Study On Alumina Part Fabricated By Powder Injection Molding

The process of mixing, debinding and sintering for5μm alumina powder was investigated with four binder component consists of LDPE, EVA, PW and SA.In the mixing part, excellent feedstock could be produced with appropriate mixing equipment and proper technology. The mixing temperature of alumina powder system was set at150℃, the rotate speed was50r/min running2h. The effect of different binder ratio on the homogeneity of feedstock was also investigated, the result showed that the content of SA had a great influence on homogeneity, the alumina feedstock was best mixed with the binder proportion of WLDPE:WEVA:WPW:WSA=35:35:35:25, the powder loading could reach58vol%and showed nice rheological behavior.In the debinding part, the method of solvent debinding combined with thermal debinding was firstly tried, but the result was undesirable, the sample could be prone to defects, so the one-step thermal debinding method was adopted. In the thermal debinding stage, the effect of heating rate and dwelling time on feedstock were investigated. In the beginning of debinding, slowing the heating rate and extending the dwelling time were essential, and then the suitable process was obtained. The process was optimized:Room temperature-62℃, heating rate of4℃/min;62～164℃, heating rate of0.65℃/min, dwelling time for90min;257～363℃, heating rate of1℃/min, dwelling time for30min;363～483℃, heating rate of2℃/min, dwelling time for60min. The debinding duration was decreased to792min and the wasting of resources was avoided, the debinding ratio was99.5%.Sintering was the final step of Powder Injection Molding, it had a great influence on the densification, micro structure and dimensional accuracy of body, and it also determined the final performance of sintered materials. In the same heating rate and holding time, the effect of different sintering atmosphere and temperature on hardness and density were compared. The best sintering process was:In the atmosphere of vacuum, the sintering temperature was1500℃, heating rate of10℃/min, dwelling time for60min, then cooling with air. The color of the sintered sample was white, the body had nice densification and showed excellent mechanical property.