(西北工业大学 凝固技术国家重点实验室，西安 710072)
摘 要: 采用Si-Y2O3包埋共渗工艺在铌硅化物基超高温合金表面制备Y改性的硅化物涂层，共渗温度分别为 1 050、1 150和1 250 ℃，共渗时间分别为5、10、15和20 h。利用SEM、EDS和XRD等方法分析涂层的结构、元素分布及相组成，并对涂层形成机理及Y2O3催渗机理进行讨论。结果表明：涂层具有明显分层的结构，由外至内依次为(Nb, X)Si2(X表示Ti、Hf和Cr)外层和(Nb, X)5Si3过渡层，在过渡层与基体之间有一些不连续分布的细小(Cr, Al)2(Nb, Ti)块状沉淀；Y在涂层中的分布不均匀，在(Cr, Al)2(Nb, Ti)相中Y含量为0.94%(摩尔分数)左右，而在(Nb, X)Si2和(Nb, X)5Si3相中则为0.46%~0.57%；随共渗温度升高，Y含量增加显著；而随共渗时间延长，涂层中的Y含量增加较小；渗剂中添加Y2O3不但细化了涂层的组织，而且产生了明显的催渗作用。
关键字: 铌硅化物基超高温合金；Si-Y2O3共渗涂层；包埋渗；Y2O3；组织形成
（State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi’an 710072, China）
Abstract:Si-Y2O3 co-deposition coatings on an Nb-silicide-based ultrahigh temperature alloy were prepared by pack cementation processes at 1 050, 1 150 and 1 250 ℃ for 5, 10, 15 and 20 h, respectively. The coating structure, phase constituents and compositional distribution were investigated by SEM, EDS and XRD. Both the formation mechanism and growth kinetics of coatings and the catalysis mechanism of Y2O3 were discussed. The results show that all Si-Y2O3 co-deposition coatings are composed of a (Nb, X)Si2 (X represents Ti, Hf and Cr elements) outer layer and a (Nb, X)5Si3 transitional layer. Some thin discontinuous (Cr, Al)2(Nb, Ti) Laves precipitates form between the substrate and (Nb, X)5Si3 transitional layer. The distribution of Y in the coatings is not uniform. The content of Y in (Nb, X)Si2 and (Nb, X)5Si3 phases is about 0.46%−0.57% (molar fraction) while that in (Cr, Al)2(Nb, Ti) is about 0.94%. With increasing co-deposition temperature, the content of Y increases obviously, while it increases slightly with the prolonging co-deposition time. The addition of Y2O3 in the pack mixtures not only refines the microstructure of the coatings, but also obviously catalyzes the coating growth.
Key words: Nb-silicide-based ultrahigh temperature alloy; Si-Y2O3 co-deposition coatings; pack cementation process; Y2O3; structure formation
