Impact of grain size and density on the efficiency of electrical discharge machining of 8 wt.% yttria-stabilised zirconia ceramics

The relative density of 8 wt% yttria-stabilised zirconia (8YSZ) ceramics—commonly employed as a thermal-barrier-coating material—is strongly influenced by the initial powder particle size. Differences in the grain size and density considerably affect the spark discharge stability during electrical discharge machining; this poses a key challenge in achieving high machining efficiency and surface quality. To address this problem, this study proposes a method for enhancing the discharge stability of insulation ceramics by regulating the electrode current density distribution and maintaining-voltage range. This method utilises the skin effect to analyse how the grain size and density influence the current density distribution. The material removal mechanisms for 8YSZ ceramics with different characteristics are investigated via morphological and elemental analyses of the machined surfaces and processing debris. The results show that increasing the grain size and density enhances spark discharge stability, reduces thermal shock to the machined surface, and consequently increases the spalling removal volume. Thus, a new detection and control methodology is presented for improving the spark discharge stability and efficiency of machining insulation ceramics.