MoSi_2发热元件在不同气氛中使用损毁分析

Failure analysis of MoSi_2 heating elements in different atmospheres

对分别在空气气氛中使用100炉和在氮气气氛中使用5炉后(每炉均设定为1 500℃保温3 h)的国产MoSi2发热元件进行了XRD、SEM和EDS分析,并探讨了其损毁机制。结果表明:1)国产MoSi2发热元件未变层气孔较多,腐蚀性气体易通过气孔与MoSi2反应造成损毁,少量的杂质相也可加速损毁;2)MoSi2发热元件在空气气氛中损毁的原因在于SiO2玻璃相以SiO气体挥发致使电阻不均,局部过热;3)氮气气氛中不能形成保护性玻璃膜,N2和少量CO与MoSi2反应生成Mo5Si3、Mo3Si、Mo、Mo2C和Si3N4,使其变质损毁。

Home-made MoSi2 heating elements were used at 1 500 ℃ for 3 h in air for 100 heats and N2 at-mosphere for 5 heats,respectively.They were analyzed by XRD,SEM and EDS,and their failure mecha-nisms were discussed.The results show that：（1 ）there are many pores in the original part,which provide channels for the corrosive gas leading to failure,and a little impurities in the heating elements promote the failure as well;（2）failure of MoSi2 heating elements in air is attributed to SiO gas volatilization from SiO2 glass phase on the surface leading to uneven resistance and local overheat;（3）a protective film cannot form in N2 atmosphere because N2 and a few CO react with MoSi2 forming Mo5 Si3 ,Mo3 Si,Mo,Mo2 C and Si3 N4 leading to the deterioration damage.