柴油机排气阀盘面断裂的失效分析

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The failure of the exhaust valve was investigated using the optical microscope, SEM and EDS. The result showed that the fracture of valve was mixture of inter-granular and trans-granular fracture with characteristic of herringbones, river patterns and dimples. Corruption oxidation action happened with the inclusion and oxide during the fracture. Corruption oxidation and the interaction of high frequency impact stress and heat stress resulted in fatigue fracture in the valve.利用金相显微镜、扫描电镜、能谱分析仪等对某柴油机排气阀盘面的断口进行了观察和分析．结果表明：阀盘面的断口出现人字纹、河流花样和韧窝等特征．为沿晶＋穿晶混合型断裂；断口处有夹杂物．断裂面上裂纹尖端覆盖有一层氧化皮．表明断裂过程中有腐蚀氧化过程；腐蚀氧化、高频率冲击和热应力等共同作用导致了阀盘面的疲劳断裂．