Plasma electrolytic oxidation of cold spray kinetically metallized CNT-Al coating on AZ91-Mg alloy: Evaluation of mechanical and surficial characteristics

The cold-spray kinetically metallized (CS) carbon nanotube-aluminum (CNT-Al) and pure Al coatings were treated using plasma electrolytic oxidation (PEO) process to obtain CNT-Al+PEO and Al+PEO duplex coatings on AZ91 Mg alloy, respectively. The phase composition, microstructure, mechanical properties, wear and corrosion resistance of the PEO ceramic coatings were studied. The results showed that the PEO ceramic coating was mainly composed of alpha-Al2O3 and gamma-Al2O3, moreover, the small amount of CNT was also retained during the PEO process. The mechanical properties and wear resistance of the PEO ceramic coatings were significantly improved compared to the respective CS coatings. In particular, the hardness and elastic modulus of the PEO-CNT coating reached 13.9 GPa and 185.4 GPa, which were 21.0% and 23.4% higher than the respective CS coating. Moreover, the wear rate of the PEO-CNT coating was only 4.83 x 10(-5) mm(3)/N.m with a relatively low coefficient of friction of 0.65, which were 59.8% and 15.6% lower than the corresponding CS coating. The corrosion current density of the PEO-treated CNT-Al coating was 3.734 x 10(-6)A/cm(2), which was similar to the untreated CS coating. In short, the PEO treatment greatly improves the mechanical properties and wear resistance of the CS CNT-Al coating. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

The plasma electrolytic oxidation (PEO) treatment significantly improves the hardness, elastic modulus, and wear resistance of the carbon nanotube-aluminum (CNT-Al) coatings, making them more effective for applications on AZ91 Mg alloy.