Abstract:The nano-crystalline NiSi2/Ti5Si3 composite coating was prepared on TC4 alloy substrate surface by double cathode glow discharge technology. The composition and microstructure of the nano-crystalline composite coating were analyzed by XRD, SEM and TEM. Nanoindentation and scratch test were used to assess its hardness, elastic modulus and adhesion property between the coating and the substrate. The results indicate that the nano-crystalline NiSi2/Ti5Si3 composite coating is composed of two different layers, NiSi2 deposition layer with average grain size of 40 nm, which is the outer layer of 7 μm thickness, and Ti5Si3 diffusion layer with average grain size of 70 nm which is the inner layer of 3 μm thickness. A large number of twins are found in the diffusion layer. The nano-crystalline NiSi2/Ti5Si3 composite coating combines closely with TC4 alloy substrate with an adhesive strength of 49 N and the hardness of the composite coating presents gradient distribution. The specific wear rate of the nano-crystalline NiSi2/Ti5Si3 composite coating is one order of magnitude lower than that of TC4 alloy, and the composite coating is very insensitive to the test load and temperature. Compared with TC4 alloy, the corrosion current density of the nanocrystalline NiSi2/Ti5Si3 composite coating is decreased by two orders of magnitude. The Nyquist plots of the nanocrystalline NiSi2/Ti5Si3 composite coating consist of single capacitance arc with a higher value