Diamond-like carbon coatings enhance scratch resistance of bearing surfaces for use in joint arthroplasty: Hard substrates outperform soft

• Published in: Journal of biomedical materials research. Part B, Applied biomaterials Applied biomaterials, 2009-05, Vol.89B (2), p.527-535
• Main Authors: Roy, Marcel E., Whiteside, Leo A., Katerberg, Brian J.
• Format: Article
• Language: English
• Subjects: carbon; Carbon - chemistry; Chromium Alloys - chemistry; Coated Materials, Biocompatible - chemistry; coating(s); Cobalt - chemistry; cobalt-chromium (alloys); Diamond - chemistry; Hardness; Hip Prosthesis; Humans; Magnesium Oxide - chemistry; Materials Testing; Prosthesis Failure; Stress, Mechanical; surface modification; Surface Properties; zirconia; Zirconium - chemistry
• ISSN: 1552-4973; 1552-4981
• DOI: 10.1002/jbm.b.31244

The purpose of this study was to test the hypotheses that diamond‐like carbon (DLC) coatings will enhance the scratch resistance of a bearing surface in joint arthroplasty, and that a hard ceramic substrate will further enhance scratch resistance by reducing plastic deformation. We tested these hypotheses by applying a hard DLC coating to medical‐grade cobalt chromium alloy (CoCr) and magnesia‐stabilized zirconia (Mg‐PSZ) femoral heads and performing scratch tests to determine the loads required to cause cohesive and adhesive fracture of the coating. Scratch tracks of DLC‐coated and noncoated heads were then scanned by optical profilometry to determine scratch depth, width, and pile‐up (raised edges), as measures of susceptibility to scratching. DLC‐coated CoCr specimens exhibited cohesive coating fracture as wedge spallation at an average load of 9.74 N, whereas DLC‐coated Mg‐PSZ exhibited cohesive fracture as arc‐tensile cracks and chipping at a significantly higher average load of 41.3 N (p < 0.0001). At adhesive coating fracture, DLC‐CoCr delaminated at an average load of 35.2 N, whereas DLC‐Mg‐PSZ fractured by recovery spallation at a significantly higher average load of 46.8 N (p < 0.05). Both DLC‐CoCr and DLC‐Mg‐PSZ specimens exhibited significantly shallower scratches and less pile‐up than did uncoated specimens (p < 0.005 and p < 0.01, respectively). However, the harder ceramic substrate of DLC‐Mg‐PSZ better resisted plastic deformation, requiring significantly higher loads for cohesive and adhesive coating fracture. These findings supported both of our hypotheses. © 2008 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2009