Abstract: In-situ synthesis of TiB₂ ceramic particle reinforced Ni-base alloy composite coating has been conducted on 45 steel surface by CO₂ flow transverse laser.X-ray diffraction analysis shows γ-(Ni,Fe) solid-solution and ceramic phase mainly of TiB₂ in the coating.Scanning electron microscope,energy dispersive spectroscopy and electron probe microanalysis show that the dendrites dispersed homogeneously in the coating are very thin.The mierostructure and composition in the dendrites are evidently different from that in the intergranular.The mierostructure in the heat-affected zone is mainly composed of blended martensite.The microhardness of the coating increases substantially compared to that of the matrix.