MANUFACTURING NANOCOMPOSITE COATINGS AND WEAR EVALUATION IN CERMETS

This work investigates the wear rate of a cermet from a NiCr alloy that is added at 5 wt% to cobalt carbide. This carbide was milled for 3, 6 and 12 hours in a high energy mill to obtain different sizes of nanometer-scale crystallites, and high velocity oxygen fuel thermal spraying (HVOF) was used to deposit the coating onto a metal substrate. The feedstocks used to obtain the coating were characterized via morphology through scanning electron microscopy (SEM), crystallite size, and crystalline phases by X-ray diffraction (XRD) as well as particle size analysis. The coatings were evaluated for microstructure (optical microscope), Vickers hardness and thickness, and wear was performed by means of solid particle erosion and Ball-on-disc tests. The results showed that the crystallite size of WCCo significantly decreased in the first milling hours. The coatings milled for 3 hours and 12 hours showed a mass loss for the erosive test of approximately 50% less than the commercial coating at the 30° angle. For erosion, at 90° angle, the coating with lower mass loss was the compound milled for 3h. All cobalt carbide compositions displayed an improved behavior relative to that of samples made from the commercial feedstock.