Comparative Study of the Properties of WC-Co Nanostructured and Bimodal Coatings, Sprayed by High Velocity Oxy-Fuel (HVOF)

Abstract

Abstract Over the last years, the grain size reduction to the nanometric scale has experienced an increasing interest because of its enhanced properties. This study is based on WC-Co cermet materials, which have a great application in the wear resistance materials field. In the Thermal Spray Center (CPT) of the University of Barcelona, two coatings using nanostructured and bimodal WC-Co cermet powders have been obtained by means of High Velocity Oxygen-Fuel (HVOF) technique. Both were sprayed under the same spraying parameters. Structural characterization for both feedstock materials and coatings have been performed using XRD, SEM and TEM. The friction wear resistance of the coatings has been studied by Ball-on-Disk test (ASTM G99-90), and the abrasive wear resistance has been quantified by Rubber-Wheel test (ASTM G65-91). Finally, the corrosion resistance has been studied by electrochemical techniques and a salt fog spray test. The nanostructured coating shows more hardness, but the bimodal coating shows better abrasive and friction wear resistance. Both coatings shows good corrosion resistance, better than the conventional coatings of WC-Co. The bimodal powder have the added advantage of being not as expensive as the nanostructured powder, and even providing better properties.