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针对4Cr9Si2钢排气阀锁夹槽的异常断裂问题,应用热场发射扫描电镜和能谱分析等方法分析了断裂部位的成分、微观组织和形貌。重点分析了钢中富硅区的微观组织,并与粉末包埋热扩散法获得的渗硅层的微观组织进行了对比。结果表明,4Cr9Si2钢排气阀锁夹槽处断裂属严重脆性断裂,源于钢中硅元素的局部严重偏聚引起的组织不均匀,以及富硅区的固有脆性和调幅组织引起的性能不均匀。
In view of the abnormal fracture of the locking groove of 4Cr9Si2 steel exhaust valve, the composition, microstructure and morphology of the fracture site were analyzed by using the methods of thermal field emission scanning electron microscope and energy spectrum analysis. The microstructure of silicon-rich region in steel was analyzed emphatically, and compared with the microstructure of siliconized layer obtained by powder-entrapped thermal diffusion method. The results show that the fracture of the 4Cr9Si2 steel exhaust valve lock slot is a serious brittle fracture, which is caused by the local serious segregation of silicon in the steel, and the inherent brittleness caused by the silicon-rich region and the uneven performance caused by the amplitude modulation structure .