Microstructure and Wear Properties of Micro Arc Oxidation Ceramic Coatings

Abstract

The interaction effect of micro arc oxidation (MAO) parameters on the microstructure and wear properties was investigated. The results showed that the electric current and oxidation time significantly influenced the thickness and grinding crack width of the ceramic coatings within the range of the selected parameters, and the interaction effect of the electrical parameters was not obvious. The surface morphology, cross-section morphology, and element distribution of the coatings were observed using scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD). The results showed that ceramic coatings with γ-Al2O3 and α-Al2O3 formed, which enhanced the coating performance. After that, the microhardness and wear resistance were tested. Under the optimal process, the microhardness of a coating section was up to 1200 HV0.1, and the friction coefficient was just 0.3. When wear occurred, the volcanic microstructures experienced extrusion and deformation, and then peeled off under shear stress, which led to the formation of a grinding crack. The main failure modes of the micro arc oxidation coatings were abrasive wear and spalling failure.

Lifting Lightweight Metals to a New Level—Tribological Improvement by Hybrid Surface Solutions on Aluminium and Magnesium

“…EDS results indicate, that after the sliding tests Al 2 O 3 -phases appear as higher islands, which are smoothed within the sliding process, and a thin iron oxide layer (around 1 µm) forms on the plateaus (see results in Figure 6). The wear tracks are mainly abrasive grinding tracks of the steel ball, as was observed by Qi et al [14]. Interpreting the resulting roughness values after the sliding traces in Figure 1a, the roughness peaks of the coating decrease, while the value of the valley depth stays constant.…”

“…The plasma electrolytical oxidation (PEO) process is an advanced surface treatment, whereas the process is dominated by plasma discharges on the substrate's surface due to the high electrical voltage applied in the electrolytical process [12]. The resulting coating represents a hard and dense ceramic surface on lightweight alloys [13] which is commonly known to increase wear performance [14] on Al [15][16][17] and Mg [18][19][20][21][22] alloys. Furthermore, the PEO coating shows high corrosion protection performance [23,24], accompanied by good thermal barrier properties [25] with a high adherence to the substrate due to atomic bonding.…”

Investigation of the properties of oxide coatings on titanium alloys obtained by plasma electrolytic oxidation

“…This method allows you to change the surface condition of valve metals significantly, which makes it possible to replace traditional materials with inexpensive and nonscarce materials. At the same time, there is a significant improvement in the operational properties of products [ [8], [9], [10]].…”

Microstructure and biological activity of silicon‐doped composite coatings fabricated by micro‐arc oxidation on magnesium alloy

“…In addition, depending on the selected electrolyte, different ions can be introduced into the surface of the substrate to modify it. Compared with other surface modification techniques, it has many advantages: It can be performed without complex pretreatment of the substrate surface and requires a weak alkaline electrolyte solution; also, no harmful substances are introduced during operation, and it does not generate any harmful gas 11 . Further, it does not require special cooling equipment to realize a thick oxide ceramic layer.…”

“…Compared with other surface modification techniques, it has many advantages: It can be performed without complex pretreatment of the substrate surface and requires a weak alkaline electrolyte solution; also, no harmful substances are introduced during operation, and it does not generate any harmful gas. 11 Further, it does not require special cooling equipment to realize a thick oxide ceramic layer. Moreover, the resultant oxide coating has good corrosion resistance, wear resistance, toughness, and biomedical properties.…”