(1. 湖南工程學院 機械工程學院，湘潭 411101；
2. 中南大學 材料科學與工程學院，長沙 410083)
摘 要: 采用電弧離子鍍(AIP)在Ti-6.48Al-0.99Mo-0.91Fe (質量分數(shù)，%) 鈦合金表面制備Ta-10W (質量分數(shù)，%)涂層。通過真空熱處理試驗、X射線衍射分析(XRD)、掃描電鏡(SEM)與能譜(EDS)分析、透射電鏡(TEM)分析、電子探針分析(EPMA)等方法，研究純熱暴露下Ta-W涂層/鈦合金體系的相組成、顯微組織形貌、元素分布、界面行為等，評估了體系熱穩(wěn)定性能。結果表明：純熱暴露過程中，Ta-W涂層相組成無明顯變化，均由多晶α-Ta(W)組成，其平均晶粒尺寸由沉積態(tài)的46 nm小幅增至750 ℃時的49 nm和950 ℃時的51 nm，涂層表現(xiàn)出良好的相穩(wěn)定性；由于元素Ta、Ti在Ta-Ti體系中擴散系數(shù)的差異及難熔金屬元素Ta、W良好的穩(wěn)定性，Ta-W涂層/鈦合金體系呈現(xiàn)出良好的界面及元素穩(wěn)定性：涂層中元素Ta、W始終維持在接近沉積態(tài)含量水平，無快速擴散、固溶于基體而失效的行為，體系僅在界面形成互擴散層，無空洞、裂紋缺陷和金屬間化合物的形成；由于元素互擴散的加劇及涂層元素在α-Ti、β-Ti中的固溶度差異，鈦合金基體同素異晶轉變溫度(ATT)對體系界面和元素穩(wěn)定性影響明顯；純熱暴露過程中，Ta-W涂層有效厚度保持穩(wěn)定、無明顯變化。基于Fick定律，獲得550、750和950 ℃時互擴散層厚度與時間的關系式。
關鍵字: Ta-W涂層；鈦合金；純熱暴露；熱穩(wěn)定性；真空熱處理
（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
