The Tribological Behavior of Nanocrystalline TiO₂ Coating Produced by Plasma Electrolytic Oxidation

Abstract

Nanocrystalline TiO2 coatings were produced on titanium substrates using the plasma electrolytic oxidation technique. The effects of frequency, duty cycle, and type of applied current (pulse and direct) were evaluated on the microstructure of the coatings and the tribological behavior of the samples. Morphological evaluations demonstrated that the pancake structure was developed from coatings created with a unipolar pulsed current. However, a volcano-like surface morphology resulted from a constant current. The XRD analysis results showed that the coatings were composed mainly of the rutile phase by 77.80-96.34 wt. %. In comparison, 22.20 wt. % of the anatase phase was identified in samples produced with direct current. These phases were determined to be nanocrystalline (29.5-48.3 nm), which led to significant improvements in the tribological properties. The sample produced with direct current had larger pores, greater roughness, and a four-times higher thickness than samples created with unipolar current. Furthermore, the tribological study results showed that wear resistance was significantly higher in the unipolar pulsed current coatings than in those obtained with direct current. Moreover, samples made at a higher frequency and lower duty cycle showed better tribological behavior.

Effects of Er2(SO4)3 doping on characteristics of MAO coating

“…This was because the addition of Er 2 (SO 4 ) 3 enhanced the densification of the coating and increased the content of hard phases in it, particularly rutile TiO 2 with a higher microhardness, which was crucial for enhancing the coating's ability for resistance to wear. [29][30][31] In addition, the porous structure of the MAO coating can play a certain buffering effect on the friction to improve the wear resistance of the samples.…”

Corrosion and Wear Behavior of TiO2/TiN Duplex Coatings on Titanium by Plasma Electrolytic Oxidation and Gas Nitriding

“…The X-ray diffraction pattern of the TiO 2 sample, which PEO forms on the Titanium substrate, consists of 97.5% tetragonal crystalline rutile titanium oxide. The weight percentages of the oxides were obtained from the peak intensity in the XRD patterns and calculated by Equations (1) and (2) [ 27 , 28 ]. …”

Evaluating the Performance of Hollow Core Slabs (HCS)-Concrete and Simplifying Their Implementation

“…Note that the panel width must be greater than the beam thickness at this stage. This allows for easy placement of secondary beam blocks and forms perpendicular to the panel [32,33].…”