高強度鈦合金高溫乾空氣與含水汽之氧化行為研究

Effect of Water Vapor on High-temperature Oxidation of Commercial Titanium-based Alloys

本研究主要在探討水汽氣氛對兩種商用鈦合金（含Ti-6Al-4V，簡稱Ti-6-4及Ti-4.5Al-3V-2Mo-2Fe，簡稱SP-700）在700 ~ 900℃間氧化行為的效應。研究結果顯示，兩種鈦合金在不同氣氛下的氧化動力學皆遵守抛物線型定律，且氧化速率皆隨溫度的上升而加快，同時在含水汽環境下的氧化速率皆較在乾空氣下快。兩種合金氧化後的主要生成TiO2，並有少量Al2O3生成，其中Al2O3愈往內部氧化層的含量愈少；此外，含水汽下的氧化層結構明顯較為鬆散，是氧化速率較乾空氣快的主因。

The effect of water vapor on the high-temperature oxidation behavior of commercial Ti-6Al- 4V (Ti-6-4) and Ti-4.5Al-3V-2Mo-2Fe (SP-700) alloys was studied over the temperature range of 700 ~ 900 ℃ in air. The results showed that the oxidation kinetics of the two alloys followed the parabolic rate law, and the oxidation rate constants (kp values) of the alloys gradually increased with increasing temperature. It was found that kp values of the two alloys (Ti-6-4 and SP-700) oxidized in air containing water vapor were much faster than those in dry air. The scales formed on the alloys consisted mostly of TiO2 and minor Al2O3. The scale thickness of the two alloys in water-vapor containing air is much thicker and more porous, which is responsible for the fast oxidation rates, as compared to that in dry air.