Comparative study of WC-cermet coatings sprayed via the HVOF and the HVAF process

摘要

The high velocity air fuel (HVAF) system is a high-velocity combustion process that uses compressedair and kerosene for combustion. Two WC-cermet powders were sprayed by the HVAF and thehigh-velocity oxyfuel (HVOF) processes, using an AeroSpray gun (Browning Thermal Systems Inc.,Enfield, New Hampshire) and a CDS-100 gun (Sulzer Plasma Technik, Wohlen, Switzerland)respectively. Several techniques, including x-ray diffraction, scanning electron microscopy, andenergy dispersive spectroscopy, were used to characterize the microstructures and phase distributionof the powders and coatings. In addition, mechanical properties such as hardness and wear resistance(pin-on-disk) were investigated. A substantial amount of W{sub}2C was found in the HVOF coatings,as well as a high concentration of tungsten in the binder phase, indicating that oxidation anddissolution processes change the composition and microstructure from powder to coating duringspraying. This was in contrast to the HVAF coatings in which composition and microstructure wereunchanged from that of the powder. Additionally, the wear resistance of the HVAF coatings wassuperior to that of the HVOF coatings.