Influence of Al2O3 addition on the wear and corrosion behaviour of HVOF sprayed WC-12Co coatings

WC-12Co and 30wt.% of Al2O3 powder mixture was sprayed on EN-24 steel using high velocity oxy fuel (HVOF) method. The chemical, mechanical and tribological performances of WC-12Co and WC-12Co-Al2O3 coatings have been evaluated. XRD analysis clearly showed the presence of WC, Co and Al2O3 peaks in WC-12Co-Al2O3 coating. The FESEM studies showed a homogeneous microstructure with low amount of porosity in WC-12Co-Al2O3 samples as compared to WC-12Co coatings. )A, Rp=406 ) as compared to WC-12Co (Icorr=0.9A, Rp= 2010An improved hardness of 1100 Hv was observed with the addition of Al2O3 content compared to 950 Hv (WC-12 Co). The 3D roughness profiles show a higher roughness of Ra ~ 7.6µm for Al2O3 incorporated coatings when compared to WC-12Co coating (Ra ~ 6.5µm). Dry sliding wear results of WC-12Co-Al2O3 coating exhibited higher wear resistance as compared to WC-12Co coating. This is probably due to low porosity levels and good metallurgical bonding between the EN24 substrate and the coating. Electrochemical impedance spectroscopy (EIS) studies showed better corrosion resistance for WC-12Co-Al2O3 coatings (Icorr=0.1 coating. It is concluded that WC-12Co-Al2O3 coating exhibited better chemical, mechanical and tribological properties compared to WC-12Co coating under identical HVOF coating conditions.