In the present work, metal-matrix composites layers reinforced by various sizes ZrC 0 . 7 particles were formed by laser single and overlapping cladding on a medium carbon steel, which are in situ synthesized by laser melting of precursor mixtures of Fe-based alloy powders and Zirconium powder using a 3 kW continuous wave CO 2 laser. A high quality coating free of cracks and porosities was obtained. Excellent bonding between the coating and the medium carbon steel substrate was ensured by the strong metallurgical bonding. The chemical compositions, surface morphology, microstructure, interface structure and the distribution of the ZrC 0 . 7 particles of the clad layers were analyzed by Optical microscopy, field emission scanning electron microscopy with associated energy dispersive X-ray spectroscopy, X-ray diffractometry, and metallography computer analysis system. The microstructure consists typically of dendrites/cells, interdendritic eutectic and dispersed ZrC 0 . 7 particles. The in situ ZrC 0 . 7 particles are distributed within dendrite and interdendritic regions owing to the trapping effect of the advancing solid-liquid interfaces. The average volume fractions of in situ ZrC 0 . 7 particles are less than 1.96% for the single clad layer, and vary from 2.2 to 3.84% for the overlapping layers respectively. The martensite (M) transformation went with the rapid cooling processes also. The microhardness profile across the cross-section of the single clad layer varies from HV 0 . 2 1000 to 1200. The microstructure of the interface between the clad layer and the substrate is martensite, which shows that there is good metallurgical bonding. The sizes and amounts of ZrC 0 . 7 particles in overlapping layers are larger and more than that of laser single clad layer.