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Jonnalagadda, K. P., Mahade, S., Kramer, S., Zhang, P., Curry, N., Li, X.-H. & Peng, R. L. (2019). Failure of Multilayer Suspension Plasma Sprayed Thermal Barrier Coatings in the Presence of Na2SO4 and NaCl at 900 °C. Journal of thermal spray technology (Print), 28(1-2), 212-222
Open this publication in new window or tab >>Failure of Multilayer Suspension Plasma Sprayed Thermal Barrier Coatings in the Presence of Na2SO4 and NaCl at 900 °C
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2019 (English)In: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 28, no 1-2, p. 212-222Article in journal (Refereed) Published
Abstract [en]

The current investigation focuses on understanding the influence of a columnar microstructure and a sealing layer on the corrosion behavior of suspension plasma sprayed thermal barrier coatings (TBCs). Two different TBC systems were studied in this work. First is a double layer made of a composite of gadolinium zirconate + yttria stabilized zirconia (YSZ) deposited on top of YSZ. Second is a triple layer made of dense gadolinium zirconate deposited on top of gadolinium zirconate + YSZ over YSZ. Cyclic corrosion tests were conducted between 25 and 900 °C with an exposure time of 8 h at 900 °C. 75 wt.% Na2SO4 + 25 wt.% NaCl were used as the corrosive salts at a concentration of 6 mg/cm2. Scanning electron microscopy analysis of the samples’ cross sections showed that severe bond coat degradation had taken place for both the TBC systems, and the extent of bond coat degradation was relatively higher in the triple-layer system. It is believed that the sealing layer in the triple-layer system reduced the number of infiltration channels for the molten salts which resulted in overflowing of the salts to the sample edges and caused damage to develop relatively more from the edge.

Keywords
columnar microstructure, composite of gadolinium zirconate and YSZ, hot corrosion, suspension plasma spray
National Category
Manufacturing, Surface and Joining Technology
Research subject
ENGINEERING, Manufacturing and materials engineering; Production Technology
Identifiers
urn:nbn:se:hv:diva-13100 (URN)10.1007/s11666-018-0780-5 (DOI)000456599500019 ()2-s2.0-85055998259 (Scopus ID)
Funder
VINNOVA
Note

First Online: 29 October 2018

This article is an invited paper selected from presentations at the 2018 International Thermal Spray Conference, held May 7-10, 2018, in Orlando, Florida, USA, and has been expanded from the original presentation.

Available from: 2018-11-06 Created: 2018-11-06 Last updated: 2019-02-12Bibliographically approved
Mahade, S., Curry, N., Jonnalagadda, K. P., Peng, R. L., Markocsan, N. & Nylén, P. (2019). Influence of YSZ layer thickness on the durability of gadolinium zirconate/YSZ double-layered thermal barrier coatings produced by suspension plasma spray. Surface & Coatings Technology, 357, 456-465
Open this publication in new window or tab >>Influence of YSZ layer thickness on the durability of gadolinium zirconate/YSZ double-layered thermal barrier coatings produced by suspension plasma spray
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2019 (English)In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 357, p. 456-465Article in journal (Refereed) Published
Abstract [en]

In this work, three double layered thermal barrier coating (TBC) variations with different gadolinium zirconate (GZ) and YSZ thickness (400GZ/100YSZ, 250GZ/250YSZ and 100GZ/400YSZ respectively, where the prefixed numbers before GZ and YSZ represent the layer thickness in μm), were produced by suspension plasma spray (SPS) process. The objective was to investigate the influence of YSZ thickness on the thermal conductivity and thermal shock lifetime of the GZ/YSZ double layered TBCs. The as sprayed TBCs were characterized using SEM, XRD and porosity measurements. Thermal diffusivity measurements were made using laser flash analysis and the thermal conductivity of the TBCs was calculated. The double layered TBC with the lowest YSZ (400GZ/100YSZ) thickness showed lower thermal diffusivity and thermal conductivity. The double layered TBCs were subjected to thermal shock test at a TBC surface temperature of 1350 °C. Results indicate that the TBC with a higher YSZ thickness (100GZ/400YSZ) showed inferior thermal shock lifetime whereas the TBCs with low YSZ thickness showed comparatively higher thermal shock lifetimes. Failure of the TBCs after thermal shock test was analyzed using SEM and XRD to gain further insights.

