Abstract
Plasma Electrolytic Oxidation (PEO) layers were produced on Ti-6Al-4V in different conditions, so as to assess the influence of layer structure, current mode, duty cycle and surface finishing on microstructural features and tribological behaviour. In DC regime, the double-layer structure (silicate bath followed by phosphate bath) beneficially affected wear resistance. In unipolar pulsed DC (phosphate bath), the wear resistance of single layers improved with increasing duty cycle, due to improved microstructure and adhesion: high duty cycle single layers can be considered an alternative to double-layer deposition. Surface finishing by abrasive blasting with spheroidal glass beads leads to surface roughness decrease and hence to decreased friction and improved wear resistance. The best-performing PEO layers showed promising results in the comparison with reference materials such as CoCrMo (both uncoated and (Ti,Nb)N PVD-coated) and PVD-coated Ti-6Al-4V up to 30 N normal load.
Highlights
The Ti-6Al-4V alloy is widely used for orthopaedic implants due to its lower elasticity modulus, superior specific strength, biocompatibility and enhanced corrosion resistance compared to stainless steels and Co-based alloys
In order to compensate for possible metal release and, most of all, for the unsatisfactory tribological behaviour of Ti-6Al-4V in implantable biomedical devices, Huang et al [3] proposed several surface engineering techniques: oxidation produced by either heat treatment or electrolytic anodizing is one of the most popular and the vapour-phase deposition of carbon-based films (DLC-type) and thermal spraying of hydroxyapatite have been widely investigated
Plasma Electrolytic Oxidation (PEO) layers were produced in different conditions, so as to assess the influence of (i) layer structure, (ii) current mode (DC or pulsed DC), (iii) duty cycle and (iv) surface finishing on the tribological behaviour
Summary
The Ti-6Al-4V alloy is widely used for orthopaedic implants due to its lower elasticity modulus, superior specific strength (strength/density), biocompatibility and enhanced corrosion resistance compared to stainless steels and Co-based alloys. Chen et al [1] stated that, among all metallic biomaterials, Ti alloys are the only system which can bond with bone, demonstrating intimate integration with host bone tissue. Demonstrated that Co-based alloys are affected by other limitations due to adverse stress shielding effects as well as to toxic metal ions release. In order to compensate for possible metal release and, most of all, for the unsatisfactory tribological behaviour of Ti-6Al-4V in implantable biomedical devices, Huang et al [3] proposed several surface engineering techniques: oxidation produced by either heat treatment or electrolytic anodizing is one of the most popular and the vapour-phase deposition of carbon-based films (DLC-type) and thermal spraying of hydroxyapatite have been widely investigated.
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