TiB2 conducts the current and forms a liquid phase at the interface with BN. Neighboring crystals of BN and some TiB2 spall due to thermal shock. During pause periods parts of the liquid and fragments are flushed out by the dielectric. Composites rich in TiB2 or with fine TiB2 grains gave high material removal rates. Increasing the amount of the conducting phase by 10% is as effective as decreasing the grain size from 11 to 7 μm. Coarse TiB2 could withstand high pulse durations before wire breaks. Material removal rate increases with pulse duration, frequency, and current. For the same composition and grain size, increasing the pulse duration or current increased the crater depth (the roughness) up to a certain value, beyond which increasing these parameters yielded a smoother surface. The conductivity of the dielectric was effective only for compositions rich in TiB2 content. In such cases, higher water conductivity lowered the energy required for material removal.