Place, publisher, year, edition, pages
Elsevier, 2019
Keywords
Gadolinium; Plasma jets; Plasma spraying; Thermal conductivity; Thermal shock; X ray diffraction; Yttria stabilized zirconia; Yttrium oxide; Zirconia, Diffusivity measurements; Double layered; Gadolinium zirconate; Layer thickness; Porosity measurement; Surface temperatures; Suspension plasma sprays; Thermal barrier coating (TBC), Thermal barrier coatings
National Category
Manufacturing, Surface and Joining Technology
Research subject
ENGINEERING, Manufacturing and materials engineering; Production Technology
Identifiers
urn:nbn:se:hv:diva-13106 (URN)10.1016/j.surfcoat.2018.10.046 (DOI)000455691100067 ()2-s2.0-85055204877 (Scopus ID)
Funder
Knowledge Foundation, 20140130
Available from: 2018-11-07 Created: 2018-11-07 Last updated: 2019-02-04Bibliographically approved
Mahade, S., Zhou, D., Curry, N., Markocsan, N., Nylén, P. & Vassen, R. (2019). Tailored microstructures of gadolinium zirconate/YSZ multi-layered thermal barrier coatings produced by suspension plasma spray: Durability and erosion testing. Journal of Materials Processing Technology, 264, 283-294
Open this publication in new window or tab >>Tailored microstructures of gadolinium zirconate/YSZ multi-layered thermal barrier coatings produced by suspension plasma spray: Durability and erosion testing
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2019 (English)In: Journal of Materials Processing Technology, ISSN 0924-0136, E-ISSN 1873-4774, Vol. 264, p. 283-294Article in journal (Refereed) Published
Abstract [en]

This work employed an axial suspension plasma spray (SPS) process to deposit two different gadolinium zirconate (GZ) based triple layered thermal barrier coatings (TBCs). The first was a 'layered' TBC (GZ dense/GZ/YSZ) where the base layer was YSZ, intermediate layer was a relatively porous GZ and the top layer was a relatively dense GZ. The second triple layered TBC was a 'composite' TBC (GZ dense/GZ + YSZ/YSZ) comprising of an YSZ base layer, a GZ + YSZ intermediate layer and a dense GZ top layer. The as sprayed TBCs (layered and composite) were characterized using SEM/EDS and XRD. Two different methods (water intrusion and image analysis) were used to measure the porosity content of the as sprayed TBCs. Fracture toughness measurements were made on the intermediate layers (GZ + YSZ layer of the composite TBC and porous GZ layer of the layered TBC respectively) using micro indentation tests. The GZ + YSZ layer in the composite TBC was shown to have a slightly higher fracture toughness than the relatively porous GZ layer in the layered TBC. Erosion performance of the as sprayed TBCs was evaluated at room temperature where the composite TBC showed higher erosion resistance than the layered TBC. However, in the burner rig test conducted at 1400 °C, the layered TBC showed higher thermal cyclic lifetime than the composite TBC. Failure analysis of the thermally cycled and eroded TBCs was performed using SEM and XRD. © 2018 Elsevier B.V.

