鈦鋁介金屬合金的高溫氧化與熱腐蝕

High Temperature Oxidation and Hot Corrosion Behavior of Titanium Aluminide Intermetallic Alloys

鈦鋁介金屬合金具有優良的高溫強度，但抗高溫氧化性質不佳限制了此材料在高溫上的應用。在本文中主要探討鈦鋁介金屬合金（Ti3Al-Nb）的高溫氧化和熱腐蝕行為。實驗結果顯示，鋁和鈮含量的增加有助於抗氧化性質的提升，微量的矽和鉻對抗氧化性也有幫助，同時添加釩和鉬及微量的釔（900℃時除外）對抗氧化性則有害。鈦鋁介金屬合金的氧化機構為擴散控制。鈮對抗氧化性的提升在於促進Al2O3的生成和使氧化層更為緻密。Ti56Al25Nb10合金氧化層結構由外而內為Al2O3和TiO2混合層、摻雜少量氧化鈮的TiO2層、TiN層和TiAl層，其中TiN層對氧化層的生長甚有影響。在熱腐蝕行為中，鈉會破壞Al2O3的保護性，硫則會加速氧化反應的進行，不過其行為仍需進一步的研究。

Titanium aluminide alloy has excellent high temperature strength. But its poor oxidation resistance restricts the application of this alloy at high temperature. In this article, high temperature oxidation and hot corrosion behavior of titanium aluminide (Ti3Al-Nb) was investigated and discussed. The experimental results reveal that increasing the content of Al and Nb in the alloy can improve the oxidation resistance. The oxidation resistance can also be slightly increased by small addition of Si or Cr. It is harmful to the oxidation resistance of the alloy by the addition of both V and Mo or Y (except at 900℃). The oxidation mechanism of Ti3Al-Nb alloy is diffusion-controlled. The effect on improving oxidation resistance by the addition of Nb is due to the fact that Nb can promote the growth of Al2O3 and make oxide layer more dense. The structure of oxide layer of Ti65Al25Nb10 alloy from the outer surface to the substrate are Al2O3 +TiO2, TiO2 doped with small amount of niobium oxide, TiN and TiAl. TiN layer plays an important role on the growth of oxide layer. In the hot corrosion behavior, Na can destroy the protective feature of Al2O3 in the oxide layer and S may accelerate the oxidation reaction. Further research on the detailed oxidation and corrosion mechanism at high temperature is needed in the future.