NiCrBSi coating was prepared on the surface of 45 steel with 5 kW TJ-HL-T5000 CO2 laser by powder metallurgy. The microstructure and properties of the cladding layer were characterized by SEM （scanning electron microscope）、EDX（energy dispersive X-ray）、XRD （X-ray diffraction）. The micro-hardness and wear resistance of the laser cladding layer were examined by microhardness meter and M-200 ring-block wear tester. The results show that laser cladding layer with the good metallurgical bonding between the coating and substrate and dense

uniform

continuous and free of pores and cracks can be observed based on the optimized processing parameters. The microstructure of the cladding coating is mainly composed of dendrite γ-Ni、eutectic Ni3B、bulky particles CrB and dendrite Cr23C6 particles. The microhardness of the cladding coating （HV0.2）500～650 is approximately 2 times than that of the substrate（HV0.2）250

which is attributed to particle strengthening and grain-refining strengthening effects

greatly improving wear resistance of 45 steel.