Wetting Behavior of Wear-Resistant WC-Co-Cr Cermet Coatings Produced by HVOF: The Role of Chemical Composition and Surface Roughness

Abstract

Despite the existence of several methods for production of superhydrophobic coatings from various materials, their application in harsh environments is still a great challenge. In this work, WC-Co-Cr cermet coatings were prepared by means of high velocity oxy-fuel (HVOF) spraying. WC particles dispersed in Co-Cr metallic matrix allowed to form the multi-scale surface roughness and thus to achieve hydrophobicity of the coatings in the as-sprayed state. The additional surface treatment by the silicone oil rendered the coatings superhydrophobic. The WC-Co-Cr coatings were fabricated from three different powder feedstocks: coarse powder with coarse WC particles, coarse powder with ultrafine WC particles, and fine powder with ultrafine WC particles. The investigation of microstructure, phase composition, and surface topography of produced coatings was conducted to study the influence of these factors on the water contact angle and surface free energy, which were obtained by the sessile droplet method. Theoretical models were used to explain the wetting behavior of all the coatings. Finally, preliminary results of the slurry abrasion response test revealed very good robustness of hydrophobicity of the coatings and also pointed to a need for further research on surface modifications for sacrificial applications.