Ti_2AlNb合金表面等离子渗铝层的抗高温氧化性能

High Temperature Oxidation Properties of Surface Aluminized Layer on Ti_2AlNb Alloy

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。

Surface aluminized layer was prepared on a Ti2AlNb alloy by double-glow discharge plasma surface technique. The kinetic data of oxidation mass gain were measured for the alloys with and without aluminized layer at 650, 750 and 850 ℃ respectively, and the oxidation rate constants at different temperatures were determined by the relevant linear fitting. The microstructure and phase composition of the formed oxide scale were analyzed by XRD and SEM. It was found that aluminized layer consisted of compact deposited layer and Al-Ti-Nb diffusion layer. At each temperature, the aluminized alloy exhibited parabolic oxidation kinetics and the oxidation rate constant was lower than that of the blank ones. The aluminized layer significantly improved oxidation resistance of Ti2AlNb alloy due to the formation of a dense and continuous Al2O3-rich scale. The inter-diffusion layer provided protection for the substrate from high temperature oxidation and intergranular embrittlement.