Effects of Current Density in Electrolyte Containing Graphene on Properties of 2024 Aluminum Alloy Micro-arc Oxidation Coating

TANG Yu-hao, XIANG Dong, LI Dong-hao, WANG Lei, WANG Ping, HAN Pei-dong

Surface Technology ›› 2018, Vol. 47 ›› Issue (7) : 203-208.

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Surface Technology ›› 2018, Vol. 47 ›› Issue (7) : 203-208. DOI: 10.16490/j.cnki.issn.1001-3660.2018.07.029
Surface Failure and Protection

Effects of Current Density in Electrolyte Containing Graphene on Properties of 2024 Aluminum Alloy Micro-arc Oxidation Coating

  • TANG Yu-hao1, XIANG Dong1, LI Dong-hao1, WANG Lei1, WANG Ping1, HAN Pei-dong2
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Abstract

The work aims to study effects of current density on thickness, hardness and wear resistance, corrosion resistance of MAO coating. Graphene nanoplatelets (GNPs) was added to the electrolyte containing sodium hydroxide and sodium silicate, micro-arc oxidation (MAO) treatment of 2024 aluminum alloy was completed at different current density in the mode of pulsed direct current. Morphology and composition of the coating were analyzed using scanning electron microscope (SEM) and energy dispersive spectrometer (EDS); corrosion resistance of the coating was tested using polarization curve; phase composition of the sample was characterized with X-ray diffractometer (XRD); surface mechanical property of the ceramic coating was determined with multi-functional material surface performance testing machine. Current density increased from 1 A/dm2 to 5 A/dm2, thickness of coating containing GNPs increased from 4.2 μm to 5.8 μm, thickness of GNPs-free coating increased from 2.7 μm to 4.5 μm. After MAO treatment at initial current density of 1 A/dm2, the hardness of the coating containing GNPs was up to 163HV, 63% higher than that of GNPs-free coating. Friction coefficient was about 0.5 when current density was 1 A/dm2, and it decreased to 0.3 as current density reached 5 A/dm2, which improved wear resistance of coatings. At the current density of 3 A/dm2, self-corrosion potential increased gradually, and corrosion current tended to decrease, and corrosion resistance of the ceramic coating was the best. Current density had no obvious effects on composition of the ceramic coating. Friction coefficient of compact layer in the sample significantly decreases and wear resistance improves as current density increases. Higher current density can effectively reduce number and size of discharge holes on the coating, and improve corrosion resistance of the coating. The coating exhibits the best corrosion resistance at the current density of 3 A/dm2. Thickness, hardness, abrasive resistance and corrosion resistance of the coating can be improved by adding GNPs.

Key words

2024 aluminum alloy; micro-arc oxidation; current density; graphene; hardness; abrasive resistance; corrosion resistance

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TANG Yu-hao, XIANG Dong, LI Dong-hao, WANG Lei, WANG Ping, HAN Pei-dong. Effects of Current Density in Electrolyte Containing Graphene on Properties of 2024 Aluminum Alloy Micro-arc Oxidation Coating[J]. Surface Technology. 2018, 47(7): 203-208

Funding

Sichuan International Scientific and Technological Cooperation and Exchange Research and Development Project (2017HH0086); the Seventeenth Phase Open Experiment Major Project of Southwest Petroleum University (KSZ17121)
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