Effect of the HVOF Deposition Process in the Chemical Composition of Tungsten Carbide Layers with Cobalt or Nickel Binders

The production of hardened surfaces on components to increase the wear resistance is a persistent technological challenge in the surfaces engineering. High velocity oxygen fuel (HVOF) thermal spray process is used to produce coatings of high wear and/or corrosion resistance. Tungsten carbide with metallic binder is often used for this purpose. In this work, coatings of tungsten carbide with cobalt or nickel binder were produced by HVOF, process and characterized by optical and electron microscopy (SEM) tests, hardness and density tests, and X-ray diffraction analysis to verify the effect of the thermal spray deposition process in the powder used for the coating production. The HVOF process produced dense coatings with low porosity and oxidation levels and high average hardness, about 1100HV. The sprayed layer of WC-12 %Co contains intermetallics of the Co_xW_yC_z type generated during the deposition process. No intermetallic formation was evidenced between the Ni and the WC on WC-10 %Ni layer. The HVOF deposition process did not significantly deteriorate the powders used.