Effect Of Rare Earths On Plating Properties Of Electroplated Diamond Tools

Electroplated diamond tools are widely applied to the machining of hard and brittle materials. Plating is one of important elements which affect the properties of electroplated diamond tools. The pure nickel, the bright nickel and the nickel cobalt are common electroplated plating, which has behaviors of corrosion resistance and wear resistance. In order to improve the diamond tool performance and the bond strength between substrate and plating, and to obtain the machining efficiency and tool life, this article applies the rare earths to the manufacture of electroplated diamond tools. The effect of LaCl₃·7H₂O additive contents on bright nickel electrodeposits was studied in a typical nickel electroplating solution. The goal is to improve the performance of bright nickel electroplated tools, and to analyze the influence of rare earths on bright nickel plating performance. Bright nickel and nickel lanthanum plating surfaces and section specimens were prepared separately. The surfaces, cross section microscope and hardness were measured. The plating friction and wear tests were carried out on pin-disk wear tester. Bond strength between electrodeposited layer and the tool substrate were measured with digital-image correlation method. Cathode polarization curves were obtained through electrochemistry direct current polarization test system. Grinding experiments were conducted on cylindrical grinder to compare the grinding ratio of diamond tools.The rare-earth element causes small size grains of bright nickel plating. With the content of LaCl₃·7H₂O 5g/L on nicked solution, the bright nickel plating presents the smallest crystal grains and hardness of 475 HV. The be coating structure can be changed through heat treatment. Hardness of plating may improved at suitable temperature range of heat treatment. Rare earth bond strength between plating and substrate is improved with rare earth addition. Cathode polarization degrees vary with rare earth content. The diamond tools contain rare earth have the grinding ratio of 322.9. Experiment results indicated that rare earth could improve the hardness of bright nickel plating, the cathode polarization ability, the substrate bond strength and the grinding ratios of diamond tool. In addition, digital-image correlation method is applied to measure the bond strength between plating and substrate of diamond tools.