Abstract: Metal matrix composite layers reinforced by in situ WC particles were formed by laser cladding using pre pasted (1.2%Zr+40%WC)/FeCSiBRE alloy powder on the medium carbon steel substrate.The morphologies,microstructures,interface structure and the distribution of the WC particles in the clad layers were observed with optical microscope,scanning electron microscope with EDAX.The microstructure characteristics of metal matrix composites are the typical γ austenite dendrite distributed on the eutectic substrate.In situ WC particles can not only be trapped by the advanced solid/liquid interface and distribute within dendrite,but also be pushed away by the interface into interdendritic regions together with the eutectics.The martensite transformation is observed after the rapid cooling processes also.There is good metallurgical bonding between the layer and substrate.The microhardness varies between 500~600 HV 0.2.