超高压烧结制备cBN/Sialon复合材料及烧结过程中的失效分析

Improvement of heating system and preparation of cBN/Sialon composites using HPHT method

在使用六面顶压机合成cBN/Sialon复合材料的实验过程中,当石墨杯内径为18.8mm时,烧结过程一切正常。当石墨杯内径扩展为22.0mm后,电流突降、电阻突升的情况开始出现。阐述了电阻突升可能造成的危害,从加热系统的各部分结构与组装方式入手,分析了电阻突升的原因,结果表明,烧结过程中发生较大体积收缩的Si3N4导致了加热电流回路的崩溃。改进组装方式后顺利合成了具有良好机械性能的cBN/Sialon复合材料,随着保温时间的增加,Sialon的Z值增加,发育良好的棒状β-Sialon晶体均匀分布于烧结体中。

Using the cubic hinge press to fabricate the cBN/Sialon composites,the sintering process was fine when graphite inner diameter was 18.8 mm.After increasing the graphite inner diameter to 22.0 mm,the electric current decreased and the electric resistance increased dramatically.In the paper,the harmfulness of the electric phenomenon mentioned above was discussed.By analyzing the structure of the heating system,the reason of the abnormal electric phenomenon was revealed.The results showed that the heating system collapsed when the large shrinkage of Si_3N_4 occurred during sintering.The cBN/Sialon composites were successfully prepared after the assembly structure was updated.Z value of β-Sialon increased with holding time increasing,and the rod-like grains of β-Sialon was uniformly distributed in the compacts.