A study on the electrochemical oxidation assisted ultra-precision machining of Tungsten Carbide superalloy

Tungsten carbide (WC) superalloy has been widely used as an excellent mold material for its high hardness, good wear resistance and corrosion resistance. However, the high hardness leads to the difficulty of optically qualified complex surfaces machining. Ultra-precision machining (UPM) technique utilizes crystalline diamond as a cutting tool, which enables the generation of optical surface in nanometer scale. Despite this, diamond cutting tool suffers both mechanical wear and chemical wear when cutting WC. In this study, an integrated method combining electrochemical oxidation and diamond cutting has been proposed. It is demonstrated that surface modification by electrochemical oxidation can drastically reduce the tool wear of the diamond tool. To improve the machining performance and its overall efficiency, the underlying mechanism based on the surface microstructures during the electrochemical assisted process has been analyzed in detail. The surface morphology and surface composition were investigated after the electrochemical exposure under various voltage and current parameters. The results present that a uniform oxide layer up to 15.89 μm can be formed. It is found the Cobalt (Co) phase has the priority to oxidize. As the reaction proceeds, WC phase is also oxidized emitting CO2 gas, making the oxide layer loose. Despite this, the surface is modified and thus the hardness of the target area can be reduced effectively, which increase diamond tool life during machining.