A study on powder mixing for high fracture toughness and wear resistance of WC–Co–Cr coatings sprayed by HVOF

The effects of mixing powders with various particle sizes on the fracture toughness and wear resistance of thermally sprayed WC–10Co–4Cr coating layers fabricated by the HVOF (High-Velocity Oxygen Fuel) process on a S45C steel substrate were investigated. In order to obtain a high fracture toughness and wear resistance, the powder size and powder mixing ratio were varied. The microstructure and chemical composition of the phases in the coatings were characterized by means of the SEM and XRD techniques. Image analysis was used for the evaluation of the porosity of the coatings. Indentations tests were carried out on the cross sections of the coatings to evaluate the hardness and fracture toughness. The wear properties of the coatings were assessed using a pin-on-disk wear tester at ambient temperature without lubrication. The mixing of a small amount of coarse powders with fine powders resulted in the highest fracture toughness and wear resistance, due to the formation of coating layers having the lowest porosity.