Effect of processing parameters on structural features of tungsten carbide after electrical discharge machining (EDM)

Tungsten carbide (WC) is an extremely hard material which is used extensively in the manufacturing of tools and dies. In the presence of cobalt as a binder its machining becomes a difficult task because of interfacial bonding. In the EDM process, where electrical energy is used for the machining of the substance, the heat generated due to the plasma is responsible for removal of the substance at the interface. The heat generated is conducted differentially because of the composite structure of the tungsten carbide cermet. In order to improve the technological performance it is essential to understand the morphological features of tungsten carbide after machining. The studies have been conducted using different machining parameters. The objective of this study is to analyse the impact of machining parameters on the morphology of tungsten carbide suitable to withstand impact load on press forging for small components during operation. Experiments have been performed with the specially designed fixtures with proper flushing arrangements, to avoid arcing during the process. WC of P20 grade which is one of the most suitable grade substances to withstand load after EDM, has been used as work piece material for the entire study. Copper, graphite and copper tungsten electrodes have been used for the present study. The morphological features were studied with the help of the scanning electron microscope (SEM). It was observed that structural features varied with variation in electrode under similar experimental conditions. Phenomenon of such structures is discussed at length. The formations of cracks on WC have also been studied in detail. The detail of this study is presented in the paper.