Tribological Properties of Hard Metal Coatings Sprayed by High Velocity Air Fuel Process

Lowering the thermal energy and increasing the kinetic energy of sprayed particles by newly developed HVAF-M3 systems, can significantly reduce material decarburization, and increases sliding wear and corrosion resistance of hard metal coatings. Two agglomerated and sintered feedstock powder chemistries, respectively WC-Co (88/12) and WC-CoCr (86/10/4), with increasing primary carbides grain size from 0.2 to 4.0 microns, have been deposited by the latest HVAF-M3 process, onto carbon steel substrates. Respective dry sliding wear behaviours and friction coefficients were evaluated via Ball-on-disk (ASTM G99-90) wear tests again Al₂O₃ counterparts, and via Pin-on-disk (ASTM G77-05) wear tests against modified Martensitic steel counterparts in both dry and lubricated conditions. Corrosion behaviours were evaluated via standard Salt Spray test and electrochemical impedance spectroscopy (EIS). Optimization of coating tribological properties are discussed regarding the suitable selection of primary carbides size for different working load applications.