Nb-Ti-Si-Cr基超高温合金在1250℃下的氧化行为

Oxidation Behavior of Nb-Ti-Si-Cr Based Ultra-high Temperature Alloy at 1250 ℃

采用真空非自耗电弧熔炼法制备了Nb-22Ti-14Si-20Cr-3Al-5Hf-1.5B-0.06Y(at%)超高温合金,在1250℃下分别进行1、5、10、20、50和100 h高温氧化试验。采用XRD、SEM及EDS分析了合金氧化膜及其合金基体的相组成、组织形貌和成分。结果表明:氧化膜分为两层,致密的外层和疏松的中间层,外层组织由Ti0.4Cr0.3Nb0.3O2组成,并含有少量TiNb2O7和SiO2,且随着氧化时间的延长,TiNb2O7含量逐渐减少,Ti0.4Cr0.3Nb0.3O2的含量逐渐增多;氧化膜中间层主要由(Ti,Cr)NbO4、Ti2Nb10O29和Nb2O5组成;氧化后合金基体内Cr2Nb和Nbss元素发生互扩散,界面处出现过渡区。

Nb-22Ti-14Si-20Cr-3A1-5Hf-1.5B-0.06Y （at.%） alloy ingot was prepared by vacuum consumable arc melting. The ingots were oxidized in an open-ended furnace at 1250 C for 1, 5, 10, 20, 50 and 100 h, respectively. X-ray diffraction analysis was used to identify the phase presenting in both oxide scales and alloy substrate. The cross sections of the oxidized specimens were observed by scanning electron microscopy （SEM） and the chemical composition of the constituent phases were analyzed by using energy dispersive spectroscopy （EDS）. The results show that the oxide scale consists of two layers： a compact outer layer and a looser intermediate layer. The constituent phases of the outer layer are Tio.4Cro.3Nbo.302, TiNb207 and SiO2. As the oxidation prolonging, the content of TiNb207 reduces, but the content of Tio.4Cro3Nb0302 increases. The constituent phases of the intermediate layer is （Ti, Cr）NbO4, Ti2NbloO29 and Nb205. There are transitional regions presenting in the phase boundaries between Cr2Nb and Nbss in the substrate just below the oxide scales, which show that the element re-partitioning between the two phases occurs during the oxidation process.