温度对TiAl合金表面Si-Al-Y共渗层组织结构的影响

Effect of Temperature on Microstructures of Si-Al-Y Co-deposition Coatings on TiAl Alloy

通过在1000,1050,1100℃和1150℃下Si-Al-Y扩散共渗4h的方法,在TiAl合金表面制备了Y改性Si-Al共渗层,采用SEM,EDS和XRD分析了共渗温度对共渗层组织及相组成的影响。结果表明:不同温度所制备的Si-Al-Y共渗层均具有多层复合结构,共渗层的内层都是由TiAl2和γ-TiAl相组成,互扩散区为富Al的TiAl相,随温度的升高,共渗层外层和中间层的组成相都发生改变。经1000℃/4h共渗的最外层主要为TiAl3相;温度为1050℃时,由外向内依次为TiSi2外层,(Ti,X)5Si4及(Ti,X)5Si3(X表示元素Nb和Cr)中间层;1100℃和1150℃/4h条件下共渗层具有相似的结构,在1100℃/4h条件下其外层由(Ti,X)5Si4,(Ti,X)5Si3相组成;在1150℃/4h条件下其外层由(Ti,X)5Si3相组成。在四种温度条件下,1050℃/4h下制备的共渗层较厚,组织致密,适合用于Si-Al-Y共渗层的制备。

Si-Al-Y2O3co-deposition coatings on TiAl alloy were prepared by pack cementation processes at 1000,1050,1100℃and 1150℃ for 4h,scanning electron microscope（SEM）,energy dispersive spectrometry（EDS）and X-ray diffraction（XRD）were employed to investigate the surface morphologies,microstructures and phase constitutions of the coatings.The results show that the Si-Al-Y codeposition coatings have multi layer structure.All the coatings are mainly composed of a TiAl2 and γ-TiAl inner layer,and an Al rich inter-diffusion zone;the phase constituents of outer layers and middle layers of the coatings change with increasing co-deposition temperatures.The outer layer of the coating prepared at 1000℃ for 4his composed of TiAl3.However,the constituent phases change into TiSi2 in the out layer,and the middle layer is composed of（Ti,X）5Si4and（Ti,X）5Si3（Xrepresents Nb and Cr）for coating prepared at 1050℃ for 4h.The coatings prepared at 1100℃ and 1150℃ for 4h have same layer structure,and（Ti,X）5Si4,（Ti,X）5Si3phases are detected in the outer layer of the coating prepared at 1100℃,and（Ti,X）5Si3 phases are detected in the outer layer of the coating prepared at 1100℃.In the four kinds of（1000,1050,1100℃ and 1150℃）temperatures investigated,the coating prepared at 1050℃ for 4h have a denser and thicker layer,so it is selected for Si-Al-Y codeposition.