Evaluation of micromechanical behaviour of plasma electrolytic oxidation (PEO) coatings on Ti–6Al–4V

This paper investigates the micromechanical behaviour and wear properties of coatings on a Ti–6Al–4V alloy generated using the plasma electrolytic oxidation (PEO) technique. Four different compositions of electrolyte were used: aluminate, phosphate, silicate, and mixed phosphate and silicate. The coatingsʹ composition was characterised using X-ray diffraction and energy dispersive spectroscopy, and their morphologies were examined using SEM and optical interference profilometry. Following this, the micromechanical properties of the different coatings and the substrate alloy were examined using nanoindentation, nanoindentation scratch, nanoindentation impact, and modified grit blasting equipment. Correlations between these mechanical performance measures and observed structures are discussed. The aluminate-based coating, which contained a hard Al2TiO5 phase, was found to outperform other candidate systems and gave a performance enhancement over the bare substrate. However, it appears to be prone to delamination.