Study On Properties And Application Of Electrical Brush Plating Co-W Coating

In this paper, the brush electro-plating Co-W coating and its strengthening on the die and mould were studied. On the base of parameters optimization of the electric brushing coating, Co-W alloy coating with good performance was obtained successfully. By means of X-ray diffraction method (XRD), Scanning electron microscopy (SEM), NEPHOT-32 optical microscopy and HX-71 microhardness tester, the microstructure, hardness and morphology of Co-W alloy coating both at ambient and elevated temperatures were investigated. In addition, the adhesion strength between the coating and the substrate was studied using a WS-92 acoustic emission scratch tester.The high temperature oxidation behaviors and friction and wear characterization of the coating were studied. Co-W alloy coating is amorphous at ambient temperature. It transforms to crystalline structure at500℃, and obtained maximum hardness with the precipitation hardening. The adhesion strength between the coating and the matrix reaches the maximum after treatment at 700 ℃Co-W alloy coating starts to be oxidized at 500℃ with perceivable rate.Below the 600C, a dense CoO oxide was formed and effectively retarded the oxidation process. Above 600C, a layer of ellipsoid oxide film wasformed which severely damages Co-W alloy coating. On the base of the above observation, the oxidation mechanism and friction and wear mechanism were discussed.The wear resistance of the coating is much higher than that of the T10 steel and Crl2MoV steel, being 3.3 times that of T10 and 3.4 times that of Crl2MoV steel. The predominant wear mechanism of the coating was determined to be the abrasive wear for T10 steel; while the adhesion wear for Crl2MoV steel. Co-W coating improved the adhesion strength between coating and substrate, so that Co-W coating could improve the thermal fatigue resistance of 45 steel and 3Cr2W8V steel.The application of the Co-W alloy coating indicated that the coating on automobile rod die increases the service life by 1.8 times; and on the wheel moulding die by 3.2 times.