In Situ Synthesis of Nanoscale WC-η Composite Powder and its Application in Cermet Coating

摘要

Nanoscale WC-η composite powder was synthesized by in situ reaction of tungsten oxide, cobalt oxide and carbon black mixtures for fabricating the nanostructured WC-based coating in which the conventional Co matrix was substituted for η phases (i.e. Co_6W_6C, Co_3W_3C, Co_2W_4C, etc) due to their excellent corrosion resistance to molten zinc. The effects of the carbon addition of the raw powders and the temperature on the phase constitutions of the as-synthesized composite powders have been investigated. Subsequently, the powder was agglomerated and heat-treated to prepare the feedstock for high velocity oxy-fuel (HVOF) thermal spraying. By optimizing the preparation processes, a nanostructured WC-based coating with significantly improved mechanical properties and corrosion resistance to molten zinc has been obtained as compared to conventional coatings.