Comparative study of air plasma sprayed and high velocity oxy-fuel sprayed nanostructured WC-17wt% Co coatings

Nanostructured WC-17wt%Co coatings were deposited using air plasma spraying (APS) and high velocity oxy-fuel (HVOF) spraying techniques. While air plasma sprayed coatings were deposited as a function of critical plasma spray parameter (CPSP) with nitrogen as the primary plasma gas, HVOF sprayed coatings were obtained with propane as the fuel gas for different oxygen to fuel ratios. Microstructural characteristics and wear performance were evaluated for the deposited coatings with the aim to correlate microstructural and tribological characteristics of coatings. Effect of CPSP on wear performance of nanostructured coatings deposited using APS was seen to be much more significant as compared to the effect of oxygen to fuel ratio for corresponding HVOF sprayed coatings. The effect of normal load on weight loss in wear tests for nanostructured coatings deposited using APS was seen to be more prominent than that for corresponding HVOF sprayed coatings. Tungsten was found to be the dominant phase in nanostructured coatings deposited using APS, while WC is the dominant phase in corresponding HVOF sprayed coatings. Further, wear resistance of nanostructured WC-Co coatings deposited using APS was found to much smaller than that for corresponding HVOF coatings, particularly at higher contact pressures.