(西北工業(yè)大學(xué) 凝固技術(shù)國家重點(diǎn)實(shí)驗(yàn)室，西安710072)
摘 要: 采用Si-CeO2包埋共滲工藝于1 150 ℃在鈮硅基超高溫合金表面制備Si-Ce共滲層，分析滲劑中CeO2粉含量對(duì)共滲層組織、相組成及高溫抗氧化性能的影響。結(jié)果表明：Si-Ce共滲層的組織、結(jié)構(gòu)與單獨(dú)滲硅層的相似，由(Nb, X)Si2 (X表示Ti、Hf和Cr)外層、(Ti, Nb)5Si4過渡層和富Al擴(kuò)散層組成。EDS分析結(jié)果表明，Ce在共滲層中的分布不均勻，而在由原基體合金中的(Nb, X)5Si3塊轉(zhuǎn)變而成的富Hf (Nb, X)Si2相中含量較高。滲劑中添加CeO2不僅起到了細(xì)化滲層組織的作用，而且起到了明顯的催滲作用，當(dāng)滲劑中CeO2粉含量為3%(質(zhì)量分?jǐn)?shù))時(shí)催滲效果更顯著。Si-Ce共滲層及單獨(dú)滲硅層經(jīng)1 250 ℃氧化50 h后的氧化膜均主要由TiO2與SiO2組成。但Si-Ce共滲層試樣的氧化膜中TiO2棒更細(xì)小，并且在SiO2基體中的分布也更均勻，因而能顯著改善氧化膜的粘附性與致密性，進(jìn)而提高Si-Ce共滲層的高溫抗氧化性能。
關(guān)鍵字: 鈮硅基超高溫合金；Si-Ce共滲層；包埋滲；微觀結(jié)構(gòu)；抗氧化性能
（State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi’an 710072, China）
Abstract:Si-Ce co-deposition coatings were prepared on an Nb-silicide-based ultrahigh temperature alloy by pack cementation processes at 1 150 ℃ for 8 h. The effects of CeO2 content in pack mixtures on the microstructure, constituent phases and high temperature oxidation resistance of the coatings were studied. The results show that all coatings prepared with different contents of CeO2 in the pack mixtures are mainly composed of a (Nb, X)Si2 (X represents Ti, Hf and Cr) outer layer, a (Ti, Nb)5Si4 transitional layer and an Al-rich diffusion zone, which are similar to that of purely siliconized coatings. EDS analysis reveals that the distribution of Ce in the co-deposition coatings is not uniform. The content of Ce in the Hf-rich (Nb, X)Si2 phase transferred from (Nb, X)5Si3 in the base alloy is higher than that in other phases. The addition of CeO2 in the pack mixtures not only refines the microstructure of the coatings, but also obviously catalyzes the coating growth, especially when 3% CeO2 (mass fraction) is added in the pack mixtures. Both scales formed on the Si-Ce co-deposition coating and purely siliconized coating after oxidation at 1 250 ℃ for 50 h are mainly composed of TiO2 and SiO2. However, much finer TiO2 rods are observed distributing evenly in the scale of the Si-Ce co-deposition coating after oxidation. Thus, the Si-Ce co-deposition coatings enhance the high temperature oxidation resistance due to the improved compactness of the protective oxide scale.
Key words: Nb-silicide-based ultrahigh temperature alloy; Si-Ce co-deposition coatings; pack cementation process; microstructure; oxidation resistance
