Development and Application of Electrically Conductive Ceramics
Hybrid ceramics which consist of an electrically isolating matrix (Al2O3 or Si3N4) and an electrically conductive minority phase (TiN) were investigated with respect to their suitability for electrical discharge machining EDM. The influence of concentration and particle size of the minority phase on the degree of percolation and the average size of electrically non-connected volumes were studied. The calculations showed that the concentration of the conductive phase can be minimised by reducing the grain size of the conductive phase. For achieving a low surface roughness by EDM, a minimum of 90 % percolation is required. By using a nano-sized TiN powder, the sintering temperature could also be reduced by several 100 °C. This reduces production costs and helps to avoid problems due to detrimental reactions between the matrix and carbon impurities. Several demonstrators were set-up and tested which were designated for harsh working conditions.