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Al2O3-ZrO2 nanostructured coatings using DC plasma electrolytic oxidation to improve tribological properties of Al substrates

Barati, N ; Sharif University of Technology | 2015

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  1. Type of Document: Article
  2. DOI: 10.1016/j.apsusc.2015.08.188
  3. Publisher: Elsevier , 2015
  4. Abstract:
  5. Alumina-zirconia nanostructured coatings were formed on 7075 Al alloy through Plasma Electrolytic Oxidation (PEO) operated in aDC potentiostatic mode. The composite coatings were produced in the range of 425-500 V in an alkaline electrolyte containing 4 g/LK2ZrF6. Tribological properties of coatings were investigated using dry sliding wear test against WC balls with a pin-on-disc tribometer. Wear rates were evaluated using optical profilometer. It was shown that the nanostructured alumina-zirconia composite coatings can be formed at voltages 450 V. The coating thickness and roughness were in the range of 15.2-24.2 μm and 0.68-2.35 μm, respectively. The distribution of Al, Zr and O in the coatings was uniform. Increasing the PEO voltage led to porosity increment and formation of the high temperature tetragonal zirconia phase (t-ZrO2). Significant enhancement in tribological properties for coated samples was achieved: under optimum conditions, corresponding to the PEO treatment at 500 V for 200 s, the coating wear rate of 2.62 × 10-6 mm3 N-1 m-1 and friction coefficient of 0.22 were recorded that are about 120 and 3 times lower than those for the substrate
  6. Keywords:
  7. Alumina ; Aluminum ; Aluminum coatings ; Electrolysis ; Electrolytes ; Friction ; Oxidation ; Substrates ; Thickness measurement ; Tribology ; Tungsten carbide ; Wear of materials ; Zirconia ; Alkaline electrolytes ; Alumina zirconia composites ; Dry sliding wear test ; Friction coefficients ; Nanostructured coatings ; Pin on disc tribometer ; Plasma electrolytic oxidation ; Tribological properties ; Composite coatings
  8. Source: Applied Surface Science ; Volume 356 , November , 2015 , Pages 927-934 ; 01694332 (ISSN)
  9. URL: http://www.sciencedirect.com/science/article/pii/S0169433215020127