Microstructure and properties of HVOF-sprayed chromium alloyed WC–Co and WC–Ni coatings

In this paper the influence of the type of binder metal (nickel or cobalt) and chromium as an additional alloying element on the microstructure, mechanical properties and wear resistance of high velocity oxy-fuel (HVOF)-sprayed WC-based hardmetal coatings was studied. Plain WC–Co and WC–Ni as well as five chromium alloyed compositions were sprayed with a liquid-fueled HVOF-spray process from commercial and experimental agglomerated and sintered feedstock powders. The coating characterization included optical microscopy and SEM of metallographically prepared cross-sections, hardness measurements, determination of the Young's modulus and phase composition by X-ray diffraction. Erosion and dry oscillating sliding wear were studied. The resistance to erosive wear was found to be improved when cobalt was used as binder metal. A dependence on the chromium content was not detected. For the oscillating sliding wear against a hardmetal counterbody there is no dependence of the wear rate on the type of binder metal or the amount of chromium.