The tribological properties of bioceramic coatings produced on Ti6Al4V alloy by plasma electrolytic oxidation

In this study, hydroxyapatite and calcium apatite-based bio-ceramic composite coatings were produced on Ti6Al4V alloy by plasma electrolytic oxidation (PEO) in the electrolyte consisting of calcium acetate (CA) and β-calcium glycerophosphate (β-Ca-GP) for different treatment times. Coating thickness, phase structure, coating morphology of the cross section, elemental composition, adhesion strength, wear resistance and tribological property of the PEO coatings were analyzed by eddy current method, X-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive spectroscopy (EDX mapping), micro scratch tester and tribometer, respectively. The average thickness of the coatings varied from 28 to 52 µm with increasing times. The XRD results indicated that anatase (TiO2), rutile (TiO2), TiP2, TCP (Ca3(PO4)2), perovskite – CaTiO3 and hydroxyapatite (Ca10(PO4)6(OH)2) phases were formed on the Ti6Al4V alloy after PEO. According to the EDS mapping results, uniform Ca and P elemental distributions were observed on the surface of PEO coatings. The adhesion strengths of the PEO coatings enhanced with increasing time. The wear resistances and tribological properties of the PEO coatings were greater than those of the uncoated Ti6Al4V alloys, and they were increased with increased time.