Microstructure And Property Of Flame Sprayed And Welded/PVD Ni60(WC)/CrN Multylayer Caotings

In this article, Oxygen-acetylene flame spray welding and multi-arc ion plating(PVD) technique was used to prepare CrN/Ni60(WC) multilayer coatings which have excellence wear resistance and corrosion resistance properties. The multilayer coatings are mainly used in the surface of ball valves which always surfering complex working conditions. The results show that: CrN/Ni60(WC)multilayer coatings prepared by oxygen-acetylene flame sprayed and welded and multi-arc ion plating(PVD) technique exhibit excellent corrosion resistance and wear resistance property and can equip on ball valves.Oxygen-acetylene flame sprayed and welded and multi-arc ion plating(PVD)technique was used to prepare Ni60(WC) composite coatings and CrN/Ni60(WC)multilayer coatings on 45 steel and the percentage of tungsten carbide(WC) particles are 0wt.%, 10 wt.%, 20 wt.%, 30 wt.% and 40 wt.%, respectively. Opticle microscope(OM),Scanning electron microscope(SEM), Energy dispersive X-ray detector(EDS),X-Ray Diffraction(XRD) were used to investigate surface morphology, organization structure,phase composition of the coatings. Vickers hardness tester was used to test the hardness of the surface and cross-section of the coatings. Electrochemical workstation was used to test corrosion resistance property of the coatings. The results show that:(1)Thanks to intermediate phase, like Fe Ni3, Cr B, BFe, Ni, Cr1.2Ni2.88, formed by Si, Cr, Fe, Ni and B, the Ni60 coatings exhibited high hardness; The main wear mechanism of Ni60 coatings are abrasive wear under low load and adhesive wear under high load;(2)WC particles increased the hardness of Ni60 coating. Furthermore, the hardness of Ni60(WC) composite coatings increased with increasing WC content; WC particles can increase corrosion resistance of Ni60 coatings obviously, the corrosion resistance of Ni60(WC) composite coatings increased with increasing WC content,but thep increased porosity decreased corrosion resistance;(3)While, a few molten drops and pits can be observed, the CrN film is compact and combined closely with Ni60(WC) composite coating, CrN and Cr can be observed from XRD chart and preferred orientation crystal face is(200); CrN films exhibit high hardness and increased with increasing WC content.Thanks to antifriction performance of CrN films, the friction coefficient of CrN/Ni60(WC) multilayer coating decreased and adhesive wear and abrasive wear prevented, the main wearmechanism of the multilayer coatings are slightly fatigue wear; The corrosion resistance of CrN films are excellent increased with increasing WC content, but too much WC particle can increase the porosity which will decreased the corrosion resistance of the coatings;(4)Thanks to high hardness of WC particles,the hardness of Ni60(WC) composite coatings are higher than Ni60 coatings, CrN films increased the hardness of Ni60(WC)coatings further; The WC particles supported the load, decreaed the wear degree obviously. Due to low friction coefficient of CrN films, the wear degree of CrN/Ni60(WC) multilayer coatings decreased; Due to the protection of Co, the corrsion resistance of Ni60(WC) composite coatings are better than Ni60 coatings.Due to excellence corrsion resistance of CrN films, the CrN/Ni60(WC) multilayer coatings exhibit the best corrosion resisitance property.