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Technical Briefs

Gas Turbine Aero-Engine First Stage Turbine Blade Failure Investigation

[+] Author and Article Information
Alaaeldin H. Mustafa

Mechanical Services Shops Department, Saudi Aramco, P.O. Box 6092, Dhahran 31311, Saudi Arabia

Hameed H. Badairy, Sudhir Mehta

Research and Development Center, Saudi Aramco, P.O. Box 6092, Dhahran 31311, Saudi Arabia

J. Eng. Gas Turbines Power 131(5), 054504 (Jun 05, 2009) (4 pages) doi:10.1115/1.3078782 History: Received August 06, 2008; Revised September 02, 2008; Published June 05, 2009

Plugging material in some of the film cooling channels of a failed aero-gas turbine engine first stage turbine blade is analyzed using the energy dispersive X-ray spectroscopy in an environmental scanning electron microscope. The objective of the analysis was to identify the nature and source of the plugging material that appears to have caused overheating and eventual failure of some of the blades. The results of the analysis indicate that the plugging material, which occurs as a dense aggregate of 0.1 m diameter fibers, is mainly composed of Zr, Y, and O. In addition, the material shows presence of micron size particles dispersed between the fibers. The analysis of the particles indicates they are fluoride-rich compounds, possibly of yttrium or calcium. Small or trace amounts of Ca, Na, and Mg are also observed in the plugging material. The analysis of the areas surrounding the plugged cooling channels shows presence of Cr–Co–Ni–aluminide bond coat and a discontinuous platinum coat over the bond coat. In contrast, the areas surrounding the fractured surface and melted edge show significant presence of calcium fluoride and Mg–Al–silicate. The analysis of melted edge shows presence of all the elements representing various coating layers as well as the impurities; however, Zr and Y were not detected in the melted areas.

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Copyright © 2009 by American Society of Mechanical Engineers
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Figures

Grahic Jump Location
Figure 4

(a) BSE image of a failed blade cross section showing formation of cracks through the Al–Pt–Ni rich layer 144×, (b) EDS X-ray spectrum of the base metal in the cross-sectional image shown in (a), (c) BSE image of the cross-sectional sample showing partial removal of the TBC from the surface 500×, (d) EDS X-ray spectrum of the Ni–Al–Pt rich layer shown as bright band in the cross-sectional image in (c)

Grahic Jump Location
Figure 3

(a) BSE image of a plugged cooling channel surrounded by bright particles on a gray matrix 40×, (b) EDS X-ray spectrum of the gray matrix in (a) indicating it is Cr–Co–Ni–aluminide bond coat on the blade. The bright areas are platinum on top of the bond coat. (c) ESEM image of an area near the melted edge of the blade showing accumulation of dark material 134×; (d) EDS X-ray spectrum of the dark material near the melted edge of the blade indicating it is most likely calcium fluoride with minor amounts of Mg–Al–silicate.

Grahic Jump Location
Figure 2

(a) BSE image of the plugging material showing aggregate of fibers underneath the smooth surface 502×; 2B EDS X-ray spectrum of fibers in (a) indicating they are mainly compounds of Zr and Y. The Ca and F peaks indicate the presence of Ca–F and/or Y–F compounds with the fibers. (c) BSE image of fibers and micron size particles in the plugging material 4000×; (d) EDS X-ray spectrum of fibers in (c) indicating the presence of Zr and Y. Notice the presence of strong fluorine peak probably originating from small particles with fibers.

Grahic Jump Location
Figure 1

(a) Photo micrograph showing whitish material plugging the cooling channels (red circle), (b) photo micrograph of the fractured surface of the failed turbine blade, (c) ESEM/BSE image of a plugging material in a cooling channel showing thick growth and fibrous fence surrounding the channel 101×, and (d) ESEM/BSE image of another plugged cooling channel. Notice the bright Pt-rich surface and polygonal cracks in the plugging material 134×.

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