Abstract: Si-Y co-deposition coatings were prepared on an TiAlNb9 alloy by pack cementation processes at 1 080 ℃ for 5 h, scanning electron microscope, energy dispersive spectrometry and X-ray diffraction were employed to investigate the microstructure and constituent phases of the co-deposition coatings, and the friction and wear properties of both base alloy and the coatings sliding against GCr15 were comparatively investigated. The results show that the obtained coating with a thickness about 33 μm was uniform, continuous and compact. The outer layer of the coating was mainly composed of (Ti, Nb)Si₂. The middle layer was divided into two layers: the upper portion was composed of (Ti, X)₅Si₄, and the lower portion was composed of (Ti, X)₅Si₃. The inner layer was mainly composed of γ-TiAl. The wear resistance of the Si-Y co-deposition coating was obviously superior to that of TiAlNb9 alloy under the experimental conditions, and the wear mechanisms of TiAlNb9 alloy were ploughing and abrasion. Unmeasurable wear of the Si-Y co-deposition coating was due to its much higher micro-hardness than the GCr15 counterpart.