Tracking the Formation and End Location of Oxides in Orthopaedic Investment Casting Running Systems

This work was an investigation into a specific defect identified during the casting of Co-Cr-Mo for human prostheses. A leading cause of such scrap is the presence of sub-surface oxides that are exposed during postcasting machining operations. Their presence on the articulating surface and possible impact on wear and fatigue characteristics of the final product results in the casting being scrapped. Researchers at Birmingham have developed an Oxide Film Entrainment Model (OFEM) tracking algorithm capable of predicting the entrainment of oxides and tracking their movement and final location within simulations performed in the CFD package Flow3D. Validation of the model has been performed using DePuy's existing tree. The number of oxides each casting contained was shown to be dependent on the location of the castings. Metallurgical evaluation of the castings supported this finding. Modifications were made to the tree to reduce possible oxide formation and entrainment events during metal filling.