Effect of reinforcing particles on the wear rate of low-pressure cold-sprayed WC-based MMC coatings

Abstract

Tungsten carbide (WC)-based metal matrix composite (MMC) coatings fabricated using a low-cost, low-pressure cold spray unit were subjected to ASTM standard G65 dry abrasion wear testing. A linear relationship was observed between the wear rate and hardness of the various MMC coatings. Rule of mixtures (ROM) and a modified wear theory was used to explain the wear rate and material removal from the various WC-based MMC coatings. In general, the MMC coatings had wear rates closer to the values predicted by the modified wear theory. Although the MMC coatings had low wear rates close to values predicted by the equal wear theory, the cross-sectional images of the worn coatings suggested that material removal may have occurred by mechanisms governed by the equal pressure theory, where portions of, or even, the entire reinforcing particle were removed with the nickel matrix. The mean free path between the WC-based reinforcing particles was used to explain the improvements in wear rate as a function of increasing WC content in the coating. The coatings with the highest WC content and lower mean free path between the reinforcing particles had the lowest wear rates that were comparable to high-velocity oxy-fuel (HVOF)-sprayed and high-pressure cold-sprayed WC-based coatings.