某发动机气门发生断裂失效, 通过对失效气门杆端面和与其接触的摇臂进行宏观分析、扫描电镜分析、能谱分析、金相检验及硬度测试, 找出了发动机气门失效的原因。结果表明: 由于摇臂油孔存在制造偏差, 导致气门杆端面与摇臂摩擦副之间润滑不良, 从而造成该摩擦副之间发生了严重的磨粒磨损, 使得气门杆端面与摇臂之间的间隙增大, 过大的气门间隙又会导致气门锥面的落座力增大, 造成气门颈部应力集中, 并且萌生裂纹, 裂纹不断扩展, 最终造成气门断裂失效。

Some engine valve fractured and the failure reason was analyzed by macro observation, scanning electron microscope analysis, energy spectrum analysis, metallographic examination and hardness test to the valve and rocker arm contacted with the valve. The results show that the manufacture deviation existing in oilhole of the rocker arm resulted in the bad lubrication between the friction pairs of valve and the rocker arm, and made them produced serious abrasive wear. Wear increased the gap between the friction pairs gradually, and then increased the seated force, which induced the stress concentration at the valve neck and production of cracks. The cracks gradually extended and finally resulted in the fracture of the valve.