Place, publisher, year, edition, pages
Elsevier, 2019
Keywords
Composite materials, Durability, Erosion, Failure (mechanical), Gadolinium, Plasma jets, Plasma spraying, Thermal barrier coatings, X ray diffraction, Yttria stabilized zirconia, Burner rig, Erosion resistance, Fracture toughness measurements, Gadolinium zirconate, Intermediate layers, Micro-indentation tests, Suspension plasma sprays, Thermal barrier coating (TBCs), Fracture toughness
National Category
Manufacturing, Surface and Joining Technology
Research subject
ENGINEERING, Manufacturing and materials engineering; Production Technology
Identifiers
urn:nbn:se:hv:diva-13041 (URN)10.1016/j.jmatprotec.2018.09.016 (DOI)000450135400028 ()2-s2.0-85053777782 (Scopus ID)
Funder
Knowledge Foundation, 20140130
Available from: 2018-10-29 Created: 2018-10-29 Last updated: 2018-12-20Bibliographically approved
Mahade, S., Ruelle, C., Curry, N., Holmberg, J., Björklund, S., Markocsan, N. & Nylén, P. (2019). Understanding the effect of material composition and microstructural design on the erosion behavior of plasma sprayed thermal barrier coatings. Applied Surface Science, 488, 170-184
Open this publication in new window or tab >>Understanding the effect of material composition and microstructural design on the erosion behavior of plasma sprayed thermal barrier coatings
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2019 (English)In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 488, p. 170-184Article in journal (Refereed) Published
Abstract [en]

In this work, three different TBC compositions comprising of yttria partially stabilized zirconia (8YSZ), yttria fully stabilized zirconia (48YSZ) and gadolinium zirconate (GZ) respectively, were processed by suspension plasma spray (SPS) to obtain columnar microstructured TBCs. Additionally, for comparison, lamellar microstructured, 7YSZ TBC was deposited by air plasma spray (APS) process. SEM analysis was carried out to investigate the microstructure and white light interferometry was used to evaluate the surface morphology of the as-sprayed TBCs. Porosity measurements were made using water intrusion and image analysis methods and it was observed that the SPS-YSZ and APS-YSZ TBCs showed higher porosity content than SPS-GZ and SPS-48YSZ. The as-sprayed TBC variations (APS-YSZ, SPS-YSZ, SPS-GZ, and SPS-48YSZ) were subjected to erosion test. Results indicate that the erosion resistance of APS-YSZ TBC was inferior to the SPS-YSZ, SPS-GZ and SPS-48YSZ TBCs respectively. Among the SPS processed TBCs, SPS-YSZ showed the highest erosion resistance whereas the SPS-48YSZ showed the lowest erosion resistance. SEM analysis of the eroded TBCs (cross section and surface morphology) was performed to gain further insights on their erosion behavior. Based on the erosion results and post erosion SEM analysis, erosion mechanisms for splat like microstructured APS TBC and columnar microstructured SPS TBCs were proposed. The findings from this work provide new insights on the erosion mechanisms of columnar microstructured TBCs and lamellar microstructured TBCs deposited by plasma spray. © 2019 Elsevier B.V.

Keywords
Erosion; Microstructure; Morphology; Plasma jets; Porosity; Sprayed coatings; Surface morphology; Thermal barrier coatings; Yttria stabilized zirconia; Yttrium oxide; Zirconia, Atmospheric plasma spray; Gadolinium zirconate; Stabilized zirconia; Suspension plasma sprays; Yttria partially stabilized zirconia, Plasma spraying
National Category
Manufacturing, Surface and Joining Technology
Research subject
ENGINEERING, Manufacturing and materials engineering
Identifiers
urn:nbn:se:hv:diva-13987 (URN)10.1016/j.apsusc.2019.05.245 (DOI)2-s2.0-85066427612 (Scopus ID)
Funder
Knowledge Foundation, 20140130
Available from: 2019-06-20 Created: 2019-06-20 Last updated: 2019-07-25Bibliographically approved
Balachandramurthi Ramanathan, A., Moverare, J., Mahade, S. & Pederson, R. (2018). Additive Manufacturing of Alloy 718 via Electron Beam Melting: Effect of Post-Treatment on the Microstructure and the Mechanical Properties.. Materials, 12(1), Article ID E68.
Open this publication in new window or tab >>Additive Manufacturing of Alloy 718 via Electron Beam Melting: Effect of Post-Treatment on the Microstructure and the Mechanical Properties.
2018 (English)In: Materials, ISSN 1996-1944, E-ISSN 1996-1944, Vol. 12, no 1, article id E68Article in journal (Refereed) Published
Abstract [en]

