Study On High Temperature Properties And Application Of Electrical Brush Plating Ni-W Coating

In this paper the surface strengthening of the die and mould are studied by brush electro-plating Ni-W coating. On the base of parameters optimization of the electric brushing coating, Ni-W alloy coating with well-capability is obtained successfully. X-ray diffraction method (XRD),Scanning electron microscopy (SEM), NEPHOT-32 optical microscopy and HX-71 microhard tester were used to investigate the microstructure, hardness and morphology of Ni-W alloy coating both at ambient and elevated temperatures, as well as the adhesion strength between the coating and the substrate by WS-92 acoustic emission scratch tester.The high temperature oxidation behaviors and friction and wear characterization of the coating were well studied, and oxidation mechanism and friction and wear mechanism were discussed. In this experiment the conclusions given hereinafter are obtained :1. Ni-W alloy coating is a admixture of crystal and amorphous at ambient temperature. It finishes the change to crystal, gains maximum hardness with the precipitation of new particle.2. The adhesion strength between the coating and the matrix have amaximum at 700℃ treatment temperature.3. Ni-W alloy coating begins to be oxidated at 500℃, generates the ellipsoid oxidation film at 600℃. It badly destroys Ni-W alloy coating.4. Ni-W alloy coating forms the dense NiO film under 600℃. It enhances theanti- oxidation performance of the matrix.5. The wear resistant property of coating is better than that of the T10 steel and Crl2MoV steel. It is 3.3 times than T10; and 2.9 times than Crl2MoV steel. The predominant wear mechanism of the coating was determined to be the abrasive wear for T10 steel; however the adhesion wear for Crl2MoV steel.6. Ni-W coating improved the adhesion strength of coating and substrate So that Ni-W coating could improve the thermal fatigue resistance of 45 steel and 3Cr2W8V steel.7. When thermal cycle temperature changed from 500℃ to 700℃, thermalfatigue resistance would get worse.8. The result indicated that Ni-W alloy coating on automobile rod die increases the serving life 50%; and two times improvements of the serving life on wheel moulding die.