High-Temperature Tribological Properties of Laser Clad Composite Coatings on Ti6Al4V Alloy

Wear resistant composite coatings were deposited on Ti6Al4V alloy substrate with the preplaced NiCrBSiFe alloy powders by laser cladding. Microstructure, micro-hardness, room-temperature (25 ℃) and high-temperature (600 ℃) wear resistance of the laser clad composite coatings were determined. The results show that the composite coating were composed of γ-(Ni, Cr, Fe) solid solution matrix and TiC, TiB₂ and CrB reinforced particulates, which were uniformly distributed in the coating. The metallurgical bonding between cladding coating and substrate was observed. The average micro-hardness of the composite coating was HV_0.5950, which was almost three times higher than that of the substrate (HV_0.5360). At room-temperature, the composite coating possessed excellent tribological properties due to its relatively high hardness. At high-temperature, the friction coefficient and wear rate of Ti6Al4V alloy all reduced because of the formation of TiO₂ oxide scales and the solid lubrication effect. Due to the reduction of micro-hardness of the composite coating, some wear debris and plowing grooves occurred on the worn surfaces of the composite coating. The friction coefficient and wear rate of the composite coating increased slightly. Compared with the Ti6Al4V alloy, the laser clad composite coating exhibited better wear-resisting capability at room temperatures and 600 ℃.