Characterization of Gradient Ni-Fe/SiC Composite Coating on Mild Steel by Thermal Spraying in Combination with Laser Cladding

Metal matrix composite coating Ni-Fe/SiC was prepared on an iron-based substrate by thermal spraying combined with laser cladding, using SiC particulates as the reinforcing agent. The microstructures of the coatings formed at different thermal spraying and laser cladding conditions were characterized by means of X-ray diffraction and electron probe microanalysis. The thermal oxidation properties of the mixed powders composed of different content of SiC particulates and relevant Ni-based alloy as the balance were examined using differential scanning calorimetry. The hardness profile of the thermal sprayed and laser cladding coatings was investigated as well. It was found that SiO2 particulates were generated and dissolved and dispersed during the melting and solidification of the laser cladding process, which was ascribed to the oxidation of the dispersed SiC particulates. The micro-hardness depth profile of the target laser cladding composite coating was characterized by gradient distribution, which could be related to the gradient distribution of the hard SiC and SiO2 particulates in the dendrites and interdendrites of the cladding layer. Both SiC and SiO2 particulates contributed to greatly increasing the microhardness and mechanical properties of the titled laser cladding composite coatings.