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Functional performance of Gd2Zr2O7/YSZ multi-layered thermal barrier coatings deposited by suspension plasma spray
University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing. (PTW)ORCID iD: 0000-0003-2475-9284
University West, Department of Engineering Science, Division of Manufacturing Processes. (PTW)ORCID iD: 0000-0003-0209-1332
University West, Department of Engineering Science, Division of Mechanical Engineering. (PTW)ORCID iD: 0000-0003-1181-0415
University West, Department of Engineering Science, Division of Manufacturing Processes. (PTW)ORCID iD: 0000-0002-9578-4076
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2016 (English)In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347Article in journal (Refereed) Epub ahead of print
Abstract [en]

7-8 wt% yttria stabilized zirconia (YSZ) is the standard ceramic top coat material used in gasturbines to insulate the underlying metallic substrate. However, at higher temperatures(>1200 °C), phase stability and sintering becomes an issue for YSZ. At these temperatures,YSZ is also susceptible to CMAS (calcium magnesium alumino silicates) infiltration. New ceramic materials such as pyrochlores have thus been proposed due to their excellent properties such as lower thermal conductivity and better CMAS attack resistance compared to YSZ. However, pyrochlores have inferior thermo mechanical properties compared to YSZ.Therefore, double-layered TBCs with YSZ as the intermediate layer and pyrochlore as the top ceramic layer have been proposed. In this study, double layer TBC comprising gadoliniumzirconate (GZ)/YSZ and triple layer TBC (GZdense/GZ/YSZ) comprising relatively denser GZtop layer on GZ/YSZ were deposited by suspension plasma spray. Also, single layer 8YSZ TBC was suspension plasma sprayed to compare its functional performance with the multilayered TBCs. Cross sections and top surface morphology of as sprayed TBCs were analyzed by scanning electron microscopy (SEM). XRD analysis was done to identify phases formed in the top surface of as sprayed TBCs. Porosity measurements were made using water intrusionand image analysis methods. Thermal diffusivity of the as sprayed TBCs was measured using laser flash analysis and thermal conductivity of the TBCs was calculated. The multi-layered GZ/YSZ TBCs were shown to have lower thermal conductivity than the single layer YSZ. Theas sprayed TBCs were also subjected to thermal cyclic testing at 1300 ºC. The double and triple layer TBCs had a longer thermal cyclic life compared to YSZ. The failed samples were cold mounted and analyzed by SEM.

Place, publisher, year, edition, pages
2016.
Keyword [en]
Columnar microstructure, Gadolinium zirconate, Multi-layered thermal barrier coating, Suspension plasma spray, Thermal conductivity, Thermal cyclic test, Yttria stabilized zirconia
National Category
Production Engineering, Human Work Science and Ergonomics
Research subject
Production Technology; ENGINEERING, Manufacturing and materials engineering
Identifiers
URN: urn:nbn:se:hv:diva-9855DOI: 10.1016/j.surfcoat.2016.12.062OAI: oai:DiVA.org:hv-9855DiVA: diva2:957977
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Ingår i licuppsats

Available from: 2016-09-05 Created: 2016-09-05 Last updated: 2017-01-04Bibliographically approved
In thesis
1. Functional Performance of Gadolinium Zirconate/Yttria Stabilized Zirconia Multi-Layered Thermal Barrier Coatings
Open this publication in new window or tab >>Functional Performance of Gadolinium Zirconate/Yttria Stabilized Zirconia Multi-Layered Thermal Barrier Coatings
2016 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Yttria stabilized zirconia (YSZ) is the state of the art ceramic top coat material used for TBC applications. The desire to achieve a higher engine efficiency of agas turbine engine by increasing the turbine inlet temperature has pushed YSZ toits upper limit. Above 1200°C, issues such as poor phase stability, high sinteringrates, and susceptibility to CMAS (calcium magnesium alumino silicates) degradation have been reported for YSZ based TBCs. Among the new materials,gadolinium zirconate (GZ) is an interesting alternative since it has shown attractive properties including resistance to CMAS attack. However, GZ has a poor thermo-chemical compatibility with the thermally grown oxide leading to poor thermal cyclic performance of GZ TBCs and that is why a multi-layered coating design seems feasible.This work presents a new approach of depositing GZ/YSZ multi-layered TBCs by the suspension plasma spray (SPS) process. Single layer YSZ TBCs were also deposited by SPS and used as a reference.The primary aim of the work was to compare the thermal conductivity and thermal cyclic life of the two coating designs. Thermal diffusivity of the YSZ single layer and GZ based multi-layered TBCs was measured using laser flash analysis (LFA). Thermal cyclic life of as sprayed coatings was evaluated at 1100°C, 1200°C and 1300°C respectively. It was shown that GZ based multi-layered TBCs had a lower thermal conductivity and higher thermal cyclic life compared to the single layer YSZ at all test temperatures. The second aim was to investigate the isothermal oxidation behaviour and erosion resistance of the two coating designs. The as sprayed TBCs were subjected toisothermal oxidation test at 1150°C. The GZ based multi-layered TBCs showed a lower weight gain than the single layer YSZ TBC. However, in the erosion test,the GZ based TBCs showed lower erosion resistance compared to the YSZ singlelayer TBC. In this work, it was shown that SPS is a promising production technique and that GZ is a promising material for TBCs.

Place, publisher, year, edition, pages
Trollhättan: University West, 2016. 70 p.
Series
Licentiate Thesis: University West, 11
Keyword
Erosion, Gadolinium Zirconate, Suspension Plasma Spray, Thermal Barrier Coatings, Thermal Cyclic Test, Thermal Conductivity, Yttria Stabilized Zirconia
National Category
Manufacturing, Surface and Joining Technology
Research subject
Production Technology
Identifiers
urn:nbn:se:hv:diva-9854 (URN)978-91-87531-36-1 (ISBN)978-91-87531-37-8 (ISBN)
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Available from: 2016-09-09 Created: 2016-09-05 Last updated: 2016-09-06Bibliographically approved

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Mahade, SatyapalCurry, NicholasBjörklund, StefanMarkocsan, NicolaieNylén, Per
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