Microstructure, Wear and Corrosion Resistances of Atmospheric Plasma, Detonation, High Velocity Oxy-fuel and High Velocity Air-fuel Sprayed WC-10Co-4Cr Cemented Carbide Coatings

Abstract

WC-10Co-4Cr cemented carbide coating has the advantages of superior wear property and corrosion resistance. WC-10Co-4Cr coatings were prepared on 304 stainless steel substrates by different thermal spray technologies including atmospheric plasma spraying (APS), detonation spraying (DS), high velocity oxy-fuel spraying (HVOFS), and high velocity air-fuel spraying (HVAFS), respectively. The microstructure, tribological properties and corrosion resistances of WC-10Co-4Cr coatings were systematically investigated and compared. The results showed that the Vickers hardness of cemented coatings prepared by APS, DS, HVOF, and HVAF, which were all higher than those of 304 stainless steel, were 771.4 HV, 954.2 HV, 1166.2 HV, and 1162.2 HV, respectively. The volume wear rate of 304 stainless steel was about (36.82±0.80)×10^-5 mm³/N·m. The volume wear rates of APS, DS, HVOF, and HVAF coatings, which were all lower than that of 304 stainless steel, were about (7.93±0.30)×10^-5, (1.51±0.20)×10^-5, (1.17±0.10)×10^-5, and (1.10±0.01)×10^-5 mm³/N·m, respectively. In addition, the average friction coefficients of 304 stainless steel substrate, APS coating, DS one, HVOF one and HVAF one were about (0.68±0.03), (0.56±0.02), (0.48±0.01), (0.44±0.01) and (0.43±0.01), respectively. Spalling, microcracks perpendicular to the friction direction, and grooves parallel to the friction direction can be found in the wear marks of WC-10Co-4Cr coatings. Abrasive wear and fatigue wear are the main wear mechanisms of the cemented coatings. During the wear test, the carbide particles in DS, HVOF and HVAF coatings gradually became the main body bearing the friction load. Then the wear resistance of the latter three coatings was all superior to that of APS. Moreover, HVOF and HVAF coatings have better wear performances. For corrosion resistance from high to low were HVAF coating, DS one, HVOF one and APS one, respectively. The HVAF coating demonstrated the highest corrosion potential (-0.37±0.01 V_SCE), smallest corrosion current density (1.75±0.02 μA/cm²), and largest corrosion resistance (20438.5 Ω) here. The APS coating had the poorest corrosion resistance among these four coatings.