Influence of Process-Induced Anisotropy and Synovial Environment on Wear of EBM Built Ti6Al4V Joint Implants
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JMEPEG https://doi.org/10.1007/s11665-018-3458-8
Influence of Process-Induced Anisotropy and Synovial Environment on Wear of EBM Built Ti6Al4V Joint Implants Muhammad Qasim Riaz, Matt Caputo, Mercedes M. Ferraro, and Jae Joong Ryu (Submitted February 20, 2018; in revised form April 6, 2018) 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. Keywords
additive manufacturing, lubrication, wear
microstructure,
synovial
1. Introduction Ti6Al4V is the most attractive metallic materials for biomedical applications. Due to the superior mechanical chemical properties, its application has been expanded in biomedical implants (Ref 1). The greater wear and corrosion resistance of Ti6Al4V are suitable for load-bearing joint replacements (Ref 2-4). However, these properties of metals and alloys are significantly affected by metallurgical and microstructural modifications. Applied manufacturing process determines microstructural features and also changes mechanical and chemical properties (Ref 5, 6). Additive manufacturing (AM) is the process of making a physical product directly from a CAD (Computer Aided Drafting) model. AM technologies have rapidly advanced to manufacture aerospace and biomedical components (Ref 7-10). In spite of the limitless design freedom of AM, the inherent nature of directional solidification of AM will establish anisotropic characteristics of the implant surfaces. The surface anisotropy will significantly modify the tribological and electrochemical stability of implants. There are numerous works addressing the wear and corrosion of bearing interfaces total joint replacements (TJRs) (Ref 11). Wear and corrosion of orthopedic implants is a crucial issue and has been found to significantly limit the useful life of the implants. Wear and fretting corrosion i
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