Abstract
Microarc oxidation (MAO) coatings were prepared on 2024-T4 aluminum alloys using a pulsed bipolar power supply at different anode pulse-widths. After the MAO coatings were formed, the micropores and microcracks on the surface of the MAO coatings were filled with Fluorinated ethylene propylene (FEP) dispersion for preparing MAO self-lubricating composite coatings containing FEP. The effect of the anode pulse-width on the microstructure and wear resistance of the microarc oxidation coatings was investigated. The wear resistance of the microarc oxidation self-lubricating composite coatings was analyzed. The results revealed that the MAO self-lubricating composite coatings integrated the advantages of wear resistance of the MAO ceramic coatings and a low friction coefficient of FEP. Compared to the MAO coatings, the microarc oxidation self-lubricating composite coatings exhibited a lower friction coefficient and lower wear rates.
Highlights
Aluminum alloys, due to their advantages of high strength to weight ratio, lightweight [1], proper corrosion resistance, and great workability, have received much attention and are extensively applied in various industries [2]
The porosity of the Microarc oxidation (MAO) ceramic coatings increased significantly and the MAO coatings became more porous as the anode pulse-width increased from 1000 to 4000 μs
The porosity and defects in the MAO coatings increased anode pulse-width. This increased the formation of crack sources and exfoliation during and the compactness of the MAO coatings decreased with the increase in the anode pulse-width
Summary
Due to their advantages of high strength to weight ratio, lightweight [1], proper corrosion resistance, and great workability, have received much attention and are extensively applied in various industries [2]. Many surface modification technologies have been developed and employed to improve the hardness and wear resistance of aluminum alloys Most of these technologies require high temperatures and are complicated to employ. The ceramic coatings prepared by MAO have high hardness, good adhesion to the substrate, excellent wear resistance, etc. Yin et al [24] prepared self-lubricating alumina-graphite composite coatings using a one-step PEO process in the appropriate graphite-dispersed electrolyte solution This MAO composite coating showed excellent performance. MAO ceramic coatings typically contain 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 the MAO coatings, and the wear resistance of the microarc oxidation self-lubricating composite coatings were investigated. The adhesion strength between the MAO coatings and the substrates was analyzed
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