Comparison of the mechanical and electrochemical properties of WC-17 and 12Co coatings onto Al7075-T6 obtained by high velocity oxy-fuel and cold gas spraying

Abstract

Cold Gas Spray (CGS) coatings were produced by spraying WC-17 and 12Co cermet powders with submicronic WC particles onto aluminum alloy (Al7075-T6) substrates. WC–Co cermets have been used for wear-resistant parts due to their combination of mechanical, physical and chemical properties. Conventionally WC–Co cermets are produced by other thermal spray techniques, i.e. High-Velocity Oxy-Fuel (HVOF). A study was made to compare the mechanical and electrochemical properties of WC-17 and 12Co coatings sprayed both by CGS and HVOF obtained in this work. It is known that with a decrease in cobalt content some mechanical properties, i.e., hardness and wear resistance, are increased while others such as fracture toughness suffer the opposite effect. XRD tests were run on the powder and coatings to determine possible phase changes during the spraying process. The abrasive wear resistance and adhesive wear resistance of both optimum coatings obtained by CGS and HVOF were measured and compared in this work. The corrosion resistance was determined by electrochemical measurements. CGS for obtaining WC-17 and 12Co coatings has been proven to be very competitive when compared to coatings deposited by HVOF, obtaining dense and hard coatings onto Al7075-T6 substrates with enhanced mechanical and electrochemical properties as those produced by HVOF.