Abstract
Microarc oxidation (MAO) coatings were prepared on 2024-T4 aluminum alloy using pulsed bipolar power supply at different cathode current densities. The MAO ceramic coatings contained many crater-like micropores and a small number of microcracks. After the MAO coatings were formed, the coated samples were immersed into a water-based Polytetrafluoroethylene (PTFE) dispersion. The micropores and microcracks on the surface of the MAO coatings were filled with PTFE dispersion for preparing MAO self-lubricating composite coatings. The microstructure and properties of MAO coatings and the wear resistance of microarc oxidation self-lubricating composite coatings were analyzed by SEM, laser confocal microscope, X-ray diffractometry (XRD), Vickers hardness test, scratch test and ball-on-disc abrasive tests, respectively. The results revealed that the wear rates of the MAO coatings decreased significantly with an increase in cathode current density. Compared to the MAO coatings, the microarc oxidation self-lubricating composite coatings exhibited a lower friction coefficient and lower wear rates.
Highlights
Rich aluminum resources have already been discovered on the Earth
The microstructure and properties of Microarc oxidation (MAO) coatings and the wear resistance of microarc oxidation self-lubricating composite coatings were analyzed by scanning electron microscopy (SEM), laser confocal microscope, X-ray diffractometry (XRD), Vickers hardness test, scratch test and ball-on-disc abrasive tests, respectively
The results revealed that the wear rates of the MAO coatings decreased significantly with an increase in cathode current density
Summary
Rich aluminum resources have already been discovered on the Earth. Aluminum alloy, due to its high specific strength, low density [1], proper corrosion resistance and great workability, has received much attention and is extensively applied in aerospace and transportation systems [2]. Many aluminum alloy surface modification technologies, such as physical vapor deposition, ion beam assisted deposition, hard anodizing and thermal spraying, have been developed and employed to improve the hardness and wear resistance of aluminum alloy Most of these technologies require high temperatures and are complicated to employ. Wu [17] found that the composition, structure and physical and chemical properties of MAO coatings on the surface of Ti alloy can be extensively modified by changing the anodic and cathodic voltages. MAO ceramic coatings contained many crater-like micropores of various sizes and a small number of microcracks This creates the possibility to deposit small sized lubricants into these micropores and microcracks to form microarc oxidation self-lubricating composite coatings. The microstructure and properties of MAO coatings, and the wear resistance of the microarc oxidation self-lubricating composite coatings were investigated. The adhesion strength between the MAO coatings and substrates are analyzed
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