Electroless Ni–P–SiC composite coatings with superfine particles

Superfine silicon carbide (SiC) particles reinforced nickel–phosphorus (Ni–P) matrix composite (Ni–P–SiC) coatings were prepared by electroless plating. The morphology and structure as well as the phase transformation of the composite coatings with three sizes of SiC particles were studied by scanning electron microscopy (SEM), differential scanning calorimetry (DSC), X-ray diffraction (XRD) and transmission electron microscopy (TEM), respectively. It was shown that SiC particles co-deposited homogeneously, and the structure of Ni–P–SiC composite coatings as deposited was amorphous. After certain heat treatment, the matrix of composite coatings crystallized into nickel crystal and nickel phosphide (Ni3P). At the higher temperature nickel reacted with SiC, and nickel silicides with free carbon were produced. The reaction temperature in electroless composites coatings decreased with the decrease in the size of SiC particles. Microhardness of electroless Ni–P–SiC composite coatings increased due to the existence of particles, and reached to the maximum value after heat treatment at 400 °C for 1 h.