Electrical discharge machinable (Y, Nd) co-stabilized zirconia – Niobium carbide ceramics

Electrical discharge machining (EDM) of electrically conductive ceramics offers the possibility to manufacture customized ceramic components from sintered blanks. In this study two different yttria neodymia co-stabilized TZP materials containing 28 vol% niobium carbide were manufactured by hot pressing at 1275 °C–1400 °C and axial pressure of 60 MPa and compared to a 3Y-TZP based reference. The co-stabilized ceramics offer a strength up to 1250 MPa and a hardness of 14 GPa. The fracture resistance can be tailored between 7.4–9.7 MPa√m by variation of the yttria/neodymia ratio and the sintering temperature. These composites, however, require an exact setup of machining parameters. Die sinking EDM experiments revealed that the dominant material removal mechanism is melting. Machined surfaces can achieve low roughness Ra =0.3 μm combined with material removal rates of 1.5 mm³/min. The choice of excessively high energy parameters in EDM may lead to crack formation, spallation and phase accumulation during re-solidification.