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Preparation of Composite Coating with ZrO2 Nanoparticles on Aluminum 5052 Alloy Using Plasma Electrolytic Oxidation

Amiri Yarahmadi, Hossein | 2022

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 54876 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Ghorbani, Mohammad
  7. Abstract:
  8. Plasma Electrolytic Oxidation (PEO) method was used for the preparation of ceramic coatings on Aluminum 5052 substrate in a silicate-based electrolyte containing different concentrations of ZrO2 nanoparticles. Before the addition of nanoparticles into the electrolyte, determining process parameters including current density, coating time, and frequency were examined carefully. After studying corrosion behavior, thickness, and coating morphology in different circumstances, the frequency of 50Hz, the current density of 150mA/cm2, and the coating time of 20 minutes were chosen as the optimum parameters. After that and with the usage of those parameters, ZrO2 nanoparticles were added to the electrolyte in different concentrations. According to the obtained SEM images, it was found that the addition of zirconia nanoparticles had reduced the surface porosity of the coatings from 18.6% to 9.4%. This means that the morphology of the coatings became more uniform due to the addition of zirconia nanoparticles to the electrolyte. Moreover, reduction of the surface porosity led to an increase in corrosion resistance of the coatings. Results of the potentiodynamic polarization test showed that the corrosion current density decreased from 2.18×10-8 A/cm2 to 1.29×10-9 A/cm2 and the corrosion behavior of the coatings was improved. In addition, according to the results obtained from the EIS test, the outer porous layer's resistance had increased from 10.14 to 87.57 kΩcm2. Microhardness measurement results showed that by the application of PEO coatings the hardness of the substrate increased significantly and reached 825HV0.05. The presence of ZrO2 nanoparticles in electrolytes led to a further increase in hardness to 1120HV0.05
  9. Keywords:
  10. Plasma Electrolytic Oxidation ; Composite Coating ; Corrosion Resistance ; Aluminum Alloy 5052 ; Zirconia Nanoparticles ; Ceramic Coating

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