Formation of Tungsten Carbide Coatings with Different Thermal Spray Guns

WC-12%Co powder of 53 mu m-63 mu m particle size were thermally sprayed by using high velocity oxygen fuel gun (HVOF) MicroJet and modified gas flame gun TopJet/2. Gas ratio during the spraying time was sistematically varied to define influence of spraying parameters on the quality of coatings. Adhesive strength test were carried out by pull-off the pin method using an original device. Surface morphology investigation of the WC-12%Co coatings, sprayed by the MicroJet gun and modified gas flame gun TopJet/2, showed that the increase of the fuel gas flow rate resulted in reduction of the surface roughness and porosity as well as improved sintering of the particles. Adhesive strength of the coatings sprayed by the MicroJet gun varies from 46.5 MPa to 59.7 MPa. Fuel gas flow rate increase resulted to sudden increase of the adhesive strength. The adhesive strength of coating sprayed by modified TopJet/2 gun was smaller.