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Mechanical and barrier properties of MOCVD processed alumina coatings on Ti6Al4V titanium alloy

Balcaen, Yannick and Radutoiu, Nicoleta and Alexis, Joël and Béguin, Jean-Denis and Lacroix, Loïc and Samélor, Diane and Vahlas, Constantin Mechanical and barrier properties of MOCVD processed alumina coatings on Ti6Al4V titanium alloy. (2011) Surface and Coatings Technology, vol. 206 (n° 7). pp. 1684-1690. ISSN 0257-8972

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Official URL: http://dx.doi.org/10.1016/j.surfcoat.2011.09.056

Abstract

This study focuses on the implementation of different aluminum oxide coatings processed by metal-organic chemical vapor deposition from aluminum tri-isopropoxide on commercial Ti6Al4V titanium alloy to improve its high temperature corrosion resistance. Films grown at 350 °C and at 480 °C are amorphous and correspond to formulas AlOOH, and Al2O3, respectively. Those deposited at 700 °C are composed of γ-Al2O3 nanocrystals dispersed in a matrix of amorphous alumina. Their mechanical properties and adhesion to the substrates were investigated by indentation, scratch and micro tensile tests. Hardness and rigidity of the films increase with increasing deposition temperature. The hardness of the coatings prepared at 350 °C and 480 °C is 5.8 ± 0.7 GPa and 10.8 ± 0.8 GPa respectively. Their Young's modulus is 92 ± 8 GPa (350 °C) and 155 ± 6 GPa (480 °C). Scratch tests cause adhesive failures of the films grown at 350 °C and 480 °C whereas cohesive failure is observed for the nanocrystalline one, grown at 700 °C. Micro tensile tests show a more progressive cracking of the latter films than on the amorphous ones. The films allow maintaining good mechanical properties after corrosion with NaCl deposit during 100 h at 450 °C. After corrosion test only the film deposited at 700 °C yields an elongation at break comparable to that of the as processed samples without corrosion. The as established processing–structure–properties relation paves the way to engineer MOCVD aluminum oxide complex coatings which meet the specifications of the high temperature corrosion protection of titanium alloys with regard to the targeted applications.

Item Type:Article
Additional Information:Thanks to Elsevier editor. The orinal version is available at http://www.sciencedirect.com The original PDF of the article can be found at Surface and Coatings Technology website: http://www.sciencedirect.com/science/article/pii/S0257897211009431
Audience (journal):International peer-reviewed journal
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Institution:French research institutions > Centre National de la Recherche Scientifique - CNRS
Université de Toulouse > Institut National Polytechnique de Toulouse - INPT
Université de Toulouse > Université Paul Sabatier-Toulouse III - UPS
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Deposited By: Denis Faragou

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