Tribological and corrosion properties of -TiNb alloy modified by plasma electrolytic oxidation: Evaluation of the synergistic effect of composition and processing time through statistical evaluation

For bone implants, beta-titanium alloy is promising mainly due to its low modulus of elasticity; the disadvantage may be the insufficient wear-resistant and corrosion-resistant properties. Bulk beta-Ti39Nb alloy and magnetron sputtered beta-Ti39Nb alloy were surface modified by micro-arc oxidation (MAO) technique in an alkaline solution. The aim was to define in detail the relationships between the chemical composition of the surfaces, their morphology, and the tribological and corrosion properties. The structural properties, phase and chemical composition of the coating, tribological and corrosion properties were studied in detail using SEM, EDX, XRD, XPS and EDX analysis. The particles released during tribological measurements were evaluated using SEM/EDX particle analysis followed by statistical treatment of the particle parameters (material, size, area) using multiple factor analysis and principal component analysis. The results show that increased wear resistance was achieved for both magnetron-sputtered layers and bulk materials. The friction coefficient for the MAO-Al2O3 friction pair samples ranged from 0.5 to 0.6 in phosphate-buffered solution. For powder metallurgy-prepared bulk beta-Ti39Nb, MAO represents an effective tool to reduce the high friction coefficient from 1.0 to 1.1 to values of 0.4-0.5. The results of the particle analysis confirm that with increasing MAO process time, there is an increase in the number of released particles with increased Si content, which correlates well with the results of tribological tests. The evaluated tribological parameters wear rate, track width, and the chemical elements Si and Ti have a significant weak positive correlation, confirming that the presence of these elements in MAO coatings affects the resulting tribological parameters. Multivariate analysis revealed the greatest correlation of the resulting particle composition with the tribological attributes and original material and, to a lesser extent, with the process time.