INTERFACE ACTIVATED SINTERING OF TUNGSTEN BY NANO-PARTICLES IN THE SPARK PLASMA SINTERING

Lots of engineering components have been produced by the powder metallurgy, espe- cially for high melting point materials such as refractory metals and ceramics. Reduction in sintering temperature and/or sintering time results in reduced energy consumption and im- proved material properties in the powder metallurgy. Tungsten is a refractory metal and it is hard to obtain a full density sintered body. Main objective of this study is to make a high density tungsten sintered body at the reduced sintering temperature. Sintering is an interfacial phenom- enon between contacting particles and it is a thermally activated process. In this regard, interface activations by both process and metallurgical aspects were considered. In the former process aspects, pulsed current directly passing through conductive particle surface makes Joule heat- ing, micro-arcing, and electro-migration which are advantageous for enhancing mass flow dur- ing sintering. In the latter, it is well-known that the sintering temperature of nano-particles can be markedly reduced by the size effect. Tungsten nano-particles were synthesized by the pulse wire explosion process and then they were blended with micro-sized tungsten particles. In such a case, it could be proved that nano-particles existing at the interfaces between micro-particles played a homogeneous sintering activator when compared with other conventional irregular micro-particles and spheroidized micro-particles.