TGO formation and oxygen diffusion in Al-rich gamma-TiAl PVD-coatings on TNM alloys. (15th March 2022)

• Record Type: Journal Article
• Authors: Kagerer, S.; Hudak, O.E.; Schloffer, M.; Riedl, H.; Mayrhofer, P.H.
• Is Part Of: Scripta materialia. Number 210(2022)
• Publication Date: 2022-03-15
• Subjects: Oxidation resistance -- γ-TiAl -- TNM -- Diffusion coefficients -- PVD -- Protection coatings; Materials -- Periodicals; Metallurgy -- Periodicals; Metalen; Legeringen; Materiaalkunde; Metals, metalworking and machinery industries; Metals; Electronic journals; 620.11
• DOI: 10.1016/j.scriptamat.2021.114455
• Languages: English
• ISSNs: 1359-6462

Abstract

Abstract: γ-TiAl alloys have gained much attention due to their low density, excellent fatigue resistance, and high specific strength at elevated temperatures. Throughout this study, we showcase physical vapor deposited Al-rich γ-TiAl coatings as a considerable solution to extend the durability and longevity of γ-TiAl bulk materials in high temperature regimes (> 750 °C). In detail, the oxidation resistance is enhanced up to at least 850 °C for 1000 h, whilst exhibiting a maximum oxygen affected area of 8.4 µm (16 µm coating). Based on various oxidation treatments (800, 850, and 900 °C), we estimated a mean parabolic rate constant of about 1.03∙10 −10 cm²/h and a logarithmic oxygen inward diffusion rate of approximately 1.20∙10 −4 cm/h. The corresponding activation energies validate the considerably retarded oxide scale kinetics – particularly, for the thermally grown oxides. Furthermore, the thermal exposure introduced excellent intermixing between the Al-rich γ-TiAl coating and γ-TiAl bulk material, resulting in a coalescence of the coating-substrate interface. Graphical abstract: Image, graphical abstract