Fabrication and simulation of feedstock for titanium-powder injection-molding cortical-bone screws

Abstract

Titanium-powder injection molding is a combination of plastic injection and powder metallurgy. Using this technology, near-net titanium parts are produced. In this study, feedstock-development experiments were performed with Ti-6Al-4V powders and binders for the production of titanium cortical-bone screws. Critical solid-loading and optimum solid-loading values were determined to specify the most appropriate binder system and ratio by volume. The critical solid-loading rate was determined as 62 % by volume while the optimum solid-loading rate was 60 % by volume. The rheological properties of the feedstocks were obtained with a capillary rheometer, and the thermal properties with a TGA analysis. The rheological behavior and thermal properties of PW/PE/SA and PEG8000/PP/SA feedstocks at different mixing ratios were determined. A simulation of the flow was made with the Moldflow program, designing a screw and a mold. For the two different feedstocks, skeletal binders PP and PE were identified and simulations were carried out. The knowledge that the feedstock skeletal-binder properties predominate was obtained as the data for the flow in the mold in the light. Experiments and simulations showed that the water-based feedstock is a suitable binder system for the cortical-bone screw molding.