Investigation of Tribological Characteristics of PEO Coatings Formed on Ti6Al4V Titanium Alloy in Electrolytes with Graphene Oxide Additives

Abstract

Coatings with a thickness from ~40 to ~50 µm on Ti6Al4V titanium alloys were formed by plasma electrolytic oxidation (PEO) in a silicate-hypophosphite electrolyte with the addition of graphene oxide. The PEO treatment was carried out in the anode–cathode mode (50 Hz) at a ratio of anode and cathode currents of 1:1; their sum density was 20 A/dm2, and the treatment’s duration was 30 min. The effect of the graphene oxide’s concentration in the electrolyte on the thickness, roughness, hardness, surface morphology, structure, composition, and tribological characteristics of the PEO coatings was studied. Wear experiments, under dry conditions, were carried out in a ball-on-disk tribotester with an applied load of 5 N, a sliding speed of 0.1 m·s−1, and a sliding distance of 1000 m. According to the obtained results, the addition of graphene oxide (GO) into the base silicate-hypophosphite electrolyte leads to a slight decrease in the coefficient of friction (from 0.73 to 0.69) and a reduction in the wear rate by more than 1.5 times (from 8.04 to 5.2 mm3/N·m), with an increase in the GO’s concentration from 0 to 0.5 kg/m3, respectively. This occurs due to the formation of a GO-containing lubricating tribolayer upon contact with the coating of the counter-body in the friction pair. Delamination of the coatings during wear occurs due to contact fatigue; with an increase in the concentration of GO in the electrolyte from 0 to 0.5 kg/m3, this process slows down by more than four times.

Effect of Graphene Oxide as an Anodizing Additive for the ZK60A Magnesium Alloy: Correlating Corrosion Resistance, Surface Chemistry and Film Morphology

“…Additionally, it is more compact, being permeated by fewer pores and cracks. A possible explanation for the decrease in the anodic layer thickness with increasing GO concentration is related to the agglomeration of GO particles that reduce the growth rate of the anodic film or blocks discharge channels during the anodizing treatment, as suggested by Grigoriev et al for a PEO/GO composite coating formed on the Ti-6Al-4V alloy [38]. The main elements that constitute the anodic film are also Mg, O and Si.…”

Dental Implants: Modern Materials and Methods of Their Surface Modification

“…Plasma electrolytic treatment (e.g., Plasma electrolytic oxidation) [177,302,[353][354][355][356][357][358][359][360] Simple, inexpensive, and environmentally safe method. It allows to apply various (in particular, polymeric) coatings on metal and ceramic substrates with their simultaneous cleaning in order to increase the corrosion resistance of implants.…”

Solid Lubrication System and Its Plasma Surface Engineering: A Review

“…These free radicals undergo cross-linking and re-bond to form a network structure, thereby improving the surface performance of the material [21,22]. By using different plasma preparation techniques and solid lubrication material system components, the lubrication performance of the coating improved to meet the needs of special working conditions [23][24][25][26][27]. This article elaborates on the plasma preparation methods of lubrication coatings, introduces relevant solid lubrication coating systems, and prospects for the future development trend of solid lubrication coatings.…”