Behavior of debinding and sintering in micron and submicron-sized copper powder injection molded parts

This study aims to reveal the behavior of debinding and sintering in metal powder injection molding (MIM) process using copper powders with varied particle sizes. The feedstock composed of micron- and submicron-sized copper powders and polyacetal-based binder was adequately prepared. Oxidation process was added between debinding and sintering steps for decarburizing. The effects of processing temperature in debinding, oxidation and sintering were evaluated from the changes in weight, dimension, and residual carbon and oxygen contents in addition to microstructure. From the results obtained using micron- and submicron-sized copper powders, it was clarified that the oxidation conditions was very important for stably-obtaining the high dense sintered parts with lower carbon and oxidation contents. This is considered to be due to the mechanism that the binder was removed from green compacts at 873K in vacuum, and then copper oxide whiskers form on the surface of copper powder and grow to connect the particles each other by oxidizing in air. The experimental result showed that using submicron-sized powder could obtain the sufficient high dense sintered parts under low sintering temperature (973K). © 2013 The Japan Society of Mechanical Engineers.