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High-Temperature Corrosion Behavior of Commercial Ti-Based Alloys
|Authors: ||Tzung-Sheng Chiou|
|Contributors: ||NTOU:Institute of Materials Engineering|
Ti-based alloys;oxidation behavior;parabolic law;linear rate law;water vapor;sulfidation
|Issue Date: ||2011-06-30T07:23:10Z
|Abstract: ||摘要 本研究主要探討三種商用鈦合金Ti-6Al-4V (Ti-6-4)、Ti-4.5Al-3V-2Mo-2Fe (SP-700)及Ti-6Al-6V-2Sn (Ti-6-6-2)在700-1000℃氧分壓0.01~1atm下的高溫氧化行為。整體而言，三種合金的氧化動力學皆遵守抛物線律，且氧化速率隨溫度上升而加快，除了SP-700及Ti-6-6-2在部分氧分壓下之氧化動力學呈現直線型外。三種合金的氧化生成物主要是由TiO2及少量的Al2O3所組成；而愈往內層，Al2O3的含量愈少。 在探討水氣效應對鈦合金抗氧化性的影響中發現，在通水氣氣氛下，三種合金的氧化生成物亦為TiO2及少量的Al2O3，但通水氣條件下生成的氧化層較為鬆散，特別在氧化層近基材界面處最明顯並伴隨著裂縫產生，而且通水氣合金的氧化速率較未通水氣時快。 在硫氧化研究中，我們僅針對Ti-6-4及SP-700在700-1000℃之H2/H2S/Ar/H2O混合氣氛下進行高溫腐蝕測試，研究結果顯示，兩種合金的硫氧化動力學亦遵守抛物線律，且腐蝕速率隨溫度上升而加快，其腐蝕生成物主要為TiO2及少量的Ti1.19S2和Al2O3；整體而言，合金的硫氧化速率皆比氧化速率快。 關鍵字：鈦合金、氧化行為、拋物線律、直線型律、水氣效應、硫氧化、TiO2、Al2O3、Ti1.19S2|
Abstract The oxidation behavior of Ti-6-4, SP-700 and Ti-6-6-2 was studied over the temperature range of 700-1000℃ in different oxygen containing atmospheres (at Po2=0.01~1atm). The oxidation kinetics of the three alloys followed the parabolic rate law in most cases except for SP-700 and Ti-6-6-2 oxidized linearly at some oxygen partial pressures. The oxidation rate constants of the alloys gradually increased with temperature. The scales formed on the alloys consisted mostly of TiO2 and minor Al2O3 for the three alloys, and the amounts of Al2O3 gradually decreased from the surface to the inner portion of the scales. In addition, the effect of water vapor (water vapor pressure=0.6025%) on the oxidation of the three alloys was also studied. It was found that kp values of the three alloys oxidized in wet air containing water vapor at 0℃ are much faster than those in dry air. The porous scales formed on the alloys also consisted mostly of TiO2 and minor Al2O3 for the three alloys, however the thickness of scales is much thicker in wet air, which corresponded to the fast oxidation rates, as compared to those in dry air. The sulfidation of Ti-6-4 and SP-700 were further studied in H2/H2S/Ar/H2O gas mixture over the temperature range of 700-1000℃. The results indicated that the corrosion kinetics followed the parabolic rate law at all temperatures, and the corrosion rates of both alloys are faster than their oxidation rates. The scales formed on the two alloys in H2/H2S/Ar/H2O gas mixture consisted mostly of TiO2 and minor amounts of Ti1.19S2 and Al2O3. Keywords: Ti-based alloys, oxidation behavior, parabolic law, linear rate law, water vapor, sulfidation, TiO2, Al2O3, Ti1.19S2.
|Appears in Collections:||[材料工程研究所] 博碩士論文|
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