Corrosion and Wear Analysis of High-Velocity Oxy-Fuel Sprayed WC-10Co-4Cr and Colmonoy-6 Coatings on Nickel-Aluminum Bronze Alloy Substrate

Nickel-aluminum bronze (NAB) alloys are widely used in hydraulic and pumping bodies due to their suitable mechanical properties and corrosion resistance. However, the tribological performance of these materials needs to be improved. In this study, the WC-10Co-4Cr, and Colmonoy-6 coatings were applied on a NAB alloy using high-velocity oxy-fuel (HVOF) spraying technique to enhance the corrosion and wear performance of the NAB substrate. The XRD phase analysis evidenced the dominant presence of the WC and W2C phases in the WC-10Co-4Cr coating and the Ni2Cr3 and Si2B3 compounds in the Colmonoy-6 coating. Morphological and surface analysis showed the formation of the coatings with roughness values of R-a = 4.9 +/- 0.9 lm for Colmonoy-6 and R-a = 6.8 +/- 1.1 lm for WC-10Co-4Cr coatings. The electrochemical measurement in a 3.5 wt.% NaCl solution revealed that applying WC-10Co-4Cr and Colmonoy-6 HVOF coatings improved the corrosion resistance of the NAB substrate by one order of magnitude. This improvement was more significant for Colmonoy-6 coating due to the presence of electrochemically nobler compounds containing Cr and Ni. Wear measurements obtained by pin-on-disk wear test and morphological analysis of the worn path showed the lowest friction coefficient and highest wear resistance for the WC-10Co-4Cr coating followed by Colmonoy-6 coating. The superior wear performance of the WC-10Co4Cr coating was attributed to its comprehensive mechanical properties with a Vickers hardness of 1152 +/- 25 HV30, while the hardness for Colmonoy-6 and NAB substate was 789 +/- 65 and 164 +/- 5 HV30, respectively.