鋁化改質效應對MoSi_2基合金抗高溫氧化之研究

Effects of Aluminizing Treatments on Hightemperature Oxidation of MoSi2-based Alloys

本研究探討Mo-Si基三元合金經熔煉(MoSi2)90Al10 (MSA10)及其在經固體滲鋁改質之試片（MS-A），於700 ~ 1100℃之空氣下的氧化行為。研究結果顯示，MSA10合金在700 ~ 800℃呈現加速氧化現象，但在900℃以上具有良好的抗氧化性質；另一方面，MS-A合金在800℃之氧化動力學是加速反應，而900℃則遵守拋物線律，且氧化速率隨溫度增加而趨緩，但在1000℃以上則呈現嚴重的氧化失重現象。由顯微結構分析得知，MSA10在800℃氧化所形成的Al2O3氧化層較為鬆散，保護性較差；在900℃以上氧化後，其表面會形成較緻密的α-Al2O3保護層，能有效地提升MoSi2的抗氧化能力；而MS-A，經氧化後亦會生成具保護層的α-Al2O3，但會有較多且不連續裂縫，其保護效果較差。

The effects of adding 10 at.% Al to form (MoSi2)90Al10 and surface aluminizing (MS-A) on the isothermal oxidation of MoSi2-based alloys were investigated over the temperature range of 700 ~ 1100 ℃ in dry air. The breakaway kinetics of the MSA10 alloy was observed at T ≤ 800 ℃, however, the parabolic kinetics with better oxidation resistance was noted at T ≥ 900 ℃. On the other hand, the mass-loss kinetics was observed at T ≥ 1000 ℃ for the MS-A alloy. The Al2O3 layer formed on the MSA10 at 800 ℃ that provided poor oxidation resistance. However, the scales formed on MSA10 was composed of α-Al2O3 at T ≥ 900 ℃, whose formation is responsible for the better oxidation resistance. On contrast, the α-Al2O3 layer formed on the MS-A alloy containing numerous crackes, which provided poor oxidation resistance.