Tribo-mechanical properties of thin boron coatings deposited on polished cobalt alloy surfaces for orthopedic applications

• Published in: Thin solid films Vol. 516; no. 10; pp. 3070 - 3080
• Main Authors: Klepper, C.C., Williams, J.M., Truhan, J.J., Qu, J., Riester, L., Hazelton, R.C., Moschella, J.J., Blau, P.J., Anderson, J.P., Popoola, O.O., Keitz, M.D.
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier B.V 31-03-2008; Elsevier Science
• Subjects: Amorphous materials; Biomaterials; Boron; Coatings; Cobalt alloy; Condensed matter: structure, mechanical and thermal properties; Deposition process; Exact sciences and technology; Mechanical and acoustical properties; Physical properties of thin films, nonelectronic; Physics; Rutherford backscattering spectroscopy; Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties); Tribology; Boron; Rutherford backscattering spectroscopy; Cobalt alloy; Amorphous materials; Coatings; Biomaterials; Deposition process; Tribology; Scratching test; Polyethylenes; Amorphous material; Pin on disk machine; Chromium alloys; Thin films; Biomedical materials; Steels; RBS; Orthopedic treatment; Nanoindentation; Mechanical properties; Polymer films; Adhesion; Interfaces; Vacuum techniques; Acoustic microscopy; Wear; Molybdenum alloys; Profilometry; Cobalt alloys
• ISSN: 0040-6090; 1879-2731
• DOI: 10.1016/j.tsf.2007.10.111

This paper presents experimental evidence that thin (<
∼
200 nm) boron coatings, deposited with a (vacuum) cathodic arc technique on pre-polished Co–Cr–Mo surfaces, could potentially extend the life of metal-on-polymer orthopedic devices using cast Co–Cr–Mo alloy for the metal component. The primary tribological test used a linear, reciprocating pin-on-disc arrangement, with pins made of ultra-high molecular weight polyethylene. The disks were cast Co–Cr–Mo samples that were metallographically polished and then coated with boron at a substrate bias of 500 V and at about 100 °C. The wear tests were carried out in a saline solution to simulate the biological environment. The improvements were manifested by the absence of a detectable wear track scar on the coated metal component, while significant polymer transfer film was detected on the uncoated (control) samples tested under the same conditions. The polymer transfer track was characterized with both profilometry and Rutherford backscattering spectroscopy. Mechanical characterization of the thin films included nano-indentation, as well as additional pin-on-disk tests with a steel ball to demonstrate adhesion, using ultra-high frequency acoustic microscopy to probe for any void occurrence at the coating–substrate interface.