Study On Preparation And Densification Of W Compact Prepared By Spark Plasma Sintering

In this study, nano scale tungsten powder was synthesized via a sol-gel method followedby a reduction of hydrogen. The reduced powder was sintered by SPS at relatively lowtemperature and very short times. The whole process includes mainly three steps.Firstly, Asraw material with ammonium metatungstate, nano tungsten trioxide powder was obtained bysol-gel method when pH was1and calcination temperature of600℃, holding time of4h. Theaverage particle size of nano tungsten trioxide powder was40nm. Nano scale tungstenpowder was synthesized by a hydrogen reduction with airflow rate of1.5m3/h. The particlesize of the nanopowder was in range of25nm to62nm with an average of46nm. The nanotungsten powder was subsequently consolidated by Spark plasma sintering(SPS) at1200°Cfor different holding times and applied pressures in order to study the densification behaviorand the tradeoff between density and grain growth. Our results show that an average grainsize of0.620μm could be maintained when sintering at a pressure of600MPa and holdingtime of5min. A sintered density as high as98%was achieved by applying the pressure of1GPa. However, the presence of an extreme high pressure led to rapid grain growth, and theaverage grain size increased to0.878μm. Extending holding time resulted in the increase ofrelative density without obvious grain growth. The densification mechanism and effect ofpressure and holding time in SPS process were discussed.