Evaluation of a variety of a-C:H coatings on PEEK for biomedical implants

When the titanium layer deposited on the PEEK substrate was biased at either − 50 V or − 100 V during the deposition of the a-C:H coatings, the a-C:H coatings were harder, stiffer and more internally stressed than the two polymer-like carbon coatings. However, the a-C:H films obtained with bias voltages of − 50 V and − 100 V suffered from adhesive fracture in pull-off testing and early delamination in tribological testing. These results were assumed to be due to a titanium oxide layer which was not properly removed prior to the deposition of the hydrogenated amorphous carbon films and to the higher residual internal stress of the a-C:H films obtained with bias voltages of − 50 V and − 100 V compared with the two polymer-like films.