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Jonnalagadda, Krisha Praveen
Publications (7 of 7) Show all publications
Jonnalagadda, K. P., Eriksson, R., Yuan, K., Li, X.-H., Ji, X., Yu, Y. & Peng, R. L. (2017). A Study of Damage Evolution in High Purity Nano TBCs During Thermal Cycling: A Fracture Mechanics Based modeling approach.. In: ASME Turbine Expo: . Paper presented at ASME Turbine Expo 2017, June 25-29, 2017, North Carolina, USA (pp. 2889-2899). Elsevier, 37, Article ID 8.
Open this publication in new window or tab >>A Study of Damage Evolution in High Purity Nano TBCs During Thermal Cycling: A Fracture Mechanics Based modeling approach.
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2017 (English)In: ASME Turbine Expo, Elsevier, 2017, Vol. 37, p. 2889-2899, article id 8Conference paper, Published paper (Refereed)
Abstract [en]

This work concerns the study of damage evolution in a newly developed high purity nano 8YSZ thermal barrier coating during thermal cyclic fatigue tests (TCF). TCF tests were conducted between 100 °C–1100 °C with a hold time of 1 h at 1100 °C, first till failure and later for interrupted tests. Cross section analysis along the diameter of the interrupted test samples revealed a mixed-type failure and that the most of the damage occurred towards the end of the coating’s life. To understand the most likely crack growth mechanism leading to failure, different crack growth paths have been modelled using finite element analysis. Crack growing from an existing defect in the top coat towards the top coat/TGO interface has been identified as the most likely mechanism. Estimated damage by the model could predict the rapid increase in the damage towards the end of the coating’s life.

Place, publisher, year, edition, pages
Elsevier, 2017
Keywords
Thermal cyclic fatigue, High purity nano YSZ, Crack growth modelling, Damage evolution
National Category
Materials Engineering
Identifiers
urn:nbn:se:liu:diva-142310 (URN)10.1016/j.jeurceramsoc.2017.02.054 (DOI)2-s2.0-85014154522 (Scopus ID)
Conference
ASME Turbine Expo 2017, June 25-29, 2017, North Carolina, USA
Available from: 2017-10-25 Created: 2017-10-25 Last updated: 2017-11-21Bibliographically approved
Eriksson, R., Chen, Z. & Jonnalagadda, K. P. (2017). Bending Fatigue of Thermal Barrier Coatings. Journal of engineering for gas turbines and power, 139(12), 122101-1-122101-6
Open this publication in new window or tab >>Bending Fatigue of Thermal Barrier Coatings
2017 (English)In: Journal of engineering for gas turbines and power, ISSN 0742-4795, E-ISSN 1528-8919, Vol. 139, no 12, p. 122101-1-122101-6Article in journal (Refereed) Published
Abstract [en]

Thermal barrier coatings (TBCs) are ceramic coatings used in gas turbines to lower the base metal temperature. During operation, the TBC may fail through, for example, fatigue. In this study, a TBC system deposited on a Ni-base alloy was tested in tensile bending fatigue. The TBC system was tested as-sprayed and oxidized, and two load levels were used. After interrupting the tests, at 10,000–50,000 cycles, the TBC tested at the lower load had extensive delamination damage, whereas the TBC tested at the higher load was relatively undamaged. At the higher load, the TBC formed vertical cracks which relieved the stresses in the TBC and retarded delamination damage. A finite element (FE) analysis was used to establish a likely vertical crack configuration (spacing and depth), and it could be confirmed that the corresponding stress drop in the TBC should prohibit delamination damage at the higher load.

Place, publisher, year, edition, pages
ASME Press, 2017
National Category
Materials Engineering
Identifiers
urn:nbn:se:liu:diva-142274 (URN)10.1115/1.4037587 (DOI)000415791400010 ()2-s2.0-85029559590 (Scopus ID)
Available from: 2017-10-24 Created: 2017-10-24 Last updated: 2017-12-12Bibliographically approved
Jonnalagadda, K. P., Eriksson, R., Yuan, K., Li, X.-H., Ji, X., Yu, Y. & Peng, R. L. (2017). Comparison of Damage Evolution During Thermal Cycling in a High Purity Nano and Conventional Thermal Barrier Coating. Surface & Coatings Technology, 332, 47-56
Open this publication in new window or tab >>Comparison of Damage Evolution During Thermal Cycling in a High Purity Nano and Conventional Thermal Barrier Coating
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2017 (English)In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 332, p. 47-56Article in journal (Refereed) Published
Abstract [en]

Thermal barrier coatings (TBCs), consisting of a ceramic top coat and a metallic bond coat, offer resistance against high temperature degradation of turbine components. Cyclic oxidation of the bond coat, thermal stresses due to their thermal mismatches during cyclic operations, and sintering of the top coat are considered to be the common ways by which thermal barrier coatings fail. To reduce sintering, a nano structured high purity yttria stabilized zirconia (YSZ) was developed. The focus of this work is to compare the damage development of such high purity nano YSZ TBC during thermal cycling with a conventional YSZ TBC. Thermal cyclic fatigue (TCF) tests were conducted on both the TBC systems between 100 °C and 1100 °C with a 1 h hold time at 1100 °C. TCF test results showed that conventional YSZ TBC exhibited much higher life compared to the high purity nano YSZ TBC. The difference in the lifetime is explained by the use of microstructural investigations, crack length measurements along the cross-section and the difference in the elastic modulus. Furthermore, stress intensity factors were calculated in order to understand the difference(s) in the damage development between the two TBC systems.

