Electrical Discharge Machinable Ytterbia Samaria Co-Stabilized Zirconia Tungsten Carbide Composites

Abstract

Composite ceramics of stabilizer oxide coated ytterbia-samaria costabilized zirconia (1.5Yb1.5Sm-TZP) and 24–32 vol% of tungsten carbide as an electrically conductive dispersion were manufactured by hot pressing at 1300–1400 °C for 2 h at 60 MPa pressure. The materials were characterized with respect to microstructure, phase composition, mechanical properties and electrical discharge machinability by die sinking. Materials with a nanocomposite microstructure and a strength of up to 1700 MPa were obtained. An attractive toughness of 6–6.5 MPa√m is achieved as 40–50% of the zirconia transformed upon fracture. The materials show fair material removal rates of 1 mm³/min in die sinking. Smooth surfaces indicate a material removal mechanism dominated by melting.

Spark Plasma Sintering of Electric Discharge Machinable 1.5Yb-1.5Sm-TZP-WC Composites

“…From a scientific point of view, the observed "side-effects" are, however, much more interesting. Fortunately, a study on the same materials consolidated by hot pressing is available so that the differences between hot pressing and SPS can be analyzed [30]. In the case of the hot pressed material, strength increased slightly with WC content (1550-1700 MPa at a sintering temperature of 1400 • C) and toughness on average slightly declined with rising WC content.…”

“…The recipes and the compounding procedure of the powder mixtures are explained in detail elsewhere. The materials of this study are prepared from the remaining stock of pressing feedstock of the HP study [30]. SPS sintering was carried out in a graphite die of 40 mm diameter.…”

“…1.5Yb-1.5Sm-TZP-WC composites based on identical powder mixtures were previously manufactured by hot pressing and characterized with respect to ED-machinability mechanical and electrical properties, ED-machinability and microstructure [30]. In the present study, the exact same recipes were densified by SPS in order to check if materials with identical properties and EDM characteristics are obtained.…”