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Publications (10 of 23) Show all publications
Mahade, S., Curry, N., Björklund, S., Markocsan, N. & Joshi, S. V. (2019). Durability of Gadolinium Zirconate/YSZ Double-Layered Thermal Barrier Coatings under Different Thermal Cyclic Test Conditions. Materials, 12(14), Article ID E2238.
Open this publication in new window or tab >>Durability of Gadolinium Zirconate/YSZ Double-Layered Thermal Barrier Coatings under Different Thermal Cyclic Test Conditions
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2019 (English)In: Materials, ISSN 1996-1944, E-ISSN 1996-1944, Vol. 12, no 14, article id E2238Article in journal (Refereed) Published
Abstract [en]

Higher durability in thermal barrier coatings (TBCs) is constantly sought to enhance the service life of gas turbine engine components such as blades and vanes. In this study, three double layered gadolinium zirconate (GZ)-on-yttria stabilized zirconia (YSZ) TBC variants with varying individual layer thickness but identical total thickness produced by suspension plasma spray (SPS) process were evaluated. The objective was to investigate the role of YSZ layer thickness on the durability of GZ/YSZ double-layered TBCs under different thermal cyclic test conditions i.e., thermal cyclic fatigue (TCF) at 1100 °C and a burner rig test (BRT) at a surface temperature of 1400 °C, respectively. Microstructural characterization was performed using SEM (Scanning Electron Microscopy) and porosity content was measured using image analysis technique. Results reveal that the durability of double-layered TBCs decreased with YSZ thickness under both TCF and BRT test conditions. The TBCs were analyzed by SEM to investigate microstructural evolution as well as failure modes during TCF and BRT test conditions. It was observed that the failure modes varied with test conditions, with all the three double-layered TBC variants showing failure in the TGO (thermally grown oxide) during the TCF test and in the ceramic GZ top coat close to the GZ/YSZ interface during BRT. Furthermore, porosity analysis of the as-sprayed and TCF failed TBCs revealed differences in sintering behavior for GZ and YSZ. The findings from this work provide new insights into the mechanisms responsible for failure of SPS processed double-layered TBCs under different thermal cyclic test conditions.

Keywords
burner rig test, double-layered TBC, gadolinium zirconate, suspension plasma spray, thermal cyclic fatigue, yttria stabilized zirconia
National Category
Manufacturing, Surface and Joining Technology
Identifiers
urn:nbn:se:hv:diva-14438 (URN)10.3390/ma12142238 (DOI)000480454300026 ()31336713 (PubMedID)2-s2.0-85070469165 (Scopus ID)
Funder
Knowledge Foundation, Dnr-20140130
Available from: 2019-10-02 Created: 2019-10-02 Last updated: 2019-10-15
Mahade, S., Narayan, K., Govindarajan, S., Björklund, S., Curry, N. & Joshi, S. V. (2019). Exploiting Suspension Plasma Spraying to Deposit Wear-Resistant Carbide Coatings.. Materials, 12(15), Article ID E2344.
Open this publication in new window or tab >>Exploiting Suspension Plasma Spraying to Deposit Wear-Resistant Carbide Coatings.
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2019 (English)In: Materials, ISSN 1996-1944, E-ISSN 1996-1944, Vol. 12, no 15, article id E2344Article in journal (Refereed) Published
Abstract [en]

Titanium- and chromium-based carbides are attractive coating materials to impart wear resistance. Suspension plasma spraying (SPS) is a relatively new thermal spray process which has shown a facile ability to use sub-micron and nano-sized feedstock to deposit high-performance coatings. The specific novelty of this work lies in the processing of fine-sized titanium and chromium carbides (TiC and Cr3C2) in the form of aqueous suspensions to fabricate wear-resistant coatings by SPS. The resulting coatings were characterized by surface morphology, microstructure, phase constitution, and micro-hardness. The abrasive, erosive, and sliding wear performance of the SPS-processed TiC and Cr3C2 coatings was also evaluated. The results amply demonstrate that SPS is a promising route to manufacture superior wear-resistant carbide-based coatings with minimal in situ oxidation during their processing.

