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Combined Al- plus F-treatment of Ti-alloys for improved behaviour at elevated temperatures / A. Donchev in Materials and corrosion, Vol. 62 N° 7 (Juillet 2011) 

Public ISBD [article]  in Materials and corrosion > Vol. 62 N° 7 (Juillet 2011) . - pp. 695–698 Titre : Combined Al- plus F-treatment of Ti-alloys for improved behaviour at elevated temperatures Type de document : texte imprimé Auteurs : A. Donchev, Auteur ; A. Kolitsch, Auteur ; M. Schutze, Auteur Année de publication : 2011 Article en page(s) : pp. 695–698 Note générale : Génie Mécanique Langues : Anglais (eng) Mots-clés : Environmental  embrittlement  Oxidation  Titanium Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Titanium is a widely used structural material because of its low specific weight, good mechanical properties and excellent corrosion resistance at ambient temperature. As a result of increased oxidation at elevated temperatures and environmental embrittlement the maximum operation temperature of standard Ti-alloys is only about 600 °C. The oxidation behaviour can be improved by different methods, e.g. coatings. This leads to an improvement which is, however, often limited. The combination of Al-enrichment in the sub surface zone, so that a TiAl-layer is formed, plus F-treatment gives impressively good results because a protective alumina scale is formed due to the fluorine effect. This alumina scale prevents oxygen inward diffusion which causes embrittlement and protects the material against environmental attack. The procedure is applied to alloys with a very low Al-content or even no Al at all. In the paper results of oxidation tests of α-Ti without any treatment, with Al-treatment and with a combination of Al- + F-treatment are presented. Aluminium was diffused into the samples by a powder pack process. Fluorine was applied by a liquid phase process. The formation of an alumina scale on treated samples was revealed by post experimental investigations. The results are discussed referring to the fluorine effect model for TiAl-alloys. DEWEY : 620.1 ISSN : 0947-5117 En ligne : http://onlinelibrary.wiley.com/doi/10.1002/maco.201005870/abstract [article] Combined Al- plus F-treatment of Ti-alloys for improved behaviour at elevated temperatures [texte imprimé] / A. Donchev, Auteur ; A. Kolitsch, Auteur ; M. Schutze, Auteur . - 2011 . - pp. 695–698. Génie Mécanique Langues : Anglais (eng) in Materials and corrosion > Vol. 62 N° 7 (Juillet 2011) . - pp. 695–698 Mots-clés : Environmental  embrittlement  Oxidation  Titanium Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Titanium is a widely used structural material because of its low specific weight, good mechanical properties and excellent corrosion resistance at ambient temperature. As a result of increased oxidation at elevated temperatures and environmental embrittlement the maximum operation temperature of standard Ti-alloys is only about 600 °C. The oxidation behaviour can be improved by different methods, e.g. coatings. This leads to an improvement which is, however, often limited. The combination of Al-enrichment in the sub surface zone, so that a TiAl-layer is formed, plus F-treatment gives impressively good results because a protective alumina scale is formed due to the fluorine effect. This alumina scale prevents oxygen inward diffusion which causes embrittlement and protects the material against environmental attack. The procedure is applied to alloys with a very low Al-content or even no Al at all. In the paper results of oxidation tests of α-Ti without any treatment, with Al-treatment and with a combination of Al- + F-treatment are presented. Aluminium was diffused into the samples by a powder pack process. Fluorine was applied by a liquid phase process. The formation of an alumina scale on treated samples was revealed by post experimental investigations. The results are discussed referring to the fluorine effect model for TiAl-alloys. DEWEY : 620.1 ISSN : 0947-5117 En ligne : http://onlinelibrary.wiley.com/doi/10.1002/maco.201005870/abstract