Liquid phase sintering characteristics of tungsten powder obtained by electrochemical reduction technique

A remarkable alternative extraction process has recently been announced for tungsten powder production, which is simpler and safer than the conventional fabrication method. Even though the process has a promising commercializing potential, sintering behavior of the produced tungsten powder has not been investigated up to now. In this study, sintering behavior of the electrochemically produced tungsten powder was investigated and compared with a commercially available tungsten powder. Unalloyed and alloyed specimens, containing at least ninety weight percent commercial or produced tungsten powder, were sintered with different sintering conditions. The alloys had single additives W/X (X:Ni, Co, Fe) or different Ni/Fe, Co/Fe an Ni/Co/Fe ratios. A series of characterization techniques were performed to investigate the micro and macro scale property variations in prepared pellets. The sintered densities of the specimens were measured by Archimedes method. Microstructure investigations were conducted by optical microscope (OM) and scanning electron microscope (SEM). In addition, x-ray diffractometry (XRD), x-ray fluorescence (XRF) and energy dispersive spectroscope (EDS) analyses were applied to determine the formed intermetallics, solid solution phases as well as impurities and their ratios. The mechanical properties of the selected specimens were measured using micro and macro hardness tests. It was found that electrochemically produced tungsten powder employed heavy alloys could not densify up to expected relative density values, whereas the unalloyed ones demonstrated higher densification tendency than commercial tungsten pellets. This behavior was attributed to impurity content of the electrochemically produced tungsten. Keywords: Tungsten, electrodeoxidation, calcium, solubility effect on densification, tungsten heavy alloys, solid state sintering, liquid phase sintering.