氮化鈦的鋁化反應與氧化行為

Abstract

氮化鈦(Titanium Nitride, TiN)在1atm氬氣(Ar) 保護氣氛下，利用粉末擴散法(pack cementation method)進行850∼1150℃持溫10 hr之鋁化反應，利用X光繞射(x-ray diffraction, XRD) 與掃描式電子顯微鏡(scanning electron microscopy/energy dispersive spectroscopy, SEM/EDS)，分析反應後之顯微結構。TiN在850 ℃/10hr之鋁化反應後，鋁化層內的生成物為TiAl3 (tetragonal)與AlN(hexagonal)。然而，TiN在1150℃/10hr之鋁化反應後，鋁化層內的生成物多了TiN (cubic)。接著將鋁化後之試片暴露在1000℃的空氣中進行長時間(250 hrs)的氧化實驗，經過氧化反應後，發現經850℃/10 hr鋁化處理之試片，其抗氧化性明顯較佳的主要原因是有較多的AlN，氧化時形成連續的Al2O3保護層。相反地, 和經1000 ~1150℃/10 hr鋁化處理之試片相較之下，其抗氧化性都較未經鋁化處理的TiN更差，推測是因為氧化行為受到鋁化層中的AlN與TiAl3之相對比例及分佈情況所影響。TiAl3氧化形成TiO2/ Al2O3混合層並無法提供保護的效果；而少量的AlN氧化時也無法形成連續的Al2O3層。

In this work, the aluminization and oxidation reactions of Titanium Nitride (TiN) were investigated. TiN samples were annealed by using the pack cementation method at temperatures ranging from 850 to 1150℃in argon atmosphere for 10hours. The microstructures of the reaction interface were characterized using x-ray diffraction (XRD) and scanning electron microscopy (SEM). Phases of AlN(hexagonal) and TiAl3(tetragonal) were observed in the aluminized layer after reaction at 850℃ for 10hrs. However, Phase of TiN(cubic) was addationally formed in the aluminized layer after reaction at 1150℃ for 10hrs. After the optimum pack cementation treatment, the coated specimens were oxidized at 1000℃ up to 250 hrs in air. After oxidation, the TiN which was aluminization- treated at 850℃had batter oxidation resistance than the untreated TiN because of more AlN proportions relative to TiAl3 so as to form a continuous and dense Al2O3 protection layer. On the contrary, the TiN which was aluminized at 1000 or 1150℃had poor oxidation resistance than the untreated TiN. On the one hand, this is because TiAl3 would be oxidized to form TiO2/ Al2O3 mixed layers without offering better oxidation resistance. On the other hand, less amount of AlN would not be able to form a continuous Al2O3 protection layer.