WC-Co coatings were deposited using conventional High Velocity Oxy-Fuel Jet-Kote (HVOF-JK) and Suspension HVOF (S-HVOF) methods. Microstructural and mechanical properties along with the wear resistance of coatings were investigated. Reciprocating sliding wear tests were conducted against sintered Si 3 N 4 counter-body with a normal load of 25N and total sliding distance of 500m following ASTM G133-2 standard. Coatings were characterised by Scanning Electron Microscope (SEM), X-Ray Diffraction (XRD) and nano-Indentation techniques. HVOF-JK coating showed good retention of WC whereas S-HVOF coating showed the presence of W, W2C and amorphous/nanocrystalline phases. Nano-indentation of HVOF-JK and S-HVOF showed that the relative hardness of the HVOF-JK coating was higher but their elastic modulus was lower. The lower total wear rate was exhibited by the HVOF-JK coating. This difference in wear performance is attributed to the difference in hardness of the coatings and decarburisation of WC particles.

This work investigates the sliding wear resistance of alumina coatings deposited on stainless steel substrates by HVOF and air plasma spraying, using fine (1-5 μm) and conventional (10-45 μm) powders. Sliding wear tests were carried out using a sintered WC-Co ball as the counter-body and the wear tracks were examined to obtain a better understanding of wear mechanisms. HVOF coatings showed an order of magnitude improvement in wear resistance compared to their APS counterparts. The disparity in wear performance is correlated to differences in phase composition, porosity, hardness, and fracture toughness as revealed by SEM and XRD analysis and nanoindentation testing. The development of tribofilms and their role in wear behavior is also discussed.