Investigation on Thermal Debinding of Powder Injection Molding

Powder injection molding has been accepted as an attractive net-shape manufacturing process in fabricating complex shaped and high performance parts of metals and ceramics. Thermal debinding is a critical step in the process and it consumes a major part of the processing time. Investigation of thermal debinding provides the potential for optimization of the process to prevent the formation of defects. Thermal debinding experiments on green compacts of metal and polymer mixture were carried out. Weight loss and residual polymer distribution in the compacts were measured during thermal debinding. They directly reflected the progress of polymer removal and can be used to explain the mechanisms of mass transport. Experimental results were compared with numerical predictions based on the theoretical model proposed by the authors. Good agreements were obtained. The investigation revealed that the distribution of polymer residue is a smooth continuous function of distance. A significant phenomenon, namely enrichment of liquid polymer in the outer surface region of the compact, was predicted numerically and confirmed by experimental observations.