及其組織形成
(西北工業(yè)大學(xué) 凝固技術(shù)國(guó)家重點(diǎn)實(shí)驗(yàn)室，西安 710072)
摘 要: 利用包埋滲法在鈮基合金上制備抗氧化硅化物涂層，滲硅溫度分別為1 050、1 150和1 250 ℃，滲硅時(shí)間分別為2、5、10、15和20 h。利用SEM、EDS和XRD等檢測(cè)手段分析涂層的結(jié)構(gòu)、元素分布及相組成等，并對(duì)涂層形成的反應(yīng)機(jī)理及反應(yīng)動(dòng)力學(xué)進(jìn)行討論。結(jié)果表明：涂層的相組成為(Nb, X)Si2(X表示Ti, Cr, Hf和Al等元素)；涂層具有雙層結(jié)構(gòu)，且上層較為致密；涂層與基體之間達(dá)到了冶金結(jié)合，通過(guò)擴(kuò)散形成過(guò)渡層及互擴(kuò)散區(qū)；在包埋滲溫度分別為1 050、1 150和1 250 ℃時(shí)，涂層生長(zhǎng)的動(dòng)力學(xué)曲線均符合拋物線規(guī)律。
關(guān)鍵字: 鈮基合金；包埋滲；涂層；過(guò)渡層；互擴(kuò)散區(qū)；反應(yīng)動(dòng)力學(xué)
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
