| Autor: |
Laska, Nadine, Watermeyer, Philipp, Koliotassis, Lisa, Braun, Reinhold |
| Předmět: |
|
| Zdroj: |
Materials at High Temperatures; Jan-May2018, Vol. 35 Issue 1-3, p187-194, 8p, 1 Color Photograph, 4 Black and White Photographs, 3 Charts, 1 Graph |
| Abstrakt: |
Intermetallic titanium aluminide alloys are attractive light-weight materials for high temperature applications in automotive and aero engines. The development of γ-TiAl alloys over the past decades has led to their successful commercial application as low pressure turbine blades. The operating temperatures of γ-TiAl based alloys are limited by deterioration in strength and creep resistance at elevated temperatures as well as poor oxidation behaviour above 800 °C. Since improvement in oxidation behaviour of γ-TiAl based alloys without impairing their mechanical properties represents a major challenge, intermetallic protective coatings have aroused increasing interest in the last years.In this work, a 10 μm thick intermetallic Ti-46Al-36Cr-4Zr (in at.-%) coating was applied on a TNB alloy using magnetron sputtering. This layer provided excellent oxidation protection up to 1000 °C. Microstructural changes in this coating during the high temperature exposure were extensively investigated using scanning and transmission electron microscopy. The coating developed a three-phase microstructure consisting of the hexagonal Laves-phase Ti(Cr,Al)2, the tetragonal Cr2Al phase and the cubic τ-TiAl3 phase. After long-term exposure the three-phase microstructure changed to a two-phase microstructure of the hexagonal α2-Ti3Al phase and an orthorhombic body-centred phase, whose crystal structure has not yet been definitely identified. On the coating, a thin protective alumina scale formed. Applying this intermetallic layer as bond coat, thermal barrier coatings (TBCs) of yttria partially stabilized zirconia were deposited on γ-TiAl based TNB samples using electron-beam physical vapour deposition. The results of cyclic oxidation testing (1 h at elevated temperature, 10 min. cooling at ambient temperature) revealed a TBC lifetime of more than 1000 h of cyclic exposure to air at 1000 °C. The ceramic topcoat exhibited an excellent adhesion to the thermally grown alumina scale which contained fine ZrO2 precipitates. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
| Externí odkaz: |
|
|
Nepřihlášeným uživatelům se plný text nezobrazuje |
K zobrazení výsledku je třeba se přihlásit.
|
