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

J Biomed Mater Res B Appl Biomater. 2009 May;89(2):527-35. 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.

Publication types

  • Evaluation Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Carbon / chemistry*
  • Chromium Alloys / chemistry
  • Coated Materials, Biocompatible / chemistry*
  • Cobalt / chemistry
  • Diamond / chemistry*
  • Hardness
  • Hip Prosthesis*
  • Humans
  • Magnesium Oxide / chemistry
  • Materials Testing
  • Prosthesis Failure
  • Stress, Mechanical
  • Surface Properties
  • Zirconium / chemistry


  • Chromium Alloys
  • Coated Materials, Biocompatible
  • Magnesium Oxide
  • Cobalt
  • Carbon
  • Diamond
  • Zirconium
  • zirconium oxide