Material extrusion: A promising tool for processing CoCrMo alloy with excellent wear resistance for biomedical applications

CoCrMo is a prevalent alloy in prosthesis manufacturing, characterized by its favorable biocompatibility, high resistance to corrosion and high wear-resistance. Material Extrusion (MEX) Additive Manufacturing allows control over microstructural homogeneity, minimizing material waste and enabling the selection of the geometry and size of the parts, key features in the biomedical field. Granule-based MEX has been recently developed and uses a granulated metal-polymer composite as starting material that is extruded to fabricate complex parts. The binder is eliminated and the final part is obtained after sintering. This research aims to investigate the potential of MEX as a promising route for fabricating CoCrMo parts for prosthesis manufacturing. A feedstock based on Paraffin Wax and High-Density Polyethylene as binder, was prepared with optimized solid loading, then screw based MEX printing parameters, in terms of printing temperature and extrusion flow, were explored to maximize density after sintering. The microstructure development was evaluated based on carbon content, shrinkage, density, grain size, and hardness and wear performance of the optimized samples investigated. Almost fully dense parts with a microstructure free of carbides and secondary phases has been developed, which enables an excellent wear response in terms of wear rate and wear coefficient.