The Cr-modified silicide coatings were prepared on Ti-Nb-Si based ultrahigh temperature alloy by Si-Cr co-deposition processes at 1 250, 1 350 and 1 400 ℃ for 10 h, respectively. The results show that the Si-Cr co-deposition coatings have multi layer structure. The phase constituents of outer layers and intermediate layers of the coatings change with increasing co-deposition temperatures. The outer layer and intermediate layer of the coating prepared at 1 250 ℃ for 10 h consist of (Ti, X)_5Si_3 (X represents Nb, Hf and Cr elements) and (Ti, X)_5Si_4, respectively. The transitional layer of this coating is very thin and composed of (Ti, X)_5Si_3. The content of Cr increases significantly in the outer layer of the coating prepared at 1 350 ℃ for 10 h, and (Nb_(1.95)Cr_(1.05))Cr_2Si_3 ternary phase forms in this layer besides (Ti, X)_5Si_3 phase. The intermediate layer is composed of (Ti, X)_5Si_4 and (Ti, X)_5Si_3 phases, and the transitional layer composed of (Ti, X)_5Si_3 phase is thickened obviously. (Nb_(1.95)Cr_(1.05))Cr_2Si_3 ternary phase is the single phase constituent in the outer layer of the coating prepared at 1 400 ℃ for 10 h, and the intermediate layer is composed of (Ti, X)_5Si_3 thoroughly. Discontinuous (Nb, Ti)_3Si blocks are also found between the transitional layer and substrate. The influence of temperature on the diffusion ability of Cr atoms is greater than that of Si atoms in the Si-Cr co-deposition processes investigated.%采用在1 250、1 350和1 400 ℃ Si-Cr包埋共渗10 h的方法,在Ti-Nb-Si基超高温合金表面制备了Cr改性硅化物涂层.结果表明:各温度下制备的涂层均具有多层复合结构;随包埋共渗温度的升高,涂层外层和中间层的组成相都发生改变.经1 250 ℃,10 h Si-Cr共渗时涂层外层为(Ti, X)_5Si_3(X代表Nb、Hf和Cr元素),中间层为(Ti, X)_5Si_4,过渡层(Ti, X)_5Si_3很薄;当提高共渗温度至1 350 ℃时,涂层外层中Cr含量明显提高,外层除了(Ti, X)_5Si_3外,还出现含Cr的三元相(Nb_(1.95)Cr_(1.05))Cr_2Si_3,中间层由(Ti, X)_5Si_4和(Ti, X)_5Si_3两相组成,而过渡层((Ti, X)_5Si_3)增厚;继续提高共渗温度至1 400 ℃时,涂层外层主要由(Nb_(1.95)Cr_(1.05))Cr_2Si_3三元相组成,中间层已全部由(Ti, X)_5Si_3相组成,在过渡层与基体间还存在不连续的块状(Nb, Ti)_3Si相,Si-Cr共渗温度对Cr扩散的影响更为显著.
展开▼
