Microstructure and Tribological Properties of Ni-Based Laser-Clad Coatings by Rare Earth Modification

TiC + TiB2 + Ti2Ni-reinforced Ni-based laser-clad coatings were prepared on Ti-6Al-4V by CeO2 modification. The forming quality, microstructure, element distribution, microhardness and wear resistance of the coatings were studied. The results showed that adding 2 wt.% CeO2 effectively eliminated cracks but led to the micro-pores. The coatings mainly consisted of TiC, TiB2, Ti2Ni and matrix alpha-Ti. When 2 wt.% CeO2 was added, the coating microstructure was remarkably refined, uniform and dense, and exposed surface area of matrix decreased. TiC changed from dendritic to petal-shaped and granular, TiB2 from long rod-shaped to short rod-shaped, Ti2Ni from irregular bulk-like to microporous irregular bulk-like. Al, Cr, Fe and Si distributed uniformly in the Ni-rich matrix, and V was mainly segregated on the TiB2. Ce2O3 particles formed by the decomposition of CeO2 in the coating mainly distributed around TiC. The planar lattice disregistry delta between the interface (101 over bar 0) of Ce2O3 and the interface (110) of TiC was 4.00%, and Ce2O3 could act as the nucleation substrate to effectively refine TiC. With the addition of CeO2, the microhardness was increased, and the wear depth, wear volume and friction coefficient were decreased. 2CeO(2) coating exhibited the best wear resistance and anti-friction compared with 0CeO(2) coating and exhibited an abrasive wear pattern.