空发动机装配过程中处于盲装状态,其故障发生率较高.为了控制轴承在工作状态下的游隙需要对轴承进行镀铬,然而镀铬对轴承疲劳寿命及航空发动机的性能有很大影响.为了确保轴承的使用寿命,保证发动机安全可靠工作,研究了镀铬对航空发动机轴承用材料8Cr4Mo4V钢疲劳行为的影响.结果表明:镀铬试样的疲劳强度由镀铬前的860 MPa降到540 MPa,缺口试样镀铬后的疲劳强度由镀铬前的310 MPa降到95 MPa,通过扫描电镜观察发现,镀层中的微裂纹是引发速断的疲劳源.%The bearing is assembled in an aeroengine under unviewable condition, which probably leads to high malfunction rate. Chroming was used in bearing to control its clearance under working circumstances. However, Chroming plays an important influence of fatigue life and overall performance. The influence of chroming on the fatigue behaviors of 8Cr4Mo4V steel which widely used in aero-engine bearing was researched in order to ensure the working life of bearing and the reliable operation of engine. The results show that the fatigue strength r-1 ( 107 times) of sample decreased from 860 MPa to 540 MPa by chroming, while the fatigue strength of gaped sample decreased from 310 MPa to 95 MPa by chroming. The SEM observation shows that the microcracks in the chrome coating are the main reasons of the fracture initiation.