Low-Temperature Oxidation Behavior of (Zr1/3Nb1/3Ti1/3)C Solid-Solution Ceramics in Air

Abstract

In order to investigate the low-temperature oxidation behavior of the ternary carbide solid-solution ceramics, the low-temperature oxidation behavior of (Zr1/3Nb1/3Ti1/3)C (ZNTC) solid-solution ceramics was investigated by the isothermal-exposure oxidation test at 1073~1473 K in air for 120 minutes. The results showed that ZNTC samples possessed good low-temperature oxidation resistance and their oxidation process could be described by a parabolic rate law. As oxidation temperature increasing from 1073 to 1473 K, the calculated parabolic rate of ZNTC decreased slowly from 1073 to 1173 K, then increased rapidly from 1173 to 1273 K, and finally decreased gradually from 1273 to 1473 K. This behavior was primarily attributed to the evolution of the composition and microstructure in the oxide layers. Specifically, the oxidation products were mainly composed of ZrO2, Nb2O5, and TiO2 at 1073~1173 K, and then transformed into the composition of ZrTiO4, TiNb2O7, and Nb2Zr6O17 at 1273~1473 K. In addition, in the view of surface and cross-section, the morphology feature of oxidation products changed with the oxidation temperature.

为了研究三元碳化物固溶体材料的低温氧化行为，利用等温暴露氧化实验方法研究了(Zr1/3Nb1/3Ti1/3)C固溶体陶瓷在不同低温空气中的氧化行为。研究结果表明，在1073～1473 K 温度范围内，(Zr1/3Nb1/3Ti1/3)C固溶体陶瓷具有优良的低温抗氧化性能，其氧化动力学符合抛物线规律，氧化过程受氧气在氧化层中的扩散速率控制；随着氧化温度升高，该材料的氧化速率常数表现出先缓慢降低、再迅速增加、最后逐渐降低的趋势。上述结果可主要归因于该陶瓷在不同温度下形成的氧化层的物相组成及微观结构的演变，即该材料在1073～1173 K温度下的氧化产物主要是由简单的ZrO2、Nb2O5和TiO2相组成，而在1273～1473 K温度下的氧化产物主要是由复杂的ZrTiO4、TiNb2O7和Nb2Zr6O17相组成，且随着氧化温度的升高，氧化产物的表面微观结构经历了致密-多孔-致密的演变过程，截面微观结构经历了致密-分层-致密的演变过程。