反应热压烧结Si_3N_4–ZrSi_2–ZrN–BN陶瓷及其加工性能

Preparation of Si_3N_4–ZrSi_2–ZrN–BN Ceramic by Reactive Hot Pressing and Its Processing Properties

以60%(质量分数)Si_3N_4和30%ZrB_2为主要原料、10%Al_2O_3–Y_2O_3为助剂,通过反应热压烧结制备可电火加工和机械加工的Si_3N_4基陶瓷。结果表明:在1 600℃氩气和真空环境下ZrB_2均可以与Si_3N_4发生完全的化学反应,获得Si_3N_4–ZrSi_2–ZrN–BN陶瓷。由于导电相ZrSi_2和ZrN的形成,Si_3N_4基陶瓷具有较优异的导电性能,适合电火花线切割加工。然而,在氩气和真空环境下反应生成的h-BN具有不同的显微形貌,导致在氩气环境下制备的Si_3N_4–ZrSi_2–ZrN–BN陶瓷具有良好的钻孔可加工性,在真空环境下制备的Si_3N_4–ZrSi_2–ZrN–BN陶瓷具有较差的钻孔可加工性。因此,在氩气下反应热压烧结制备的Si_3N_4–ZrSi_2–ZrN–BN陶瓷具备良好的可电火花加工和机械加工性能。

Si3N4-based ceramic was prepared by reactive hot pressing using 60%Si3N4 and 30%ZrB2 as raw materials and 10%Al2O3-Y2O3 as sintering aids. The electrical discharge and machinable properties were determined. The results show that Si3N4-ZrSi2-ZrN-BN ceramic is obtained via the reaction between ZrB2 and Si3N4 in both argon and vacuum environments at 1 600 ℃. Due to the formation of ZrSi2 and ZrN phases, reactive hot-pressed Si3N4-based ceramic exhibits a good electrical conductivity, which is suitable for wire electrical discharge machining （W-EDM）. However, the h-BN particles formed in argon and vacuum environments have different morphologies, leading to different drilling machinabilities of Si3N4-based ceramic. The Si3N4-ZrSi2-ZrN-BN ceramic hot-pressed in argon has a good machinability, whereas the Si3N4-ZrSi2-ZrN-BN ceramic hot-pressed in vacuum has a poor machinability. As a result, the Si3N4-ZrSiE-ZrN-BN ceramic reactively hot-pressed in argon has both good EDM and machinability.