Preparation and tribological properties of novel cold-sprayed Ti-diamond composite coating

Attaining a high deposition efficiency and uniform distribution of the reinforced phase in cold-sprayed composite coatings has always been challenging. In the present study, a Ti-diamond composite powder was prepared via ball milling, followed by the deposition of a composite coating onto a Ti6Al4V substrate using cold-spraying technology. X-ray diffraction analysis confirmed that neither alpha-Ti nor diamond phases underwent a phase transformation during the ball milling or spraying processes. Scanning electron microscopy revealed that the irregular diamonds in the composite coating powder were uniformly coated on the surface of the spherical Ti particles, leading to a homogeneous dispersion of the diamonds within the coating. Energy-dispersive X-ray spectroscopy indicated that metallurgical and chemical bonding occurred between the diamond and Ti, and microhardness and bonding strength test results revealed that the hardness of the coating increased with the diamond content. Friction and wear analyses indicated that the wear resistance of the composite coating was better than that of a pure Ti coating, and the wear rate of the coating was the lowest when the diamond content of the coating was 10 wt%. Morphological and composition analyses of the worn surfaces of the composite coatings suggested that some of the Ti was oxidized into TiO2 during the wear process, and the diamond lost its support owing to the wear and spalling of Ti. Finally, abrasive wear occurred under the joint action of TiO2 and shed diamond.