Influence of Process Parameters on the Tribological Behavior of PEO Coatings on CP-Titanium 4+ Alloys for Biomedical Applications

Abstract

Wear resistant ceramic coatings were generated on novel commercially pure titanium grade 4+ alloys by the plasma electrolytic oxidation technique (PEO) in an aluminate and zirconia containing electrolyte. The coatings were obtained adopting a full regular two-level factorial design of experiments (DoE) varying the PEO process parameters current density, repetition rate and duty cycle. The generated coatings were characterized with respect to its wear resistance and mechanical properties by reciprocal ball-on-flat tests and nanoindentation measurements. Thickness, morphology and phase formation of the PEO coatings was analyzed by scanning electron microscopy (SEM/EDS) and X-ray diffraction. XRD results indicate the formation of crystalline aluminium titanate (TiAl2O5) as well as t-ZrO2 and alumina leading to an increase in hardness and wear resistance of the PEO coatings. Evaluation of the DoE’s parameter interaction shows that the main effects for generating wear resistant coatings are current density and repetition rate. In particular, the formation of mechanically stable and adhesive corundum and zirconia containing coatings with increasing current density and frequency turned out to be responsible for the improvement of the tribological properties. Overall, the PEO processing significantly improves the wear resistance of the CP titanium base alloy.

Micro-Arc Oxidation in Titanium and Its Alloys: Development and Potential of Implants

“…Relatively not hard Relatively hard [13,14] Wear resistance Relatively not wear-resistant Relatively wear-resistant [15,16] Corrosion resistance Corrosion-resistant More corrosion-resistant [12,14,17] Bioactivity Biological inert Biological activity [12,18] In this review, we aim to provide an overview of MAO applied to the preparation of coatings on Ti and its alloys for biomedical applications over the past 5 years, especially orthopedic and dental implants. This review encompasses an analysis of the factors influencing the coating preparation process, and an examination of the biological functionalities of these coatings and their applications.…”

Micro-arc oxidation (MAO) and its potential for improving the performance of titanium implants in biomedical applications

“…Additives such as K2ZrF6 and K2TiF6 in silicate electrolytes can improve the sealed microstructure, increase the hardness and improve the corrosion resistance (Yang et al, 2018). Additionally, wear-resistant ceramic coatings have been generated on novel commercially pure titanium grade 4+ alloys by MAO in an aluminate-and zirconia-containing electrolyte, increasing the hardness and wear resistance of the MAO coatings (Lederer et al, 2021). The research conducted by Xiaohui Yuan et al shows that using Na2SiO3 or MgSiF6 electrolytes in MAO treatment significantly enhances the bonding strength of titanium-ceramic interfaces.…”

“…The density, frequency, duty cycle and type of current also have a significant effect on the thickness, surface roughness, corrosion resistance and porosity of MAO coatings on Ti and its alloys (Sobolev et al, 2019;Lederer et al, 2021;Grigoriev et al, 2022;Muntean et al, 2023). For example, Grigoriev et al discovered that higher current densities increased the coating thickness and surface roughness of Ti-6Al-4V alloys (Grigoriev et al, 2022).…”

“…For example, Grigoriev et al discovered that higher current densities increased the coating thickness and surface roughness of Ti-6Al-4V alloys (Grigoriev et al, 2022). Meanwhile, increasing the current density, frequency and duty cycle results in thicker and denser coatings with better tribological properties on pure Ti surfaces (Lederer et al, 2021). Higher current pulse frequencies will produce denser and less porous coatings, resulting in improved corrosion resistance (Sobolev et al, 2019).…”

Investigation of Biocompatible PEO Coating Growth on cp-Ti with In Situ Spectroscopic Methods

“…Due to the different electric regimes, not all results are comparable. PEO of Ti can be preformed in direct current (DC) [ 30 ], pulsed unipolar DC [ 31 ], and pulsed bipolar [ 32 ] regimes; all regimes can be realized either under current [ 33 ] or voltage control [ 34 ] and the combination of the regimes, and voltage ramping is also possible [ 35 ]. However, the question of the optimal PEO process duration and methods to understand in situ whether or not the process should be stopped is still open, especially for the treatment of titanium alloys under the voltage control.…”