Microstructure and properties of tungsten carbide coatings sprayed with various high-velocity oxygen fuel spray systems

This article reports on a series of experiments with various high-velocity oxygen fuel spray systems (Jet Kote, Top Gun, Diamond Jet (DJ) Standard, DJ 2600 and 2700, JP-5000, Top Gun-K) using different WC-Co and WC-Co-Cr powd ers. The microstructure and phase composition sf powders and coatings were analyzed by optical and scanning electron microscopy and a-ray diffraction, Carbon and oxygen content of the coatings were determined to study the dec arburization and oxidation of the material during the spray process. Coatin gs were also characterized by their hardness, bond strength, abrasive wean; and corrosion resistance, The results demonstrate that the powders exhibit various degrees of phase transformation during the spray process: dependin g on type of powder, spray system, and spray parameters. Within a relativel y wide range, the extent of phase transformation has only little effect on coating properties. Therefore, coatings of high hardness and wear resistanc e can be produced with all HVOF spray systems when the proper spray powder and process parameters are chosen.