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Investigation on Effective Parameters in Ceramic Coating on Titanium Substrate by PEO Method in Galvano Static Condition

Fazeli Tehrani, Alimohammad | 2012

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 42667 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Faghihi Sani, Mohammad Ali
  7. Abstract:
  8. During this research, ceramic coatings on titanium substrate were prepared by plasma electrolytic oxidation process at a constant current density. Effect of different parameters such as frequency, current density, additives and time on the characteristics of the coated samples was studied. Composition, structure and elemental distribution of the coatings were studied by XRD, SEM and wave-length dispersive spectroscopy (WDS), respectively. Various tests were carried out to calculate the amount of coatings porosity. Pin-On-Disk method was used to evaluate erosion resistance of coatings. Corrosion and erosion-corrosion behaviors of the coatings were studied in 3.5wt% sodium chloride aqueous solution. Oxidation resistance of different samples was studied at 950˚c. In addition, thermal shock resistance of the coatings at high temperature was investigated. It was observed that surface properties of all coated specimens were improved in comparison with the bare substrate. The decrease in the size of porosities and coating thickness was the result of frequency increase. At high current densities, the size of porosities became larger although the coating thickness was decreased. With increase in process time, it was observed that the porosities size became larger erosion resistance of the coated samples improved due to the increase in coatings thickness. Addition of potassium hydroxide instead of sodium hydroxide to the electrolyte resulted in decrease in coatings thickness and erosion properties, because of the decrease in electrical conductivity of the electrolyte. The results also showed that the coatings prepared using sodium aluminate was the best among the other coatings, while the coatings prepared with sodium hexa meta phosphate had the worst properties
  9. Keywords:
  10. Titanium ; Plasma Electrolytic Oxidation ; Ceramic Coating ; Galvano Static

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