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利用真空非自耗电弧炉制备不同Al含量的Nb-25Ti-8C合金,研究Nb-Ti-Al-C合金的组织结构及其高温氧化行为。研究表明,Nb-25Ti-8C-(0,5,10)Al合金由Nbss和(Nb,Ti)C两相构成;Nb-25Ti-8C-15Al合金由Nbss、(Nb,Ti)C和Nb3Al三相构成。800~1000℃氧化过程中,合金氧化膜为由Nb2O5,Ti O2,Al2O3,Nb O2及Ti Nb2O7多种氧化物构成的混合氧化膜。Ti、Al活性元素可优先与氧发生选择性氧化,抑制氧化物Nb2O5生成,提高氧化膜致密度和合金抗氧化性,并且氧化温度越高,Al元素改善铌合金抗氧化性能效果越明显。Nb-25Ti-8C合金800℃氧化时表现出良好的抗氧化性能,1000℃氧化时Nb-25Ti-8C-x Al合金的抗氧化性能明显优于C-103。随氧化温度升高,氧化膜中Nb2O5含量增加,导致氧化膜与合金基体的内应力增大,引起外层氧化膜脱落。碳化物中C元素以CO2形式挥发导致氧化层表面形成氧化空洞。
The Nb-25Ti-8C alloys with different Al contents were prepared by vacuum non-consumable electric arc furnace. The microstructure and high-temperature oxidation behavior of Nb-Ti-Al-C alloy were studied. The results show that Nb-25Ti-8C- (0,5,10) Al alloy is composed of Nbss and (Nb, Ti) C two phases and Nb-25Ti-8C-15Al alloy consists of Nbss, (Nb, Ti) C and Nb3Al Three-phase composition. In the oxidation process from 800 ℃ to 1000 ℃, the oxide film of the alloy is a mixed oxide film composed of a plurality of oxides of Nb2O5, Ti O2, Al2O3, Nb O2 and Ti Nb2O7. The active elements Ti and Al preferentially oxidize with oxygen, inhibit the formation of oxide Nb2O5, improve the density of oxide film and the oxidation resistance of the alloy, and the higher the oxidation temperature, the more obvious the effect of Al element is to improve the oxidation resistance of the niobium alloy. The oxidation resistance of Nb-25Ti-8C alloy at 800 ℃ is better than that of C-103 at 1000 ℃. With the increase of the oxidation temperature, the content of Nb2O5 in the oxide film increases, leading to the increase of the internal stress of the oxide film and the alloy matrix, causing the oxide film of the outer layer to fall off. Carbide C element in the form of CO2 volatilization led to the formation of oxide layer oxide voids on the surface.