Alloy 718 finds application in gas turbine engine components, such as turbine disks, compressor blades and so forth, due to its excellent mechanical and corrosion properties at elevated temperatures. Electron beam melting (EBM) is a recent addition to the list of additive manufacturing processes and has shown the capability to produce components with unique microstructural features. In this work, Alloy 718 specimens were manufactured using the EBM process with a single batch of virgin plasma atomized powder. One set of as-built specimens was subjected to solution treatment and ageing (STA); another set of as-built specimens was subjected to hot isostatic pressing (HIP), followed by STA (and referred to as HIP+STA). Microstructural analysis of as-built specimens, STA specimens and HIP+STA specimens was carried out using optical microscopy and scanning electron microscopy. Typical columnar microstructure, which is a characteristic of the EBM manufactured alloy, was observed. Hardness evaluation of the as-built, STA and HIP+STA specimens showed that the post-treatments led to an increase in hardness in the range of ~50 HV1. Tensile properties of the three material conditions (as-built, STA and HIP+STA) were evaluated. Post-treatments lead to an increase in the yield strength (YS) and the ultimate tensile strength (UTS). HIP+STA led to improved elongation compared to STA due to the closure of defects but YS and UTS were comparable for the two post-treatment conditions. Fractographic analysis of the tensile tested specimens showed that the closure of shrinkage porosity and the partial healing of lack of fusion (LoF) defects were responsible for improved properties. Fatigue properties were evaluated in both STA and HIP+STA conditions. In addition, three surface conditions were also investigated, namely the 'raw' as-built surface, the machined surface with the contour region and the machined surface without the contour region. Machining off the contour region completely together with HIP+STA led to significant improvement in fatigue performance.

