Depth-Resolved Porosity Investigation of EB-PVD Thermal Barrier Coatings Using High-Energy X-Rays

Published

February 1, 2004

Author(s)

A Kulkarni, H Herman, J Almer, U Lienert, D Haeffner

Abstract

Demands for designing prime reliant, energy efficient and high performance thermal barrier coatings (TBCs) in gas turbines have led to growing interest towards comprehensive microstructural characterization. Here we investigate novel use of high-energy x-rays for small-angle x-ray scattering (SAXS), together with wide angle scattering and radiography, for depth resolved characterization of TBCs grown by electron beam physical vapor deposition. Such coatings are of particular interest due to their high strain tolerance and thermal shock resistance. The coating microstructure is found to consist of columns perpendicular to the substrate, extending through the thickness, with [001] growth-texture and significant intercolumnar porosity. Also, overshadowing effects and gas entrapment result in nano-scale intracolumnar porosity consisting of feather-like and globular shapes. Radiography showed an increase in total porosity, from 15% to 25%, from near substrate to coating surface, which is ascribed to an increase in the intercolumnar spacing at the top of the coating. By contrast, the small angle scattering studies, which are sensitive to fine features, showed the surface area of the pores to be the largest near the substrate.

Citation

Journal of the American Ceramic Society

Volume

87

Issue

No. 2

Pub Type

Journals

Keywords

electron-beam physical vapor deposition, microstructure, small-angle x-ray scattering, thermal barrier deposits

Citation

Kulkarni, A. , Herman, H. , Almer, J. , Lienert, U. and Haeffner, D. (2004), Depth-Resolved Porosity Investigation of EB-PVD Thermal Barrier Coatings Using High-Energy X-Rays, Journal of the American Ceramic Society (Accessed July 21, 2024)