Influence of Process-Induced Anisotropy and Synovial Environment on Wear of EBM Built Ti6Al4V Joint Implants

Additive manufacturing (AM) technology is identified as an ideal solution to overcome challenges in design and manufacturing of complex components. However, the layered fashion of AM process result in directionally solidified microstructures on the system. The anisotropic surface texture will affect wear and corrosion resistance. The current study investigates tribological responses of AM-made Ti6Al4V for joint implant applications during the combined effect from synovial lubrication and process-induced surface structure on surface fatigue damage response. Electron beam melting was used to produce Ti6Al4V specimens and mechanical characterizations were performed using nanoindentation and micro bending tests to determine their mechanical properties. A series of pin-on-disk wear tests were performed to quantify sliding contact fatigue damage in three simulated synovial fluids with variable concentrations of bovine serum albumin and hyaluronic acid in the PBS solution. Physical properties of simulated synovial fluids were measured using a nanoindenter-based technique and correlated to fatigue wear response. The lower wear rate is found in greater protein concentrations. The results presented AM build direction significantly affects sliding fatigue wear resistance on TI6Al4V surface in all synovial environments.