热压烧结对Laves相NbCr2合金组织及高温氧化行为的影响

Effect of hot pressing parameters on microstructure and high temperature oxidation behavior of Laves phase NbCr_2 alloys

研究了不同热压温度和时间对Cr-33at%Nb合金显微组织及氧化行为的影响,并用SEM和X射线衍射对合金组织及氧化产物进行了分析。结果表明,热压温度升高有利于组织致密,保压时间延长有利于Laves相NbCr2热反应合成。不同热压条件制备的Cr-Nb合金在1200℃的氧化动力学均近似符合抛物线规律,氧化膜均由两部分组成,外层为Cr2O3,内层为CrNbO4。随着热压温度的升高,合金氧化速率减小;保压时间由15min延长到80min时,合金氧化速率逐渐减小,但当达到120min时,氧化速率又有所提高。

The influences of sintering temperature and sintering time on microstructure and oxidation behavior of the hot pressed Cr-33at% Nb alloys were investigated by X-ray diffraction, scanning electron microscopy. The resuhs show that the relative density of the hot pressed alloys increases with sintering temperature or sintering time increasing. The effect of sintering temperature on the densification behavior is more significant than that of sintering time. The main influence of sintering time increasing is on the synthesis of Laves phase NbCr2. The oxidation kinetic curves of all specimens are approximately parabola and a multi-layered scale is formed, consisting of an outer layer being a porous, loosely adherent Cr2O3 layer and the inner layer of CrNbO4. The oxidation resistance is found to increase with increasing sintering temperature and sintefing time from 15min to 80min, however, as sintering time prolong to 120min, the oxidation resistance reduces gradually.