Injection molding of HDH titanium powder

Abstract

The optimum solids loading for hydride-dehydride (HDH) titanium powder injection molding (PIM)feedstock was determined by torque rheometry, and homogeneous feedstock was prepared utilizing a twin-shaft, co-rotating mixer The effects of solvent and thermal debinding, and vacuum sintering, on binder removal efficiency, sintered microstructures, and mechanical properties of PIM HDH titanium compacts were investigated. The optimum temperature for solvent debinding was in the range of 50 degrees C-60 degrees C at which >97 w/o of the soluble binder was extracted after a 4.0 h solvent immersion. For subsequent thermal vacuum debinding, a slow heating rate (1 degrees C/min) between 200 degrees C and 450 degrees C was beneficial in removing the remaining polymeric binders. After sintering in vacuum at 1,250 degrees C, the relative density reached 98% of the pore-free level, but a hard surface layer consisting of alpha-titanium, TiC, and trace TiO2 Was readily formed. The tensile strength and elongation of the sintered titanium were 349 MPa and 6.4%, respectively. Prolonged sintering degraded the tensile properties.