MICROSTRUCTURE OF ELECTRODEPOSITED Ni-W-P-SiC COMPOSITE COATINGS

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X ray diffraction data showed that the Ni W P SiC composite coatings are amorphous in plating status when their P content surpasses eight percent. The existence of SiC particles has no effect on the structure of the composite and they do not take part in the transition of the structure. The temperature of heat treatment has a considerable effect on the structure of the composite: when it is raised to 300～400 ℃, metastable Ni 5P 2 and stable Ni 3P particles would form and that would lead to precipitation hardening; when temperature increase to 400 ℃, Ni 5P 2 phases would change into Ni 3P phases. Ni 3P, Ni 5P 4, WC and a few γ (FeNi) phases are produced when Ni W P SiC composite deposits are treated through nitrocarburizing. Scanning electron microscopy showed that the distribution of SiC particles in the composite is uniform. The crystalline temperature of the composite is raised to 100 ℃ when the additive is added in the bath.