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利用双辉等离子表面冶金技术在Ti2AlNb合金表面制备渗铝层,测定渗铝样品和空白样品在650,750和850℃下空气中的氧化增重动力学数据,通过线性拟合获取试样在不同温度下的氧化速率常数。采用SEM和XRD分析氧化膜的组成与结构。探讨高温下渗铝层提高Ti2AlNb合金抗高温氧化性能的机理。结果表明:双辉等离子渗Al后,在Ti2AlNb合金表面形成梯度渗铝层,显著地提高了Ti2AlNb合金在高温下的抗氧化性能。在各实验温度下,渗铝样品的氧化曲线近似呈抛物线规律,其平均氧化速率都低于所对照的空白样品。在850℃氧化100 h后,渗铝样品表面形成致密的保护性富Al2O3膜,有效地阻止膜层内部进一步氧化。中间的扩散层也起到保护基体、改善晶间脆性的作用。
The aluminized layer was prepared on the surface of Ti2AlNb alloy by double-glow plasma surface metallurgy. The kinetic data of oxidation weight gain of aluminized samples and blank samples in air at 650, 750 and 850 ℃ were measured. The samples were obtained by linear fitting at different temperatures Of the oxidation rate constant. The composition and structure of the oxide film were analyzed by SEM and XRD. The mechanism of high temperature aluminizing layer to improve the high temperature oxidation resistance of Ti2AlNb alloy was discussed. The results show that the formation of a gradient aluminized layer on the surface of Ti2AlNb alloy after double hull plasma infiltration can significantly improve the oxidation resistance of Ti2AlNb alloy at high temperature. At each experimental temperature, the oxidation curves of aluminized samples are approximately parabolic, and the average oxidation rates are lower than those of the blank samples. After oxidation at 850 ℃ for 100 h, a dense and protective Al2O3-rich film was formed on the surface of aluminized samples, which effectively prevented further oxidation inside the film. The middle of the diffusion layer also plays a role in protecting the substrate and improving intergranular brittleness.