【摘要】 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。更多还原

【Abstract】 In view of the abnormal rupture of a exhaust valve made of 4Cr9Si2 steel upon roll-strengthening,the composition,microstructure and morphology of the fracture part were analyzed with the thermal field emission SEM and EDS method,especially on the microstructure of silicon-rich region of the steel,and a comparison study on microstructure was implemented with the siliconized layer obtained by pack cementation.The experiment results indicate that,the rupture of the part was a kind of embrittlement,trans-granular and inter-granular fracture,originated from the non-homogeneity of microstructure due to serious segregation of silicon element in the steel,as well as the inherent brittleness of silicon-rich phase and the non-uniformity of mechanical properties between the matrix and the spinodal decomposition in the silicon-rich region of the steel.更多还原