OXIDATION BEHAVIOR OF TI6AL4V ALLOY EXPOSED TO ISOTHERMAL AND CYCLIC THERMAL TREATMENTS

1 Fargas Gemma
Co-authors:
1 Roa Joan Josep 1,2 Sefer Birhan 3 Pederson Robert 2 Antti Marta-Lena 1 Mateo Antonio
Institutions:
1 CIEFMA/EEBE, Departament de Ciència dels Materials i Enginyeria Metallúrgica
2 Universitat Politècnica de Catalunya, Barcelona, Spain, e-mail: gemma.fargas@upc.edu
2 Division of Materials Science, Luleä University of Technology, S-97187 Luleå, Sweden
3 Division of Welding Technology, University West, S-46186 Trollhättan, Sweden
Conference:
26th International Conference on Metallurgy and Materials, Hotel Voronez I, Brno, Czech Republic, EU, May 24th - 26th 2017
Proceedings:
Proceedings 26th International Conference on Metallurgy and Materials
Pages:
1573-1579
ISBN:
978-80-87294-79-6
ISSN:
2694-9296
Published:
9th January 2018
Proceedings of the conference were published in Web of Science and Scopus.
Metrics:
23 views / 14 downloads
Abstract

One of the most common titanium alloys for aerospace industry is Ti6Al4V (usually designed as Ti64) which is used for manufacturing aero-engine components, such as fan discs, compressor discs, blades and stators. The maximum service temperature for this alloy is limited partly because of degradation of mechanical properties at elevated temperatures (above 480 °C). During the first stage of oxidation the oxide scale is protective, whereas after prolonged oxidation time it loses its protective nature and favours higher diffusion of oxygen through the oxide. In the present study, cyclic thermal treatments were performed in air at 500 and 700 °C, up to 500 hours, and compared with similar studies carried out on isothermal oxidation conditions. The evolution of the surface oxidation was analyzed by metallographic techniques and X-ray diffraction, together with a detailed advanced characterization of the microstructure by Scanning Electron Microscopy and Focus Ions Beam. The results point out that the cyclic thermal treatments induced a strong increase of the weight gain compared to isothermal treatments. The analysis of the oxide scale revealed not only the presence of rutile, at 700 °C, but also anatase and TiOx at 500 °C for both isothermal and cyclic thermal treatments. At 700 °C, thermal stress caused by cyclic thermal treatments promoted the fracture of the oxide after the first 20 hours.

Keywords: Titanium, oxidation, isothermal treatments, cyclic thermal treatments
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