Enhancing the tribological performance of MAO coatings through hydrostatic extrusion of cp-Ti

This study investigates the influence of plastic deformation of commercially pure titanium (cp-Ti) substrates on the tribological performance of micro-arc oxidation (MAO) coatings. Hydrostatic extrusion (HE) was employed to refine the microstructure of cp-Ti, producing ultrafine-grained (UFG) titanium, which was compared with coarse-grained (CG) cp-Ti. Both substrates were subjected to the MAO process, and the fabricated MAO coatings were analysed through X-ray diffraction (XRD), electron microscopy techniques (SEM and TEM), energy dispersive spectrometry, atomic force microscopy (AFM), and tribological testing (hardness, scratch and wear tests). The results show that HE-treated cp-Ti substrates promoted faster and thicker MAO coating formation, with superior adhesion and tribological properties compared to CG cp-Ti. The UFG substrate led to increased hardness and wear resistance, largely due to the higher density of grain boundaries and electrical resistance of the substrate, which accelerated oxide layer growth. It has been demonstrated that plastic deformation of the substrate via HE significantly enhances the performance of MAO coatings, providing improved surface protection for biomedical applications. • MAO coatings were deposited on coarse- and ultra-fine grained cp-Ti substrates. • Plastic deformation of cp-Ti substrate significantly accelerates coating growth. • Substrate HAGB and defect density influence current density during MAO process. • MAO coating on extruded cp-Ti presents higher crystallinity and rutile content. • Better adhesion and wear resistance was proved for MAO coating on extruded cp-Ti.