Keywords
chromium carbide, suspension plasma spray, titanium carbide, wear
National Category
Manufacturing, Surface and Joining Technology
Research subject
ENGINEERING, Manufacturing and materials engineering
Identifiers
urn:nbn:se:hv:diva-14437 (URN)10.3390/ma12152344 (DOI)000482576900005 ()31344804 (PubMedID)2-s2.0-85070407089 (Scopus ID)
Available from: 2019-10-02 Created: 2019-10-02 Last updated: 2019-10-15
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: 2019-10-02Bibliographically 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)000472476200020 ()2-s2.0-85066427612 (Scopus ID)
Funder
Knowledge Foundation, 20140130
Available from: 2019-06-20 Created: 2019-06-20 Last updated: 2019-10-18Bibliographically 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., Markocsan, N., Nylén, P. & Curry, N. (2018). Effect of YSZ thickness on the thermal cyclic fatigue performance of gadolinium zirconate/YSZ double layered TBCs. Paper presented at International Thermal Spray Conference, ITSC 2018; Orlando; United States; 7 May 2018 through 10 May 2018. Proceedings of the International Thermal Spray Conference, 79-83
Open this publication in new window or tab >>Effect of YSZ thickness on the thermal cyclic fatigue performance of gadolinium zirconate/YSZ double layered TBCs
2018 (English)In: Proceedings of the International Thermal Spray Conference, p. 79-83Article in journal (Refereed) Published
Abstract [en]

Thermal barrier coatings (TBCs) play a vital role in allowing the gas turbine engines to operate at high temperatures. With higher operating temperatures (>1200°C), the standard TBC material, 7-8wt. % Yttria Stabilized Zirconia (YSZ), is susceptible to CMAS (Calcium Magnesium Alumino Silicates) degradation and undesirable phase transformation. New TBC materials such as gadolinium zirconate (GZ) have shown to be capable of overcoming the challenges faced by YSZ. However, GZ has inferior fracture toughness relative to YSZ. In this work, three double layered TBC variations with different GZ and YSZ thickness respectively (400GZ/100YSZ, 250GZ/250YSZ and 100GZ/400GZ respectively, where the prefix numbers represent thickness in urn) were produced by suspension plasma spray (SPS) process. In all the three double layered TBC variations, the overall TBC thickness with GZ as the top layer and YSZ as the base layer was kept the same (500 urn). The objective was to investigate the influence of YSZ thickness on the thermal cyclic fatigue performance of GZ/YSZ double layered TBC. The as sprayed TBCs were characterized by SEM, XRD and porosity measurements and later subjected to thermal cyclic fatigue test at 1100°C. It was observed that the GZ/YSZ double layered TBC with lowest YSZ thickness (400GZ/100YSZ) showed higher thermal cyclic lifetime whereas the TBC with thicker YSZ layer (100GZ/400YSZ) showed lowest thermal cyclic fatigue lifetime. The failure analysis of the thermally cycled TBCs revealed similar failure modes, i.e. spallation of the top coat due to horizontal crack propagation within the thermally grown oxide (TGO). Furthermore, the ceramic top coats in all the three TBC variations after failure showed the widening of column gaps. © 2018 ASM International® All rights reserved.

Place, publisher, year, edition, pages
ASM International, 2018
Keywords
Failure modes; Fatigue testing; Fracture toughness; Gadolinium; Magnesium compounds; Plasma spraying; Silicates; Thermal barrier coatings; Thermal fatigue; Yttrium oxide; Zirconia, Gadolinium zirconate; Operating temperature; Porosity measurement; Suspension plasma sprays; Thermal barrier coating (TBCs); Thermal cyclic fatigue; Thermally grown oxide; Yttria-stabilized zirconias (YSZ), Yttria stabilized zirconia
National Category
Manufacturing, Surface and Joining Technology
Research subject
ENGINEERING, Manufacturing and materials engineering; Production Technology
Identifiers
urn:nbn:se:hv:diva-14481 (URN)2-s2.0-85068908628 (Scopus ID)
Conference
International Thermal Spray Conference, ITSC 2018; Orlando; United States; 7 May 2018 through 10 May 2018
Available from: 2019-10-02 Created: 2019-10-02 Last updated: 2019-10-28Bibliographically 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; ENGINEERING, Manufacturing and materials engineering
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: 2019-10-23Bibliographically 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
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0003-2475-9284

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