Investigation and modeling of binder removal process in nano/micro bimodal powder injection molding

Nano powder injection molding is an appropriate technique for the mass production of micro components. However, the large surface area of nano powder increases the processing challenges, and as a result, nano/micro bimodal powder has been introduced into the process to reduce the problems. Although the understanding of the debinding behavior directly contributes to a fabrication of defect-free parts with a high production rate, most studies for the bimodal powder injection molding focused on the feedstock rheology and properties of sintered samples. In this study, nano powder effects on both of solvent and thermal debinding processes have been investigated with nano/micro bimodal feedstocks, and the master decomposition curve was developed. To prepare the bimodal feedstocks, premixed Fe nano/micro bimodal powders were blended with a wax-based binder system as the optimal volume ratios. Solvent and thermal debinding behaviors were analyzed by observing the weight change of the samples depending on the process time and temperature, respectively. The result indicated nano powder increased immersing time required in the solvent and the amount of the residual binder. It also narrowed the decomposition temperature range of the binder system by affecting the decomposition activation energy. From the result, the master decomposition curves of each bimodal feedstock were constructed and verified.