Keywords
Alloy 718, electron beam melting, fatigue properties, microstructure, tensile properties, texture
National Category
Manufacturing, Surface and Joining Technology
Research subject
ENGINEERING, Manufacturing and materials engineering; Production Technology
Identifiers
urn:nbn:se:hv:diva-13364 (URN)10.3390/ma12010068 (DOI)000456410200068 ()30585242 (PubMedID)2-s2.0-85059182911 (Scopus ID)
Funder
Knowledge Foundation, 20160281
Available from: 2019-01-08 Created: 2019-01-08 Last updated: 2019-05-27Bibliographically approved
Mahade, S. (2018). Functional Performance of Gadolinium Zirconate/Yttria Stabilized Zirconia Multi-Layered Thermal Barrier Coatings. (Doctoral dissertation). Trollhättan: University West
Open this publication in new window or tab >>Functional Performance of Gadolinium Zirconate/Yttria Stabilized Zirconia Multi-Layered Thermal Barrier Coatings
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Yttria stabilized zirconia (YSZ) is the state-of-the-art ceramic top coat material used for thermal barrier coating (TBC) applications. Demand for higher efficiency in gas turbine engines has led to a continuous increase in the gas in let temperature. However, this increase in temperature has pushed YSZ to its upper limit. Above1200 °C, issues such as poor phase stability, high sintering rate, and susceptibility to CMAS (Calcium Magnesium Alumino Silicates) degradation limit the durability of YSZ based TBCs. Among the new top coat materials suggested for high temperature TBC applications, gadolinium zirconate (GZ) is an interesting alternative to YSZ since it has shown attractive properties which include a better resistance to CMAS attack. However, GZ has poor thermo-chemical compatibility with the thermally grown oxide (alumina), leading to poor thermalcyclic fatigue performance of single layered GZ TBCs. Therefore, a multi-layered GZ/YSZ based TBC design seems promising. This work presents a new approach of depositing multi-layered (double and triple layered) GZ/YSZ TBCs using the recently developed suspension plasma spray(SPS) process. SPS was employed in this work because of its capability to mimic the electron beam physical vapour deposition (EB-PVD) process in terms of producing columnar microstructured TBCs. Single layer YSZ TBCs were also deposited by SPS process and used as a reference for comparing the functional performance of multi-layered GZ based TBCs. The primary aim of this work was to improve the durability of GZ based multilayered TBCs at high temperatures. Durability tests were performed in the temperature range 1100 °C - 1400 °C under different thermal cyclic test conditions (with and without thermal gradient). The results indicate that multilayered GZ based TBCs improve durability compared to the single layer YSZTBCs at all the test temperatures. Failure analysis of the multi-layered GZ/YSZTBCs revealed spallation within the GZ layer close to GZ/YSZ interface and the reason was believed to be the inferior fracture toughness of GZ. In order to improve the fracture toughness in the region of failure, a composite approach comprising multi-layered GZ+YSZ based TBC was considered. It was shown that the composite GZ+YSZ based TBCs did not improve the thermal cyclic lifetime, although improvement in fracture toughness was observed. As a further extension of this work, the influence of YSZ layer thickness on the durability of GZ/YSZTBCs was investigated. It was shown that an increase in YSZ layer thickness in the GZ/YSZ TBC led to poor durability. Additionally, the other important performance criteria for TBCs, i.e. thermal conductivity, was measured experimentally and compared with the single layer YSZ TBC. It was shown that the GZ based TBCs had lower thermal conductivity than YSZ. The second aim was to investigate and compare the erosion performance of multi-layered GZ based TBCs and single layered YSZ TBCs. In the erosion testconducted at room temperature, the GZ based TBCs showed lower erosion resistance compared to the single layer YSZ TBC. The main reason for this difference was attributed to the inferior fracture toughness of GZ. In case of the composite multi-layered GZ+YSZ based TBC, an improvement in erosion resistance was observed compared to the multi-layered GZ based TBC. Based on the results obtained, this work has demonstrated that SPS is a promising processing technique to produce columnar microstructured TBCs irrespective of the composition (GZ, YSZ, GZ+YSZ). It was also shown that GZ/YSZ multilayered TBCs are promising for high temperature TBC applications due to theirl ow thermal conductivity and high thermal cyclic fatigue lifetime. However, low erosion resistance for certain applications might be an issue for the GZ basedTBCs.

Place, publisher, year, edition, pages
Trollhättan: University West, 2018. p. 82
Series
PhD Thesis: University West ; 18
Keywords
Composite; 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-12301 (URN)978-91-87531-86-6 (ISBN)978-91-87531-85-9 (ISBN)
Public defence
2018-06-05, F104, Trollhättan, 10:15 (English)
Opponent
Supervisors
Available from: 2018-05-16 Created: 2018-05-15 Last updated: 2018-05-16Bibliographically approved
Mahade, S., Zhou, D. & Vassen, R. (2017). Effect of spray parameters on the microstructure and porosity content of gadolinium zirconate TBCs deposited by suspension plasma spray. In: Proceedings of the International Thermal Spray Conference & Exposition (ITSC 2017): . Paper presented at International Thermal Spray Conference and Exposition 2017, ITSC 2017, June 7-9, 2017, Düsseldorf, Germany (pp. 31-35). New York: Curran Associates, Inc, Article ID DVS336.
Open this publication in new window or tab >>Effect of spray parameters on the microstructure and porosity content of gadolinium zirconate TBCs deposited by suspension plasma spray
2017 (English)In: Proceedings of the International Thermal Spray Conference & Exposition (ITSC 2017), New York: Curran Associates, Inc , 2017, p. 31-35, article id DVS336Conference paper, Published paper (Refereed)
Abstract [en]

