本研究使用Ti64合金經熱浸鋁、熔射鋁，以及熱浸鋁/熔射鋁後電漿電解氧化處理，於550 oC ~ 750 oC進行靜置恆溫氧化、熱循環氧化及水汽恆溫氧化，探討鈦合金經鋁化處理後，於高溫氧化之作用。並於3.5 wt.% 鹽水環境中進行極化曲線試驗，測試鈦合金經鋁化處理後之常溫抗蝕性。
實驗結果顯示，Ti64合金經熱浸鋁、熔射鋁之鋁化處理後，皆可大幅提升鈦合金之高溫壽命。於650 oC及750 oC熱循環氧化後，Ti64原材之氧化皮膜皆已剝離，熱浸鋁與熔射鋁處理後之試片，於高溫生成鈦鋁介金屬化合物，於此鋁化層內之裂紋尺度雖然會隨著循環次數增加而加深，但經10次熱循環後，其鋁化層仍附著於底材上。在水汽恆溫氧化後，原材及熱浸鋁/熔射鋁後試片皆使皮膜結構變為鬆散，進而加速氧化。熱浸鋁/熔射鋁後再電漿電解氧化試片，於650 oC及750 oC進行恆溫氧化24小時並爐冷至室溫後，氧化陶瓷層皆已失效。鈦合金經熱浸鋁與熔射鋁處理後，皆可提升於750 oC之抗熱循環氧化及抗水汽恆溫氧化，但會使鈦合金之常溫抗蝕性變差，熱浸鋁與熔射鋁後再電漿電解氧化處理，可部分提升鋁塗層之常溫抗蝕性，但無法提升抗高溫氧化性。

In this work, we explore effect of Ti-6Al-4V alloy, aluminized Ti-6Al-4V alloy and oxide layer grown on the aluminized Ti-6Al-4V alloy during the oxidation test. The aluminized Ti-6Al-4V alloy is carried out by hot-dip aluminizing and thermal spraying aluminizing. The plasma electrolytic oxidation technique is employed to fabricate the oxide layer on the aluminized Ti-6Al-4V alloy. In addition, we investigate the effect of thermal oxidation on the aluminized Ti-6Al-4V alloy. The three methods of thermal oxidation test including static oxidation, thermal cycle test and thermal oxidation by steam are used in this experiment. The corrosion resistance of the aluminized specimens are evaluated by the potentiodynamic polarization test in 3.5 wt. % NaCl solution.
According to result of experiment, the delamination at the TiO2/Ti-6Al-4V interlayer are found on the thermal oxidation from 650 to 750 oC. However, the aluminized Ti-6Al-4V alloy after oxidation test are bonded to the substrate due to the growth of Ti-Al intermetallic. We find the scale of the crack increases when increasing the cycle time at the thermal cycle oxidation test. The several voids and cracks at the thermal oxidation by steam are found on the Ti alloy and aluminized specimens to accelerate the rate of oxidation. The PEO coatings on the aluminized Ti alloy under isothermal oxidation test at 650 and 750 oC during 24 hrs. and the PEO coatings are cooled to room temperature. We find the PEO coatings are already delaminated on the substrate. Eventually, hot-dip aluminizing and thermal spraying aluminizing treatment on the Ti alloy increase the oxidation resistance at high temperature while decreasing the corrosion resistance at room temperature.

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