Comparison of the Mechanical and Electrochemical Properties of WC-25Co Coatings Obtained by High Velocity Oxy-fuel and Cold Gas Spraying onto Al7075-T6

摘要

Cold Gas Spray (CGS) coatings were produced by spraying WC-25Co cermet powders onto Al7075-T6 substrates. Unlike conventional thermal spray techniques, i.e. HVOF, no melting of the powder occurs, and the particles are deformed and bonded together, after being sprayed by a supersonic jet of compressed gas, to build up several layers to form a coating. WC-Co cermets have been used for wear-resistant parts due to their combination of mechanical, physical and chemical properties. XRD tests were run on the powder and coatings to determine possible phase changes during the spraying process. The bonding strength of the coatings was measured by adhesion tests; their abrasive wear resistance was also studied. The corrosion resistance was determined by electrochemical measurements. The derived mechanical and electrochemical results were compared with those obtained in this work by HVOF. Cold Gas Spraying for obtaining WC-25Co coatings has proven to be very competitive when compared to coatings deposited by conventional thermal spraying techniques, obtaining thick, dense and hard coatings onto Al7075-T6 substrates with better or equal mechanical and electrochemical properties as those produced by HVOF.