Gadolinium zirconate (GZ) is considered as a promising top coat candidate for high temperature(>1200°C) thermal barrier coating (TBC) applications. Suspension plasma spray (SPS) technique has shown the capability to generate a wide range of microstructures which includes the more desirable columnar microstructure. In this study, GZ single layer TBCs were deposited by axial SPS process. The variable parameters include the standoff distance, solid load content of the suspension and input power. The cross section and top surface of the as sprayed TBCs were analyzed by SEM. The phase content in the as sprayed TBCs was analyzed by XRD. The porosity content of the as sprayed TBCs was measured using image analysis. In the SEM analysis, it was observed that a lower solid load content in the suspension favoured the formation of a columnar microstructure. Additionally, at lower solid load content, increase in standoff distance resulted in columnar microstructure with high porosity content in the TBC. However,with higher solid content suspension and alteration of input power, only adense vertical cracked microstructure can be obtained.                 

Place, publisher, year, edition, pages
New York: Curran Associates, Inc, 2017
Keywords
Plasma spray, parameters, top coat
National Category
Manufacturing, Surface and Joining Technology
Research subject
ENGINEERING, Manufacturing and materials engineering; Production Technology
Identifiers
urn:nbn:se:hv:diva-11924 (URN)2-s2.0-85047508163 (Scopus ID)9781510858220 (ISBN)
Conference
International Thermal Spray Conference and Exposition 2017, ITSC 2017, June 7-9, 2017, Düsseldorf, Germany
Available from: 2017-12-14 Created: 2017-12-14 Last updated: 2019-01-29Bibliographically approved
Mahade, S., Jonnalagadda, K. P., Curry, N., Li, X.-H., Björklund, S., Markocsan, N., . . . Peng, R. L. (2017). Engineered architectures of gadolinium zirconate based thermal barrier coatings subjected to hot corrosion test. Surface & Coatings Technology, 328, 361-370
Open this publication in new window or tab >>Engineered architectures of gadolinium zirconate based thermal barrier coatings subjected to hot corrosion test
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2017 (English)In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 328, p. 361-370Article in journal (Refereed) Published
Abstract [en]

Abstract Gadolinium zirconate (GZ) is considered as a promising top coat candidate for high temperature TBC applications. Suspension plasma spray has shown the capability to generate a wide range of microstructures including the desirable columnar microstructure. In this study, two different TBC architectures were deposited using the axial suspension plasma spray. The first variation was a triple layered TBC comprising of thin YSZ base layer beneath a relatively porous GZ intermediate layer and a dense GZ top layer. The second variation was a composite TBC architecture of GZ and YSZ comprising of thin YSZ base layer and GZ + YSZ top layer. Cross sectional SEM analysis of the layered and composite TBCs revealed a columnar microstructure. The porosity content of the deposited TBCs was measured using two methods (Image Analysis and Water Intrusion). The as-sprayed TBCs were exposed at 900 °C for 8 h to a corrosive salt environment consisting of a mixture of vanadium pentoxide and sodium sulfate. XRD analysis on the as-corroded TBCs top surface showed the presence of gadolinium vanadate in both the layered and the composite TBCs. SEM/EDS analysis of the top surface and the cross-section of the layered and composite TBCs after hot corrosion test revealed the infiltration of the molten salts through the columnar gaps. The composite TBC showed a lower hot corrosion induced damage compared to the layered TBC where a considerable spallation was observed.

Keywords
Gadolinium zirconate, Hot corrosion, Suspension plasma spray, Columnar microstructure
National Category
Manufacturing, Surface and Joining Technology
Research subject
ENGINEERING, Manufacturing and materials engineering
Identifiers
urn:nbn:se:hv:diva-11588 (URN)10.1016/j.surfcoat.2017.09.005 (DOI)000413376900040 ()2-s2.0-85028920767 (Scopus ID)
Funder
Knowledge Foundation, 20140130
Available from: 2017-09-20 Created: 2017-09-20 Last updated: 2019-02-05Bibliographically approved
Mahade, S., Curry, N., Björklund, S., Markocsan, N. & Nylén, P. (2017). Engineered thermal barrier coatings deposited by suspension plasma spray. Materials letters (General ed.), 209, 517-521
Open this publication in new window or tab >>Engineered thermal barrier coatings deposited by suspension plasma spray
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2017 (English)In: Materials letters (General ed.), ISSN 0167-577X, E-ISSN 1873-4979, Vol. 209, p. 517-521Article in journal (Refereed) Published
Abstract [en]

