Nanopowder Effect on Fe Nano/Micro-Bimodal Powder Injection Molding

The nano/micro-bimodal powder injection molding (PIM) process takes advantage of nano-PIM. Most studies of the process were performed with bimodal powder feedstocks containing only small amounts of nanoparticles because they focused on properties of the samples with the optimal contents of nanoparticles. This study presents how nanoparticles in bimodal powder affect the PIM process. Five different feedstocks were prepared with the powders containing nanoparticles from 0 to 100 pct. The result demonstrated that a decrease in solids loading was offset by nanoparticle addition due to the bimodal packing effect. The nanoparticles also increased the difficulty of the debinding process. Sintering was conducted at 1173 K (900 °C), at which the highest sintered density could be obtained, with various isothermal holding times. Unlike the density, the hardness did not reveal any dependence on the holding time due to grain growth. From this study, 25 pct was regarded as the optimal content of the nanoparticles in the bimodal powder for the maximum density and hardness.