Sintering behavior of metallic and ceramic powders during pulsed electric-current sintering process

Abstract

This chapter discusses the sintering behavior of metallic and ceramic powders during pulsed electric-current sintering (PECS) process. In order to clarify the difference in sintering behavior between electrically conductive powder and nonconductive one during PECS process, densification kinetics and interparticle strength in sintered layer have been compared among PECS, direct electric-current sintering (DECS) and hot-pressed sintering (HP). Oxide dispersion strengthened (ODS) alloy and alumina ceramic powders are used as electrically conductive powder and nonconductive one, respectively. Sintering temperature, holding time and applied stress are varied in sintering. Interparticle strength is evaluated by the elevated temperature tensile testing (for ODS alloy) and Vickers indentation testing. The densification rates in sintered layer are decreased in the order of PECS<DECS<HP when ODS alloy power is used. They are comparable with each other during any sintering processes in case of alumina ceramic powder. The interparticle strength in sintered layer of ODS alloy is increased in the order of PECS>DECS>HE while there is no clear difference in that of alumina ceramic. The rapid densification and the superior interparticle strength during PECS of electrically conductive powder are mainly attributed to the amelioration of the adhesion strength of prior particle boundary due to the local heat generation by concentration of pulsed electric-current at the necked region.