Yttria stabilized zirconia (YSZ) is susceptible to CMAS (Calcium Magnesium Alumino Silicates) attack at high temperatures (>1200 °C) which limits its durability. New ceramic materials which can overcome these high temperature challenges are highly desirable. This work investigates the feasibility of depositing two variations of three ceramic layered thermal barrier coatings. The first variation comprised of yttria as the top ceramic layer with gadolinium zirconate (GZ) as the intermediate layer and YSZ as the base layer. The second variation comprised of Yttrium Aluminum Garnet (YAG) as the top layer with gadolinium zirconate as the intermediate layer and YSZ as the base layer. Microstructural analysis of the as sprayed three layered TBCs were performed by SEM/EDS. Columnar microstructures with a relatively dense top layer were obtained in both the variations. The porosity content of the TBCs was measured by water intrusion and image analysis methods. Phase composition of each layer of the as sprayed TBCs was analyzed using XRD. YAG showed an amorphous phase whereas GZ showed a cubic defect fluorite phase and tetragonal phase was observed in YSZ. In the case of yttria, monoclinic and cubic phases were observed. © 2017 Elsevier B.V.

Keywords
Aluminum; Ceramic materials; Coatings; Gadolinium; Garnets; Plasma jets; Plasma spraying; Silicates; Thermal barrier coatings; Yttrium; Yttrium oxide; Zirconia, Columnar microstructures; Gadolinium zirconate; Image analysis method; Intermediate layers; Microstructural analysis; Suspension plasma sprays; Yttria-stabilized zirconias (YSZ); Yttrium aluminum garnet, Yttria stabilized zirconia
National Category
Manufacturing, Surface and Joining Technology
Research subject
ENGINEERING, Manufacturing and materials engineering
Identifiers
urn:nbn:se:hv:diva-11613 (URN)10.1016/j.matlet.2017.08.096 (DOI)000413124300131 ()2-s2.0-85028409787 (Scopus ID)
Funder
Knowledge Foundation, 20140130
Available from: 2017-09-21 Created: 2017-09-21 Last updated: 2019-05-23Bibliographically approved
Mahade, S., Curry, N., Björklund, S., Markocsan, N., Nylén, P. & Vaßen, R. (2017). Erosion Performance of Gadolinium Zirconate-Based Thermal Barrier Coatings Processed by Suspension Plasma Spray. Journal of thermal spray technology (Print), 26(1-2), 108-115
Open this publication in new window or tab >>Erosion Performance of Gadolinium Zirconate-Based Thermal Barrier Coatings Processed by Suspension Plasma Spray
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2017 (English)In: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 26, no 1-2, p. 108-115Article in journal (Refereed) Published
Abstract [en]

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 triple-layer 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 as-sprayed TBCs was carried out using XRD (x-ray diffraction) where a tetragonal prime phase of zirconia in the 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 microstructureerosion, test gadolinium, zirconatemulti-layered thermal barrier, coating, suspension plasma spray, yttria-stabilized zirconia
National Category
Manufacturing, Surface and Joining Technology
Research subject
Production Technology
Identifiers
urn:nbn:se:hv:diva-10498 (URN)10.1007/s11666-016-0479-4 (DOI)000392060300011 ()2-s2.0-85001975445 (Scopus ID)
Funder
Knowledge Foundation, 20140130
Note

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.

Available from: 2017-01-09 Created: 2017-01-09 Last updated: 2019-01-29Bibliographically approved
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ORCID iD: ORCID iD iconorcid.org/0000-0003-2475-9284

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