Crystallization characteristics of Ni-W-P composite coatings reinforced by CeO2 and SiO2 nano-particles

Abstract

Ni-W-P composite coatings reinforced by CeO2 and SiO2 nano-particles on the surface of common carbon steels, were prepared by double pulse electrodeposition. The crystallization course was characterized by phase structures, crystallinity, grain sizes and microstructures. The results indicate that as-deposited composite coating is amorphous. Whereas it turns into the crystalline structure with 98.25% crystallinity, and Ni3P, Ni2P and Ni5P2 alloy phases precipitate from structures at 400 °C. Thereafter, Ni2P and Ni5P2 metastable alloy phases turn into Ni3P stable alloy phase at 500 °C. The crystallization course of the composite coating has finished when being heat-treated at 700 °C. The average sizes of Ni grains increase with the rise of heat treatment temperature from 400 °C to 700 °C. CeO2 and SiO2 nano-particles deposited into Ni-W-P alloys can delay the crystallization course and habit the growth of alloy phases.