AVS 63rd International Symposium & Exhibition
    Applied Surface Science Tuesday Sessions
       Session AS-TuP

Paper AS-TuP29
Characterization of Bonding between Super-hard Ceramics and Polymer Substrate

Tuesday, November 8, 2016, 6:30 pm, Room Hall D

Session: Applied Surface Science Division Poster Session
Presenter: Ranganathan Parthasarathy, Tennessee State University
Authors: R. Parthasarathy, Tennessee State University
JB. Beam, Vanderbilt University
FEH. Hoff, Tennessee State University
A. Misra, University of Kansas
L.Z. Ouyang, Tennessee State University
CML. Lukehart, Vanderbilt University
Correspondent: Click to Email
Superhard coatings improve the durability of biomedical polymer implants due to their excellent wear resistance. We study the bond strength between Rhenium Diboride (ReB2), a superhard ceramic, and Teflon, which is widely used as an implant material in load-bearing biomedical applications. As part of a proof-of-concept study, ReB2 is coated onto Teflon using confined-plume chemical deposition at room temperature and pressure. For the coating to function effectively in load-bearing conditions, the bond strength between the polymer and the coating must well exceed in-situ stresses. Accurate local measurement of bond strength using nano-indentation is difficult owing to platelet microstructure of the ReB2; hence an experimental workflow was designed to determine the average macro-scale bond strength between Teflon substrate and ReB2 coating. The inert nature of Teflon makes conventional pull-out challenging. Therefore, we performed a)Tensile pull-out of the deposited ceramic coating based on a modified version of ASTM D4541, b) Imaging of failure surfaces using light microscopy and Scanning Electron Microscopy (SEM) c) Image segmentation to determine area of failure, and d) Calculation of average stress at pull-out. The tests reveal average bond strength of 2.5 MPa between Teflon and ReB2 for coatings deposited on an untreated Teflon surface and 4.5 MPa for those on a sanded and etched Teflon surface. The pull-out occurs in a brittle manner, with no observable yield or plastic flow. The SEM images reveal strands of Teflon on the pull-out side, indicating that the true bond strength is likely higher than the measured average. Imaging of the Teflon surface under the coating reveals that the confined-plume chemical deposition creates a laminate surface of ReB2 on the substrate, as opposed to anchored platelets. The results confirm the development of a robust and repeatable workflow for the measurement of average bond strengths of super-hard ceramic coatings on comparatively soft polymer substrates.