Rheological and sintering behaviors of nanostructured molybdenum powder

Abstract

Rheological and sintering behaviors of nanostructured molybdenum powder were investigated and compared to those of commercial molybdenum powder for powder injection molding. Prior to the fabrication of feedstock, the critical solids-loading ratio of the powders and binders was measured by a torque rheometer. The mixture ratios were 46% and 50% for nanostructured and commercial molybdenum powders, respectively. The viscosities of the feedstock decreased with increasing shear rate and temperature regardless of the particle size. The Cross-WLF model was used to predict the rheological behavior of the mixtures. The sintered density and grain size of both powders were evaluated over a temperature range of 1100 to 1500°C and a time range of 0 to 480min at 1500°C. At a sintering temperature of 1500°C and a holding time of 0min, the relative density of the nanoscale powder (95%) was higher than that of the commercial powder (88%), and near full density was reached at a hold time of 480min. These results indicate that the sinterability of molybdenum powder can be enhanced by reducing the particle size, which results in more effective consolidation compared with other sintering techniques.