CO₂ 레이저 빔에 의한 Si₃N₄ 세라믹의 반응연구

Surface transform of Si₃N₄  ceramics irradiated by CO₂ laser beam

  Silicon Nitride (Si₃N₄), which is widely used in a variety of applications, is hard-to-machine due to its high hardness. At high temperature (e.g. above 1000℃), however, the machinability can be greatly improved. In this work, we used a CO₂ laser with a high absorptivity to Si₃N₄ of 0.9 to locally heat the surface of a rotating Si₃N₄ rod on a lathe. In order to examine the effects of the laser-assisted heating on hardness, an Si₃N₄ rod is heated to temperatures from 900 to 1800℃ and is rotated at speeds from 440-900 rpm in experiments. When the rod is naturally cooled to room temperature, we measured the Vickers hardness (Hv); and observed the surface of HAZ using a scanning electron microscopy (SEM). Energy dispersive spectroscopy(EDS) was used for ingredient analysis. Results showed that when heated at 1600℃, the hardness of Si₃N₄ decreased from 1500 Hv to 1000 Hv. Also, in order to predict the depth of HAZ, we numerically analyzed the laser-assisted heating of Si₃N₄.