ED-machinable Ceramics with Oxide Matrix: Influence of Particle Size and Volume Fraction of the Electrical Conductive Phase on the Mechanical and Electrical Properties and the EDM Characteristics

Structural and functional properties of ceramics can be beneficial in a variety of applications. The main drawback of ceramics is their complex and costly manufacturing cycle, in particular the final machining step. For customized parts, electrically conductive ceramics represent a cost efficient alternative to conventional ceramics since electrical discharge machining (EDM) can be applied. Ceramic composites consisting of a high content of oxide matrix and a second phase that provides electrical conductivity show promising properties in wear resistance, strength, and toughness. In this study, composites with yttria stabilized zirconia as matrix material and an electrically conductive tungsten carbide dispersion (TZP-WC) were investigated. The content of the conductive phase varied from 20 to 28 vol.-% and three different particle sizes were used. Ceramic blanks were manufactured by hot pressing and then tested with respect to mechanical and electrical properties. Wire as well as sinking EDM machining characteristics were analyzed. The necessary adaptions of the EDM processing parameters to the requirements of this specific material system were investigated. The variation of the conductive phase in the observed range caused only slight variations in mechanical properties. However, a strong impact of composition on EDM characteristics was found as the contributions of different material removal mechanisms are altered. Smaller particle sizes and higher contents of electrically conductive phase generally led to higher electrical conductivity, thereby improving the machining rate at a similar surface quality.