(1. 湖南工程学院 机械工程学院，湘潭 411101；
2. 中南大学 材料科学与工程学院，长沙 410083)
摘 要: 采用电弧离子镀(AIP)在Ti-6.48Al-0.99Mo-0.91Fe (质量分数，%) 钛合金表面制备Ta-10W (质量分数，%)涂层。通过真空热处理试验、X射线衍射分析(XRD)、扫描电镜(SEM)与能谱(EDS)分析、透射电镜(TEM)分析、电子探针分析(EPMA)等方法，研究纯热暴露下Ta-W涂层/钛合金体系的相组成、显微组织形貌、元素分布、界面行为等，评估了体系热稳定性能。结果表明：纯热暴露过程中，Ta-W涂层相组成无明显变化，均由多晶α-Ta(W)组成，其平均晶粒尺寸由沉积态的46 nm小幅增至750 ℃时的49 nm和950 ℃时的51 nm，涂层表现出良好的相稳定性；由于元素Ta、Ti在Ta-Ti体系中扩散系数的差异及难熔金属元素Ta、W良好的稳定性，Ta-W涂层/钛合金体系呈现出良好的界面及元素稳定性：涂层中元素Ta、W始终维持在接近沉积态含量水平，无快速扩散、固溶于基体而失效的行为，体系仅在界面形成互扩散层，无空洞、裂纹缺陷和金属间化合物的形成；由于元素互扩散的加剧及涂层元素在α-Ti、β-Ti中的固溶度差异，钛合金基体同素异晶转变温度(ATT)对体系界面和元素稳定性影响明显；纯热暴露过程中，Ta-W涂层有效厚度保持稳定、无明显变化。基于Fick定律，获得550、750和950 ℃时互扩散层厚度与时间的关系式。
关键字: Ta-W涂层；钛合金；纯热暴露；热稳定性；真空热处理
（1. School of Mechanical Engineering, Hunan Institute of Engineering, Xiangtan 411101, China;
2. School of Materials Science and Engineering, Central South University, Changsha 410083, China）
Abstract:Ta-10W (mass fraction, %) coating was deposited on Ti-6.48Al-0.99Mo-0.91Fe (mass fraction, %) titanium alloy by arc ion plating (AIP). Vacuum heat treatment, XRD, SEM, EDS, TEM and EPMA analysis were carried out to study the phase composition, microstructure, elements distribution and interface behavior of the Ta-W coating/titanium alloy substrate system under pure thermal exposure. The thermal stability of the coating/substrate system was also evaluated. The results show that the coating/substrate system exhibits satisfying phase composition stability during the pure thermal exposure. The Ta-W coating always consists of polycrystalline α-Ta(W) without changes of phase composition before and after pure thermal exposure. Only a small increase in average grain size of the Ta-W coating, from 46 nm of as-deposited coating to 49 nm at 750 ℃ and 51 nm at 950 ℃, was observed. The coating/substrate system exhibits satisfying interface and element stability during the pure thermal exposure for the different diffusion coefficient of Ta and Ti in Ta-Ti binary system and the good stability of refractory metals of Ta and W. The Ta-W coating maintains as high Ta and W content level as the as-deposited coating without degradation due to the fast diffusion and solution into the titanium ally substrate. Only an inter-diffusion layer develops at the interface without the formation of voids, cracks and intermetallics. The allotropic transformation temperature (ATT) of the titanium alloy substrate has a significant influence on the coating/substrate system interface and element stability due to the different solid solubility of Ta and W inα-Ti and β-Ti or/and more violent element inter-diffusion. Compared with the as-deposited coating, the thickness of Ta-W coating maintains stability and shows no obvious changes during the pure thermal exposure. Based on Fick’s law, the relationship between the thickness of inter-diffusion layer and time at 550 ℃, 750 ℃ and 950 ℃ was discussed.
Key words: Ta-W coating; titanium alloy; pure thermal exposure; thermal stability; vacuum heat treatment
