Formation and structure of sphene/titania composite coatings on titanium formed by a hybrid technique of microarc oxidation and heat-treatment |
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Authors: | Su ChengDaqing Wei Yu Zhou |
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Institution: | Institute for Advanced Ceramics, Department of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001, PR China |
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Abstract: | Sphene/titania composite coatings were fabricated on titanium by a hybrid technique of microarc oxidation (MAO) and heat treatment. The high-applied voltages promote the formation of sphene in the MAO coatings after heat-treatment. Heat treatment could change the surface morphology of the MAO coatings such as roughness, macropores size and density and the thickness of the MAO coatings. Increasing the heat-treatment temperature decreased the atomic concentration ratios of Ti/Si and Ti/Ca of the MAO coatings. The chemical states of Ti4+, Ca2+, Si2+ and O2− were observed on all the coatings. Additionally, Ti2+ was detected in the MAO and heat-treated MAO coatings at 600 and 700 °C. The heat-treatment has obvious effect on the chemical states of Si, Ti and O elements due to the formation of sphene and oxidation of TiO phase of the MAO coating, but did not affect that of Ca. In the heat-treated MAO coatings at 800 °C (MAO-H8), the titanium surface shows a MAO top layer and oxidized interior layer. A concentration gradient in components in the MAO layer of the MAO-H8 coating was formed. |
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Keywords: | Titanium Sphene Titania Microarc oxidation Heat-treatment |
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