工程陶瓷微爆轰弧加工过程的观察与分析

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An experimental system is established to observe and analyze the micro-detonation arc machining（MDAM） process.By means of high speed photography and current signal acquisition,the relationship between the external shape of micro-detonation arc and the working current is studied.The formations of ablation pit in Si3N4 and Al2O3 are observed by using high speed photography and the surface and cross-section topography are observed by using scanning electron microscape（SEM）.The experimental results show that the diameter of micro-detonation arc increases with the working current and the diameter of ablation pit expands with the machining time;Si3N4 ceramic can decompose in machining,the surface structure is loosen,and some transverse cracks at subsurface are produced by thermal shock;Al2O3 ceramic can directly melt in machining,lots of micro-cracks distribute on the surface,and the main composition of deteriorative layer in grass phase.建立了微爆轰弧加工（MDAM）实验系统,对工程陶瓷MDAM过程进行观察及分析。通过运用高速摄像和电流信号测量技术手段,对微爆轰弧的外观形态及工作电流对其影响进行了分析,对Si3N4和Al2O3两种材料的轰击蚀坑形成过程进行了高速摄像观察,并利用扫描电镜（SEM）观察了轰击蚀坑的表面及截面形貌。结果表明,微爆轰弧的直径随着工作电流的增大而增大,轰击蚀坑直径随着轰击时间的延长而逐渐扩展。Si3N4陶瓷加工时升华分解,蚀坑表面结构疏松,并在亚表面由热冲击造成横向裂纹。Al2O3陶瓷在加工时直接熔化,生成的蚀坑表面密布微裂纹,截面上部的变质层主体成分为玻璃相。