The WC reinforced Fe-based amorphous composite coatings were prepared by laser cladding with rectangular spot. The effect of laser remelting on the microstructure and properties of composite coatings was investigated. The results showed that laser remelting can reduce the cracks and porosities of the cladding coating and improve its surface quality. Large amounts of crystalline phases were precipitated at the top of the cladding and remelting coatings. However, the microstructure at the top of the remelting coating was finer compared to that at the top of the cladding coating. With increasing distance from the surface of substrate, the amorphous phase appeared within the remelting coating and large amounts of carbides rich in Fe and Mo, Fe 23 B 6 , c-Fe and Cr 9.1 Si 0.9 phases were also precipitated in the remelting coating. As a result, the corrosion resistance of the remelting coating was higher than that of the cladding coating. The microhardness of the remelting coating was approximately 1.13 times higher than that of the cladding coating.

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a b s t r a c tThe first-principles calculations were performed based on density functional theory to study the structural, electronic and magnetic properties of Ni 4 C resulting from carbon atom diffusion in a conventional Ni unit cell. Firstly, geometry optimization was performed to reach the equilibrium state of Ni 4 C. The lattice constant of the stable Ni 4 C crystal structure was larger than that of the Ni unit cell. Then the electronic and magnetic properties of Ni 4 C were determined, and the results showed that the magnetic moment was 0.46 m B per unit cell, and the calculated local magnetic moment of carbon atoms was 0. There were two occupied sites for Ni atoms with different local magnetic moments, which was about 0.64 m B (close to that of nickel unit cell) for Ni a atoms at the top corners and a negative value of À0.06 m B for Ni b atoms at the face center. The magnetic moment increased abruptly to 1.89 m B at 3.79 Å due to the changes of lattice parameters with external factors, and fluctuated slowly from 3.5 Å to 3.78 Å.

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