Place, publisher, year, edition, pages
Elsevier, 2017
Keywords
High purity nano, damage evolution, thermal cycling fatigue, crack length measurement, conventional TBC
National Category
Materials Engineering
Identifiers
urn:nbn:se:liu:diva-142311 (URN)10.1016/j.surfcoat.2017.09.069 (DOI)000418968100007 ()2-s2.0-85030751243 (Scopus ID)
Note

Funding agencies: Vinnova in Sweden [2015-06870]

Available from: 2017-10-25 Created: 2017-10-25 Last updated: 2018-01-12Bibliographically approved
Jonnalagadda, K. P., Li, X.-H. & Peng, R. L. (2017). Corrosion Mechanism in Thermal Barrier Coatings During Exposure to a Gas Mixture of N2-CO-CO2-SO2. In: : . Paper presented at EUROMAT17, Thessaloniki 17-21 September 2017,Greece (pp. 1-1).
Open this publication in new window or tab >>Corrosion Mechanism in Thermal Barrier Coatings During Exposure to a Gas Mixture of N2-CO-CO2-SO2
2017 (English)Conference paper, Oral presentation with published abstract (Refereed)
Keywords
high temperature corrosion, mixed gas corrosion, thermal barrier coatings, Amdry 964
National Category
Materials Engineering
Identifiers
urn:nbn:se:liu:diva-143977 (URN)
Conference
EUROMAT17, Thessaloniki 17-21 September 2017,Greece
Available from: 2018-01-01 Created: 2018-01-01 Last updated: 2018-01-16Bibliographically approved
Mahade, S., Jonnalagadda, K. P., Curry, N., Li, X.-H., Bjorklund, S., Markocsan, N., . . . Peng, R. (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]

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 degrees 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. (C) 2017 Elsevier B.V. All rights reserved.

Place, publisher, year, edition, pages
Elsevier, 2017
Keywords
Gadolinium zirconate; Hot corrosion; Suspension plasma spray; Columnar microstructure
National Category
Manufacturing, Surface and Joining Technology
Identifiers
urn:nbn:se:liu:diva-142965 (URN)10.1016/j.surfcoat.2017.09.005 (DOI)000413376900040 ()2-s2.0-85028920767 (Scopus ID)
Note

Funding Agencies|KK Foundation, Sweden [Dnr: 20140130]; AForsk foundation, Sweden [16-799]

Available from: 2017-11-13 Created: 2017-11-13 Last updated: 2017-11-29Bibliographically approved
Jonnalagadda, K. P., Yuan, K., Li, X.-H., Peng, R. L. & Yu, Y. (2017). Modeling the Diffusion of Minor Elements in Different MCrAlY-Superalloy Coating/Substrates at High Temperature. In: The Minerals, Metals & Materials Series.: . Paper presented at TMS Conference. Energy Materials, San Diego, USA, 27 February - 3 March, 2017.
Open this publication in new window or tab >>Modeling the Diffusion of Minor Elements in Different MCrAlY-Superalloy Coating/Substrates at High Temperature
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2017 (English)In: The Minerals, Metals & Materials Series., 2017Conference paper, Published paper (Refereed)
National Category
Materials Engineering
Identifiers
urn:nbn:se:liu:diva-142312 (URN)
Conference
TMS Conference. Energy Materials, San Diego, USA, 27 February - 3 March, 2017
Available from: 2017-10-25 Created: 2017-10-25 Last updated: 2017-11-21Bibliographically approved
Eriksson, R., Gupta, M., Broitman, E., Jonnalagadda, K. P., Nylén, P. & Peng, R. (2015). Stresses and Cracking During Chromia-Spinel- NiO Cluster Formation in TBC Systems. Journal of thermal spray technology (Print), 24(6), 1002-1014
Open this publication in new window or tab >>Stresses and Cracking During Chromia-Spinel- NiO Cluster Formation in TBC Systems
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2015 (English)In: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 24, no 6, p. 1002-1014Article in journal (Refereed) Published
Abstract [en]

Thermal barrier coatings (TBC) are used in gas turbines to reduce the temperatures in the underlying substrate. There are several mechanisms that may cause the TBC to fail; one of them is cracking in the coating interface due to extensive oxidation. In the present study, the role of so called chromia-spinel-NiO (CSN) clusters in TBC failure was studied. Such clusters have previously been found to be prone to cracking. Finite element modeling was performed on a CSN cluster to find out at which stage of its formation it cracks and what the driving mechanisms of cracking are. The geometry of a cluster was obtained from micrographs and modeled as close as possible. Nanoindentation was performed on the cluster to get the correct Young’s moduli. The volumetric expansion associated with the formation of NiO was also included. It was found that the cracking of the CSN clusters is likely to occur during its last stage of formation as the last Ni-rich core oxidizes. Furthermore, it was shown that the volumetric expansion associated with the oxidation only plays a minor role and that the main reason for cracking is the high coefficient of thermal expansion of NiO.

Place, publisher, year, edition, pages
Springer, 2015
Keywords
chromia-spinel-NiO, failure mechnism, finite element modeling, oxide cluster, thermal barrier coating
National Category
Other Materials Engineering
Identifiers
urn:nbn:se:liu:diva-120423 (URN)10.1007/s11666-015-0270-y (DOI)000358965400012 ()
Available from: 2015-08-10 Created: 2015-08-10 Last updated: 2017-12-04
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