(哈爾濱工業(yè)大學(xué)現(xiàn)代焊接生產(chǎn)技術(shù)國家重點實驗室， 哈爾濱 150001)
摘 要: 通過使用高能量密度的電子束高速掃描預(yù)先涂有Si粉的TiAl合金表面， “原位”制得了以高硬度金屬間化合物Ti5Si3為增強相、 以TiAl、 Ti3Al為基體的復(fù)相合金表面改性層。 利用光學(xué)顯微鏡、 電子探針、 能譜儀及X射線衍射儀分析和研究了電子束表面改性層的顯微組織結(jié)構(gòu)； 同時測試了沿改性層深度方向的硬度分布。 結(jié)果表明： 表面改性層由TiAl、 Ti3Al、 Ti5Si3相組成， Ti5Si3相的形態(tài)及分布沿層深方向呈現(xiàn)梯度變化， 在表層為粗大的六棱柱狀結(jié)構(gòu)， 沿改性層向內(nèi)， 其中、 下部由于冷卻速度相對較快， 硬質(zhì)相的形態(tài)及分布趨于細小、 密集； 改性層與基體間沒有明顯的界面， 為完全的冶金結(jié)合； 改性層具有較高的硬度， 顯微硬度最高達到895， 約為基體的3倍。
關(guān)鍵字: 電子束表面改性； γ-TiAl合金； Ti5Si3； 顯微組織； 顯微硬度
（ State Key Laboratory of Advanced Welding Production Technology,Harbin Institute of Technology,
Harbin 150001, China）
Abstract: In-situ Ti5Si3/ Ti3Al/TiAl composite coatings reinforced by high hardness Ti5Si3 intermetallic phase were fabricated on γ-TiAl substrates precoated with silicon powders by means of electron beam surface alloying. The microstructure characteristics of the composite coatings were investigated using optical microscope, electron probe microanalysis, energy spectrometer and X-ray diffraction. Micro-hardness was measured from the surface down to the substrate by a Vickers hardness tester. The results show that composite coatings are composed of TiAl, Ti3Al and Ti5Si3 phases. More specifically, the morphology and distribution of Ti5Si3 phase change with gradient transition along the depth of the coatings. In the upper level of the coatings, a considerable amount of large hexagonal-pillar-shaped Ti5Si3 phases were observed, while in the middle and lower level of the coatings, the particles get smaller and denser because of faster cooling speed. The bond zone between the substrate and the coatings is wholly metallurgical bonding with no apparent interface. As for the hardness of the composite coatings, it is higher than that of the substrate, its maximum value reaches 895, nearly triple the value of the matrix one.
Key words: electron beam surface alloying; γ-TiAl alloy; Ti5Si3; microstructure; micro-hardness
