Effect of sintering temperature on the mechanical and physical properties of WC-10%Co through micro-powder injection molding (μPIM)

摘要

Micro-powder injection molding (μPIM) is a net shape process that is able to mass produce the micro-components of metals, ceramics, and carbides, with intrinsic and complex shapes at lower cost compared with machining, casting and powder compaction. However, the uPIM of hardmetals, such as WC-Co is more challenging due to their high thermal conductivity and ease of agglomeration. Thus, WC-Co alloy mixed with wax-based binder feedstock was selected. The formed feedstock exhibited pseudoplastic flow and was successfully injection-molded (green part). Wax-based binder was able to retain the structure of the green part during solvent and thermal debinding without any shrinkage and collapse of structure. It was sintered at 1380 °C, 1400 °C and 1420 °C. The shrinkage of the sintered part was approximately 25-31 % compared with the brown part. In the microstructure analysis of the sintered part at 1380 °C, micro-pooling of Co and porosity were observed. An increase in the sintering temperature accelerated the melted Co distribution between the grain boundary of WC, thus increasing the eta (η) phases and the grain growth. The sintered part of WC-10%Co shrank by 25-31%. The overall mechanical properties of the sintered part increased with increasing sintering temperature. The sintered parts exhibited an average transverse rupture strength (TRS) of 2042 MPa. The average hardness measured was 1667 HV, which is higher than 1620HV (theoretical hardness of the WC alloy). The average densification achieved was approximately 96% (13.85 g cm~(-3)) of the theoretical density.