Micro-powder injection molding of cemented tungsten carbide: feedstock preparation and properties

Micro-powder injection molding (μPIM) is an advanced net-shaping process for manufacturing metal, ceramic and carbide complex micro-components. The hardmetal ceramic-metal composite cemented tungsten carbide (WC-Co) is known for its high hardness, reasonable toughness, and high abrasion and wear resistance in various applications. This study focused on the characterization and evaluation of WC-Co powder as a feedstock through μPIM. A WC-10 wt.% Co powder was mixed with a paraffin wax (PW) and low density polyethylene (LDPE) binder to obtain the feedstock. The powder-binder mixture was prepared in 49-51 vol.% powder loadings to investigate the effects of the powder content on the feedstock properties. Differential scanning calorimetry and thermogravimetric analysis were conducted to determine the mixing, injection molding, and de-molding stage temperatures. The flow behaviors of the feedstock were evaluated using a capillary rheometer. Finally, the mechanical properties and density of the molded and sintered components were evaluated. This experimental work reveals that the as-received WC powder requires de-agglomeration using sufficient ball milling to achieve an acceptable level of powder loading. The green parts were successfully molded using feedstocks with 49 and 50 vol.% powder loadings. The results indicate that the WC-10 wt.% Co feedstock with a 50 vol.% powder loading provides a sufficient compromise between moldability, green density and stiffness. After debinding and sintering, the findings indicate that a micro part can be successfully fabricated through the μPIM process using the WC-10 wt.% Co feedstock.