A new binder for powder injection molding titanium and other reactive metals

Abstract

This paper describes the development of a new aromatic-based binder for powder injection molding (PIM) reactive metals, such as titanium, zirconium, niobium, tungsten, and molybdenum. Detailed processing results are discussed for titanium alloy (Ti-6,4) compacts fabricated using the new binder system. Because of the choice of the binder constituents, thermal removal is readily accomplished at low temperatures and short times via vacuum sublimation. In this way the binder can be cleanly extracted from the green part prior to sintering to minimize the amount of residual carbon left in the final component. Rheological measurements indicate that powder loadings in the PIM feedstock as high as 67 vol.% could be achieved using the new binder system, while still maintaining low mixing torques and injection molding pressures. Results from chemical analyses conducted on the Ti-6,4 powder before injection molding and the Ti-6,4 compacts after final sintering demonstrate no significant increase in carbon content due to processing. The raw powder contained 210 ppm carbon, while the as-sintered, PIM formed compacts exhibited 217 ppm carbon content.