β相凝固铸造高Nb-TiAl合金的高温氧化行为

High temperature oxidation behavior of high niobium containing TiAl alloys obtained by β phase solidification

研究了β相凝固的铸造合金Ti45Al8Nb0.2W0.25Cr和Ti45Al8Nb0.2W0.25Cr0.2B0.02Y合金900℃×130 h的循环抗氧化性能,探讨了B、Y元素对合金抗氧化性能的影响。结果表明,0.2B0.02Y的添加能在一定程度上改善合金的抗氧化性能。B、Y的加入能够促进合金表层形成致密连续的Al2O3层,抑制氧元素的进一步入侵,Y的加入使得合金氧化层的抗剥落性能得到提高。分析计算得出了两种合金的氧化动力学曲线,氧化10 h后,Ti45Al8Nb0.2W0.25Cr合金的氧化动力学方程中的幂指数n=1.87,合金单位面积的氧化增重随氧化时间的变化规律介于直线规律和抛物线规律之间,即这种合金的氧化膜保护性不足。Ti45Al8Nb0.2W0.25Cr0.2B0.02Y合金氧化动力学方程中的幂指数n=2,合金单位面积的氧化增重随氧化时间的变化规律为抛物线规律,利于合金表面生成保护性的氧化膜,合金的抗氧化性较好。

The cyclic oxidation resistance of β phase solidification cast Ti45Al8Nb0.2W0.25Cr and Ti45Al8Nb0.2W0.25Cr0.2B0.02 Y alloys oxidized at 900 ℃ for 130 h was studied,and effects of B,Y elements on oxidation resistance of the alloy were studied.The results indicate that the addition of 0.2B0.02 Y can improve the oxidation resistance of the alloy.The element B and Y can promote the formation of a dense continuous Al_2O_3 layer on the alloy surface which can restrain the invasion of oxygen,the addition of Y can improve the alloy oxide layer peeling resistance.Oxidation kinetics curves of the two kinds of the alloy were concluded by analysis calculation,the power exponent of Ti45Al8Nb0.2W0.25 Cr alloy oxidation kinetics equation is 1.87 after oxidation for 10 h,the changing rule of the alloy oxidation mass per unit area with the changing rule of the oxidation time is between linear and parabolic rule,which suggests that the alloy oxide film is lack of enough protection.While the power exponent of Ti45Al8Nb0.2W0.25Cr0.2B0.02 Y alloy oxidation kinetics equation is 2,the changing rule of the alloy oxidation mass per unit area along with the oxidation time meets the parabolic law,it can benefit to generate the protective oxide film on the alloy surface,and it shows a better oxidation resistance.