Abstract: Titanium carbide reinforced titanium-based cladding coating with rare earth CeO₂ on Ti6Al4V surface is successfully prepared by the coaxial powder-feeding laser cladding technology. The forming quality, microstructure, element distribution, hardness, and friction and wear properties are investigated by penetration inspection, optical microscopes, X-ray diffractometers, scanning electron microscopes, energy spectrum analyzers, electro-probe microanalyzers, microhardness, and friction and wear testing methods. The results show no crack defects in the coating, with only a few pores distributed in the interlayer transition zone (the porosity rate 1.65%). The main phases of the coating include β solid solution (CrTi₄) which is rich in Ti and Cr elements, vacant titanium carbide (TiC_x) and rare earth oxide (CeO₂). Significant differences exist in the morphologies of titanium carbides in different zones of the cladding coating. The titanium carbides in the top and middle zones of the cladding coating exhibit well-developed dendritic and needle-like shapes, while the bonding zone consists of needle-like and small-sized undeveloped dendrites. The distribution of the carbon element in the titanium carbide dendrites is relatively heterogeneous, and the carbon content of the primary dendrites is higher than that of the secondary dendrites. Ni and Cr elements in the matrix phase present an obvious segregation phenomenon, while the distribution of Al and V elements are relatively uniform. In addition, rare earth oxide CeO₂ is mainly distributed at the interphase boundary between TiC_x and CrTi₄ as well as the CrTi₄ grain boundary. Compared with the substrate, although the TiC_x reinforced titanium-based composite coating exhibits a higher friction coefficient, the wear resistance is significantly increased (by nearly 52%). Both the wear mechanisms of the cladding coating and the substrate are of composite wear modes combining adhesive wear with abrasive wear; however, the cladding coating displays a lighter degree.

Key words: titanium alloy, laser cladding, TiC_x, CrTi₄, CeO₂, friction and wear