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20. Process and Mechanism of Removing Micro-Arc Oxidation Coating on Titanium Alloy by Plasma Electrolysis

Author

ZOU Yongchun, WANG Shuqi, WANG Yaming, CHEN Guoliang, ZHANG Kaiwei, OUYANG Jiahu, JIA Dechang, ZHOU Yu

Subjects
plasma electrolysis, coating removal, micro-arc oxidation, titanium alloy, Materials of engineering and construction. Mechanics of materials, TA401-492, Technology
Abstract

During the preparation and service process of micro-arc oxidation coatings，phenomena such as uneven growth or surface wear and peeling emerged，so the micro-arc oxidation coatings should be removed to achieve the purpose of secondary preparation and reuse.Aiming at the bottleneck problem of difficulty to remove micro-arc oxidation coating with high bonding strength，a novel plasma electrolytic removal(PER) technique was presented in this work.By comparing and analyzing the coating removal rates at different voltages，thickness change，and microstructure after coating removal at different times，it was found that the coating removal efficiency was the lowest with the applied voltage of 260 V，and the coating was completely removed after 11 min.When the voltage was increased to 320 V，the coating was completely removed in only 6 min.This was due to the large applied voltage，which made it easier to generate multiple and stable plasma discharge channels，thus realizing rapid removal of micro-arc oxidation coating.Furthermore，a synergistic mechanism of peeling，thinning，and dissolution in the removal of coatings by plasma electrolysis was proposed.The PER technique exhibits high efficiency and environmental protection，which has broad application prospects in the fields of aerospace，medical instruments and so on.

Published
2023
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21. Study on the Microstructure and High Temperature Oxidation Behavior of Micro-Arc Oxidation Coating on TC4 Alloy

Author

ZHAO Xinrui, WANG Shuqi, FU Boda, LU Yinsong, ZOU Yongchun, CHEN Guoliang, WANG Yaming

Subjects
tc4 alloy, micro-arc oxidation, microstructure, high temperature oxidation resistance, thermal shock resistance, Materials of engineering and construction. Mechanics of materials, TA401-492, Technology
Abstract

In order to improve the high temperature oxidation resistance of TC4 alloy，an anti-oxidation ceramic coating was prepared on the surface of titanium alloy by micro-arc oxidation in the NaAlO2+ Na3PO4 electrolyte system.The phase composition and microstructure of the coating were characterized by XRD，SEM and EDS，respectively.The hardness and elastic modulus of the coating were tested by nano indenter.In addition，the high temperature oxidation resistance and thermal shock resistance of the micro-arc oxidation coating were studied.Results showed that the surface of the micro-arc oxidation coating was porous.The coating was mainly composed of Al2TiO5 and rutile TiO2 phase.The nano hardness of microarc oxidation coating was (7.8 ± 0.6) GPa，significantly higher than that of TC4 alloy [(4.0 ± 0.2) GPa].After cyclic oxidation at 700 ℃for 80 h，the weight gain per unit area of micro-arc oxidation coating was only 0.73 mg/cm2，which was far less than the weight gains of TC4 alloy (20 mg/cm2)，showing good high temperature oxidation resistance.After 25 thermal shocks at 700 ℃，the coating had no scaling，indicating excellent thermal shock resistance.Hence，it could be seen that micro-arc oxidation coating could effectively prevent the diffusion of oxygen，significantly reducing the oxidation rate of titanium alloy and improving the high temperature oxidation resistance of titanium alloy.

Published
2023
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