Characteristics and corrosion-wear response of s-phase coated ortron 90

The present work forms part of a larger investigation which has the overall aim to determine the potential of applying hard S-phase coatings to Ortron 90 to enable a long-term improvement in THR life through the mitigation of osteolyis. Hard coating materials like S-phase, a nitrogen supersaturated stainless steel, have the potential to limit the damage that accumulates on metallic femoral head components in-vivo. A range of S-phase coatings of differing nitrogen concentration [N], produced by magnetron sputter deposition, were examined. Scratch tests, using physiologically relevant loads, indicated that S-phase coatings usefully limit the heights of lips associated with scratch damage. Coatings with a low [N] were more fracture resistant than those produced with higher [N] values. Moreover, all coatings were slightly more noble than uncoated Ortron 90 when subjected to single cycle polarisation tests in physiological saline at 37 degrees C. Corrosion-wear tests, made in sliding contact with Al2O3, in physiological saline solution, showed a slight improvement in corrosion-wear resistance when Ortron 90 was coated with S-phase with a [N] of similar to 28.5 at.%. The other coatings showed a similar corrosion-wear resistance to uncoated Ortron 90. When reciprocation sliding wear tests were conducted using cathodic protection, the corrosion component of corrosion wear was eliminated. Under these conditions, mechanical wear mechanisms predominated; wear resistance increased with increasing coating hardness. These results demonstrate that under normal (open circuit potential) conditions the corrosion component of corrosion-wear plays a dominant role in the overall rate of surface degradation during sliding contact.