Microstructure and Properties of High Velocity Oxy-Fuel Sprayed Micro-Nano WC-Cr3C2-CoNi Coating

For studying the deposition behaviour of dual-carbides cermet particles on coating microstructure and properties，the surface morphology and cross-sectional microstructure of the original powder and the flat particle on the low-carbide steel substrate were analyzed，and the microstructure，phase constitution and properties of HVOF sprayed micro-nano WC-Cr3C2-CoNi coating were investigated systemically.Results showed that the particles deposited on the substrate showed a caky shape with smooth and convex surface，radial sputtering streaks appeared around the particles，and the thickness of flat particles was much smaller than their radial dimensions.In addition，the section microstructure of the coating presented certain lamellar characteristics，and the interfaces between flat particles，hard phase and bond phase，flat particle and substrate and different hard phases bonded well.The coating had the main phase of WC，some decarburized phases，and the amorphous phase of Cr2O5.Moreover，the microhardness，elastic modulus，fracture toughness，adhesive strength and wear weight loss of the coating were (13.19±0.52) GPa，(145.17±3.89) GPa，(2.59±0.64) MPa·m1/2，(38.41±0.51) MPa and (6.08±0.68) mg respectively.Compared to WC-Co12 coating，the decomposition of WC and the decarburized phases decreased significantly in the HVOF sprayed micro-nano WC-Cr3C2-CoNi coating and the coating’s mechanical properties were obviously improved.