Technical Briefs

Assessment of the Spent Life Fraction of Gas Turbine Blades by Coating Life Modeling and Photostimulated Luminescence Piezospectroscopy

[+] Author and Article Information
C. Rinaldi

 ERSE (exCESI RICERCA), via Rubattino 54, 20154 Milan, Italyclaudia.rinaldi@erse-web.it

L. De Maria

 ERSE, via Rubattino 54, 20154 Milan, Italy

M. Mandelli

 PROING ITALIA, via Coize 12, 38069 Torbole sul Garda (Trento), Italymandellimarco@interfree.it

J. Eng. Gas Turbines Power 132(11), 114501 (Aug 10, 2010) (4 pages) doi:10.1115/1.4000804 History: Received April 09, 2009; Revised November 20, 2009; Published August 10, 2010; Online August 10, 2010

This paper describes the application of a double-sided approach to assess the spent life fraction of thermal barrier coatings (TBCs) at local positions of ex-service blades with NiCoCrAlY-Re bond coat and EB-PVD TBC. A life prediction code implemented with inverse problem solution routines was applied to determine the mean local temperature. On the single blade, large differences (>150°C) of mean local temperature were estimated between regions just after the cooling holes and far from them. A self-developed portable photostimulated luminescence piezospectroscopy (PLPS) instrument was also applied and the coating spent life fraction was evaluated with a recently proposed PLPS diagnostic parameter. The spent life fractions evaluated from mean local temperature values were in good agreement with those estimated from PLPS measurements. Lower spent life fractions were found in well cooled regions of all blades, while higher spent life fractions were calculated at the hottest positions of the blades, particularly on components coming from a plant with a double number of starts. The results confirm the reliability of the PLPS technique and its diagnostic capability also for NiCoCrAlY-Re bond coats; both local differences on the single component and blade-to-blade variations in coating spent life can be evidenced in a nondestructive way.

Copyright © 2010 by American Society of Mechanical Engineers
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Figure 1

Example of NiCoCrAlYRe bond coat morphology on an ex-service blade

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Figure 2

Temperature (°C) values estimated with the IPS routine at midheight of the pressure side

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Figure 3

PLPS results along the pressure side of an ex-service blade. Notice film cooling beneficial effect (left arrows) and the position where the TBC life was exhausted (TBC detached during blade sectioning).

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Figure 4

TGO thickness and morphology observed on blade 1: (a) well cooled region, high |σTGO|; (b) center of blade, lower |σTGO|

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Figure 5

PLPS and estimated temperature values on blade 1 (150 cycles) at the pressure side center



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