Tribological and mechanical properties of Cu/Ni-microdiamond bilayers on brass substrates coated by composite electrodeposition technology

Currently thin-plate glass used in portable devices is initially segmented by laser beam. The material melts and vaporizes during the process, which requires micro-tools for further edge milling. Due to the poor wear resistance and short life of the micro-milling tools and the fragile nature of the glass, the processing cost is high due to the low yield. In this study, a new alternative for preparing micron diamond milling tools was reported. Bilayers on brass substrates by a composite electrodeposition technique was prepared by using diamonds with a diameter of 2-4 mu m. In order to improve the adhesion between the coating and the substrate, the electroplated pure copper was coated as the bottom layer, then the nickel and the diamond were compositely electrodeposited. The effects of current density, stirring speed, and diamond concentration in the electrolyte on the mechanical properties of the coating were investigated. The content and distribution of the incorporated diamond were analyzed by electron microscopy. It was found that, with the increase of current density, stirring speed, and the concentration of diamond in the electrolyte, the diamond content of the coating increased first and then decreased. When the parameters were: 200 rpm, 1.33 A dm(-2), 10 g l(-1), the content of the incorporated diamond in the coating became the densest and most uniform one, which enhanced the hardness and the wear resistance of the coating and reduced the roughness of the workpiece. The result of the wear test indicated that no coating composition was transferred to the glass ball, which meant the coating did not contaminate the glass material. The unique press-in mechanism protected the pull-off of the diamond and prolonged the tool's service life. The rebounding mechanism of the coating was also feasible to the machining process of the glass, which could avoid the fragment of the thin glass. The use of the composite electrodeposition technique can remarkly reduce the manufacture cost of the micro-milling tool and, in the mean time, improve the machininng efficency and quality of hard and fragile materials.