SINTERING BEHAVIOR OF METALLIC AND CERAMIC POWDERS DURING PULSED ELECTRIC-CURRENT SINTERING PROCESS

摘要

In order to clarify the difference in sintering behavior between electrically conductive powder and nonconductive one during pulsed electric-current sintering (PECS) process, densification kinetics and interparticle strength (binding properties between sintered particles) 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 were used as electrically conductive powder and non-conductive one, respectively. Sintering temperature, holding time and applied stress were varied in sintering. Interparticle strength was evaluated by the elevated temperature tensile testing (for ODS alloy) and Vickers indentation testing (for alumina ceramic). The densification rates in sintered layer were decreased in the order of PECS < DECS < HP when ODS alloy power was used, however, there were almost comparable each other during any sintering processes in case of alumina ceramic powder. The interparticle strength in sintered layer of ODS alloy was increased in the order of PECS > DECS > HP, while there was no clear difference in that of alumina ceramic. The rapid densification and the superior interparticle strength during PECS of electrically conductive powder were 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.