鈦鋁介金屬合金的高溫腐蝕

Hot Corrosion of Ti3Al-Nb Titanium Aluminide Intermetallic Alloy

鈦鋁介金屬合金為極具潛力的高溫材料，因而此合金的高溫腐蝕行為研究實屬必要。研究方法是在試片上噴上硫酸鈉，置於高溫大氣下測其腐蝕速率。實驗結果顯示Ti3Al-Nb合金的硫酸鈉熱腐蝕行為，係遵循抛物線法則，為擴散控制的機構，且腐蝕速率隨著溫度的上升而快速增加。而合金中鈮的添加，有助於改善其抗熱腐蝕性，但添加量太多（超過5at%）則無助益。當噴鹽量在0.3 ~ 1.4mg/cm2的範圍內，改變其濃度大小，對Ti65Al25Nb10。合金腐蝕的影響差異不大。而對抗氧化極有幫助的鋁化鍍層，在抗腐蝕性方面，則顯得不夠理想。

Na2SO4-induced hot corrosion of Ti3Al-Nb alloys follows the parabolic law, which indicates the controlled mechanism is the diffusion of atoms at the surface layer. The corrosion rate increases as the temperature raises in the range of 700 ~ 900℃. The addition of niobium in Ti3Al-Nb alloys can reduce the rate of hot corrosion, but too much addition has little effect. There is no significant changes of the rates of hot corrosion for Ti65Al25Nb10 alloy when the coating amounts of NaSO4 salt varying from 0.3mg/cm2 to 1.4mg/cm2. It is a surprise to find that aluminized Ti65Al25Nb10 alloy has higher rate of hot corrosion than that of unaluminized alloy.