Erosion Performance of Gadolinium Zirconate-Based Thermal Barrier Coatings Processed by Suspension Plasma Spray
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Erosion Performance of Gadolinium Zirconate-Based Thermal Barrier Coatings Processed by Suspension Plasma Spray Satyapal Mahade1 • Nicholas Curry2 • Stefan Bjo¨rklund1 • Nicolaie Markocsan1 Per Nyle´n1 • Robert Vaßen3
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Submitted: 5 June 2016 / in revised form: 25 July 2016 ASM International 2016
Abstract 7-8 wt.% Yttria-stabilized zirconia (YSZ) is the standard thermal barrier coating (TBC) material used by the gas turbines industry due to its excellent thermal and thermo-mechanical properties up to 1200 C. The need for improvement in gas turbine efficiency has led to an increase in the turbine inlet gas temperature. However, above 1200 C, YSZ has issues such as poor sintering resistance, poor phase stability and susceptibility to calcium magnesium alumino silicates (CMAS) degradation. Gadolinium zirconate (GZ) is considered as one of the promising top coat candidates for TBC applications at high temperatures ([1200 C) due to its low thermal conductivity, good sintering resistance and CMAS attack resistance. Single-layer 8YSZ, double-layer GZ/YSZ and triplelayer GZdense/GZ/YSZ TBCs were deposited by suspension plasma spray (SPS) process. Microstructural analysis was carried out by scanning electron microscopy (SEM). A columnar microstructure was observed in the single-, double- and triple-layer TBCs. Phase analysis of the assprayed TBCs was carried out using XRD (x-ray diffraction) where a tetragonal prime phase of zirconia in the
This article is an invited paper selected from presentations at the 2016 International Thermal Spray Conference, held May 10-12, 2016, in Shanghai, P. R. China, and has been expanded from the original presentation. & Satyapal Mahade [email protected] 1
Department of Engineering Science, University West, Trollha¨ttan, Sweden
2
Treibacher Industrie AG, Althofen, Austria
3
Institute of Energy and Climate Research (IEK-1), Forschungszentrum Ju¨lich GmbH, Ju¨lich, Germany
single-layer YSZ TBC and a cubic defect fluorite phase of GZ in the double and triple-layer TBCs was observed. Porosity measurements of the as-sprayed TBCs were made by water intrusion method and image analysis method. The as-sprayed GZ-based multi-layered TBCs were subjected to erosion test at room temperature, and their erosion resistance was compared with single-layer 8YSZ. It was shown that the erosion resistance of 8YSZ single-layer TBC was higher than GZ-based multi-layered TBCs. Among the multi-layered TBCs, triple-layer TBC was slightly better than double layer in terms of erosion resistance. The eroded TBCs were cold-mounted and analyzed by SEM. Keywords columnar microstructure erosion test gadolinium zirconate multi-layered thermal barrier coating suspension plasma spray yttria-stabilized zirconia
Introduction Thermal barrier coatings (TBC) are used in the hot sections of land-based and aero gas turbine engine components to insulate the underlying metallic material from high temperatures. 7-8 wt.% YSZ is the standard ceramic material used for TBC applications due to its
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