及其组织形成
(西北工业大学 凝固技术国家重点实验室，西安 710072)
摘 要: 利用包埋渗法在铌基合金上制备抗氧化硅化物涂层，渗硅温度分别为1 050、1 150和1 250 ℃，渗硅时间分别为2、5、10、15和20 h。利用SEM、EDS和XRD等检测手段分析涂层的结构、元素分布及相组成等，并对涂层形成的反应机理及反应动力学进行讨论。结果表明：涂层的相组成为(Nb, X)Si2(X表示Ti, Cr, Hf和Al等元素)；涂层具有双层结构，且上层较为致密；涂层与基体之间达到了冶金结合，通过扩散形成过渡层及互扩散区；在包埋渗温度分别为1 050、1 150和1 250 ℃时，涂层生长的动力学曲线均符合抛物线规律。
关键字: 铌基合金；包埋渗；涂层；过渡层；互扩散区；反应动力学
oxidation-resistant silicide coatings on
Nb-based alloy by pack cementation technique
（State Key Laboratory of Solidification Processing,
Northwestern Polytechnical University, Xi’an 710072, China）
Abstract:Oxidation-resistant silicide coatings on an Nb-based alloy were prepared by pack cementation technique. The holding temperatures were 1 050, 1 150 and 1 250 ℃ and the holding time were 2, 5, 10, 15 and 20 h, respectively. The structure, phase constituents and compositional distribution in the coatings were analyzed by SEM, EDS and XRD techniques. The formation mechanism and growth kinetics of the coatings were discussed and measured. The results show that the phase constituent of the coatings is (Nb, X)Si2 (X represents Ti, Cr, Hf and Al elements). Double layers exist in the coatings, and the upper layer is denser. A transitional layer and a diffusion zone form between the coating and base material. The coating growth kinetics at 1 050, 1 150 and 1 250 ℃ were all fitted well to parabolic laws.
Key words: Nb-based alloy; pack cementation; coating; transitional layer; diffusion zone; reaction kinetics
