High resolution STEM investigations of TGO formed in TBCs on ɣ-TiAl with CHC-PVD TiAlCrYSi bond coatings

The paper deals with high temperature oxidation behavior of EB-PVD TBCs on a 48–2–2 TiAl alloy with a TiAlCrYSi bond coating. The samples were subjected to the cyclic oxidation test at 900 °C in 1-hour cycles up to 1000 cycles. Special focus was paid to STEM investigations of the interfacial phenome...

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Bibliographic Details
Published in:Corrosion science 2022-05, Vol.200, p.110225, Article 110225
Main Authors: Swadźba, Radosław, Bauer, Peter-Philipp
Format: Article
Language:English
Subjects:
Aluminum oxide
Coatings
Grain boundaries
High temperature
High temperature oxidation
Intermetallic compounds
Oxidation
Oxidation tests
Reactive element effect
STEM
Titanium aluminides
Titanium base alloys
Titanium dioxide
Transitional aluminas
Yttrium
Yttrium oxide
ɣ-TiAl
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Summary:The paper deals with high temperature oxidation behavior of EB-PVD TBCs on a 48–2–2 TiAl alloy with a TiAlCrYSi bond coating. The samples were subjected to the cyclic oxidation test at 900 °C in 1-hour cycles up to 1000 cycles. Special focus was paid to STEM investigations of the interfacial phenomena occurring in the TBCs. The pre-oxidation treatment resulted in formation of a thermally grown oxide with outer Cr-rich γ-Al2O3 as well as nanometric TiO2, Y2O3 and Y3Al5O12 and inner α-Al2O3 that grew during the oxidation test at 900 °C. Yttrium segregation to α-Al2O3 grain boundaries was evidenced using STEM. •Initial TGO consists of Cr-rich ɣ-Al2O3 with nanometric TiO2, Y3Al5O12 and Y2O3.•Internal zone of the TGO contains Cr-free α-Al2O3 at the scale/metal interface.•7YSZ top coating remains adherent up to 1000 1-hour cycles at 900 °C.•TiAlCrYSi bond coating provides 0.42 mg/cm2 of mass gain during 1000 cycles at 900 °C.•Yttrium segregation found at α-Al2O3 grain boundaries after the cyclic oxidation test.
ISSN:0010-938X
1879-0496
DOI:10.1016/j.corsci.2022.110225