对3个典型的发动机气门弹簧断裂件进行了理化检验和扫描电镜断口分析。结果表明: 3个气门弹簧的失效机理均为疲劳断裂,而引起疲劳断裂的原因均与气门弹簧的表面质量有关; 1号气门弹簧的断裂原因是表面存在非金属夹杂物, 2号气门弹簧的断裂原因是表面存在锈蚀坑, 3号气门弹簧的断裂原因是表面存在折叠缺陷。因此, 控制原材料质量和避免表面缺陷是提高气门弹簧服役寿命的关键举措。

The physical and chemical testing and SEM analysis of the fracture were carried out on three typically fractured valve springs of motors. It was concluded that all the fracture mechanisms of the three valve springs were the fatigue fracture. The reasons causing the fracture were related to surface quality of valve springs. The fracture reason of No.1 valve spring was that non-metallic inclusions exsited in the surface. The fracture reason of No.2 valve spring was that corrosion pits exsited in the surface. The fracture reason of No.3 valve spring was that the folding defect exsited in the surface. Therefore, the key measures to improve the service life of valve springs were to control the quality of raw materials and avoid the surface defects of the valve springs.