(西北工業(yè)大學 凝固技術國家重點實驗室，西安 710072)
摘 要: 采用Si-Y2O3包埋共滲工藝在鈮硅化物基超高溫合金表面制備Y改性的硅化物涂層，共滲溫度分別為 1 050、1 150和1 250 ℃，共滲時間分別為5、10、15和20 h。利用SEM、EDS和XRD等方法分析涂層的結構、元素分布及相組成，并對涂層形成機理及Y2O3催滲機理進行討論。結果表明：涂層具有明顯分層的結構，由外至內(nèi)依次為(Nb, X)Si2(X表示Ti、Hf和Cr)外層和(Nb, X)5Si3過渡層，在過渡層與基體之間有一些不連續(xù)分布的細小(Cr, Al)2(Nb, Ti)塊狀沉淀；Y在涂層中的分布不均勻，在(Cr, Al)2(Nb, Ti)相中Y含量為0.94%(摩爾分數(shù))左右，而在(Nb, X)Si2和(Nb, X)5Si3相中則為0.46%~0.57%；隨共滲溫度升高，Y含量增加顯著；而隨共滲時間延長，涂層中的Y含量增加較小；滲劑中添加Y2O3不但細化了涂層的組織，而且產(chǎn)生了明顯的催滲作用。
關鍵字: 鈮硅化物基超高溫合金；Si-Y2O3共滲涂層；包埋滲；Y2O3；組織形成
（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
