Pulsed Electric Current Sintering of Electrical Discharge Machinable Ceramics
Pulsed electric current sintering allows densifying most ceramics at high heating and cooling rates within very short times at elevated temperature, allowing to minimise grain growth. In order to fully explore the PECS potential, it is beneficial to flow the current through the powder compact by either using conductive powder or a powder compact that becomes conductive during densification. Although in-situ Joule heating of the powder compact allows very fast heating rates, it does not necessarily result in a homogeneous temperature distribution. The influence of the current flow on densification and the impact of electrical conductivity on the temperature distribution during PECS are illustrated. The PECS technology at present is limited to the fabrication of simple geometrical shapes. Electrical Discharge Machining (EDM) on the contrary allows production of complex shapes, providing the ceramic has a minimum electrical conductivity. Although EDM has no mechanical impact, the thermal impact is high and the EDM parameters should be carefully selected in order to optimise surface quality and component strength. During wire-EDM, the fast and rough initial cut has to be followed by a sequence of lower energy finishing cuts to optimise the surface quality. The case studies presented are B4C-TiB2 ceramics and ZrO2-based composites with electrically conductive phase addition.
Pietro VINCENZINI and Jean-François BAUMARD
J. Vleugels et al., "Pulsed Electric Current Sintering of Electrical Discharge Machinable Ceramics", Advances in Science and Technology, Vol. 62, pp. 175-184, 2010