对发生断裂的某应急柴油发电机缸套与活塞进行了宏微观形貌观察、金相检验、化学成分分析、能谱分析及硬度等测试, 并对曲轴箱润滑油的含水量进行了检测, 系统分析了柴油发电机缸套和活塞失效的原因。结果表明: 活塞所用材料为未经变质处理的共晶铝硅合金, 存在粗大片状初晶硅和长针状的共晶硅, 易割裂基体, 从而降低了材料的塑性及耐磨性; 缸套因润滑不足存在拉缸现象, 加速了活塞的断裂解体, 产生的活塞碎片撞击缸套, 从而导致缸套发生局部断裂解体。

By means of macro and micro morphology observations, metallographic analysis, chemical composition analysis, EDS and hardness test for the factures of piston and cylinder liner, as well as water content analysis in oil in crankcase, the failure causes of the piston and cylinder liner for emergency diesel generator were investigated. The results show that without modification treatment, the eutectic aluminium-silicon alloy of the piston which had coarse flake primary silicon and long needle-like eutectic silicon made it easy to break away from the matrix and then lower its plasticity and wearability. Under the combined action of cylinder score due to poor lubrication, the disintegration of the piston was accelerated and the piston fragments impacted onto the cylinder liner, finally caused the local fracture of the case.