Title

Phase Transformations Of Thermally Grown Oxide On (Ni,Pt)Al Bondcoat During Electron Beam Physical Vapor Deposition And Subsequent Oxidation

Keywords

Electron beam physical vapour deposition; Oxidation; Phase transformation; Photostimulate luminescence spectroscopy; Thermal barrier coatings

Abstract

Phase constituents, morphology and microstructure of thermally grown oxide (TGO) as a function of electron beam physical vapor deposition (EP-PVD) time, (Ni,Pt)Al bondcoat surface treatment and subsequent oxidation in air were examined for a series of thermal barrier coatings (TBCs). Photostimulated luminescence spectroscopy (PSLS) and focused ion beam (FIB) in-situ lift-out (INLO) specimen preparation for (scanning) transmission electron microscopy were employed to characterize the TBCs. Photostimulated luminescence only from α-Al2O3 was observed on grit-blasted bondcoat for all YSZ deposition times, while that from metastable Al2O3 phases including α-Al2O3 was observed for the TGO on as-coated (i.e. not grit blasted) bondcoat. Relative to the luminescence intensity of the α-Al2O3, the luminescence intensity from the metastable Al2O3 phases decreased with an increase in deposition time and corresponding thickness of ZrO2-Y2O3 (YSZ). On subsequent oxidation in air at 1000, 1050 and 1100 °C for 0.5, 10 and 50 h, the luminescence intensity from the metastable Al2O3 phases decreased while that of α-Al2O3 increased. These observations regarding the phase constituents of TGO were confirmed by diffraction analysis using high resolution TEM (HR-TEM) via FIB INLO. The initial development of the TGO during EB-PVD deposition consisted of a mixed-oxide zone. The relative thickness of the mixed-oxide zone for TGO formed on the as-coated bondcoat surface was greater than that of TGO formed on grit-blasted bondcoat surface. The variation in the presence of metastable Al2O3 in the TGO for as-processed TBCs was observed to influence the overall growth of TGO during short-term isothermal oxidation, particularly as the temperature decreased © 2003 Elsevier B.V. All rights reserved.

Publication Date

1-30-2004

Publication Title

Surface and Coatings Technology

Volume

177-178

Number of Pages

121-130

Document Type

Article

Personal Identifier

scopus

DOI Link

https://doi.org/10.1016/j.surfcoat.2003.08.072

Socpus ID

1342332697 (Scopus)

Source API URL

https://api.elsevier.com/content/abstract/scopus_id/1342332697

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