PSI - Issue 22

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Procedia Structural Integrity 22 (2019) 243–250

First International Symposium on Risk and Safety of Complex Structures and Components Modeling of interface failure in a thermal barrier coating system on Ni based superalloys Andrey Burov a , Elena Fedorova a,b ,* First International Symposium on Risk and Safety of Complex Structures and Components odeling of interface failure in a ther al barrier coating syste on i based superalloys Andrey Burov a , Elena Fedorova a,b ,*

a Institute of Computational Technologies SB RAS, Krasnoyarsk 660049, Russia b Polytechnic Institute, Siberian Federal University, Krasnoyarsk 660041, Russia a Institute of Computational Technologies SB RAS, Krasnoyarsk 660049, Russia b Polytechnic Institute, Siberian Federal University, Krasnoyarsk 660041, Russia

© 2019 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/) Peer-review under responsibility of the First International Symposium on Risk and Safety of Complex Structures and Components organizers observed in the latter case. Possible scenarios of the TBC failure in terms of further cracks propagation are discussed . © 2019 The Authors. Published by Elsevier B. .This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/) Peer-review under responsibility of the First International Sy posiu on Risk and Safety of Co plex Structures and Co ponents organizers Abstract In the present work, finite element modelling is employed to study interface cracking behaviour in a thermal barrier coating (TBC) on a single crystal Ni-based superalloy. The cohesive zone elements are implemented in the model to simulate interfacial debonding between the top-coat (TC), thermally grown oxide (TGO) and bond-coat (BC). To evaluate the effect of the interface geometry on the residual stress state and cracking behaviour, two periodic units of the TGO profile are analysed: a regular sinusoidal undulation with constant thickness and an irregular (unevenly thicker) TGO layer with symmetrical penetrations into the TC and BC layers. It has been found that the morphology of the TGO layer influences not only the magnitude and distribution of residual stresses but also governs the mechanisms of interfacial failure. For the regular TGO shape, the debonding cracks form at the peak of TGO/BC interface and at the valley of TC/TGO interface. Whereas only the TC/TGO interfacial debonding is observed in case of the irregular TGO profile. The debondings can induce the stress redistribution between the TBC layers that depends on which interface and to what extent is damaged. The TBC system with the regular TGO layer appears to be a more prone to interface failure than that one with the irregular TGO shape. However, much higher compressive stresses in the TGO layer are observed in the latter case. Possible scenarios of the TBC failure in terms of further cracks propagation are discussed . 2019 The Authors. Published by Elsevier B. .This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/) Peer-review under responsibility of the First International Sy posiu on Risk and Safety of Co plex Structures and Co ponents organizers 1. Introduction Thermal barrier coatings (TBC) deposited on superalloy substrates are widely used to protect the hot section structural components, such as aircraft gas turbine engines and industrial gas turbines, against oxidation and large thermal gradients during service life. The mechanisms controlling the durability and the damage evolution in TBC have been extensively studied over the past 30 years, as it is described by Evans A.G. et al. (2001), Pindera M.-J. et al. (2005), Hille T.S. et al. (2011). One of major causes for limiting the lifetime of the TBC systems is related to nucleation, propagation and coalescence of cracks along the material interfaces. Abstract In the present work, finite element modelling is employed to study interface cracking behaviour in a thermal barrier coating (TBC) on a single crystal Ni-based superalloy. The cohesive zone elements are implemented in the model to simulate interfacial debonding between the top-coat (TC), thermally grown oxide (TGO) and bond-coat (BC). To evaluate the effect of the interface geometry on the residual stress state and cracking behaviour, two periodic units of the TGO profile are analysed: a regular sinusoidal undulation with constant thickness and an irregular (unevenly thicker) TGO layer with symmetrical penetrations into the TC and BC layers. It has been found that the morphology of the TGO layer influences not only the magnitude and distribution of residual stresses but also governs the mechanisms of interfacial failure. For the regular TGO shape, the debonding cracks form at the peak of TGO/BC interface and at the valley of TC/TGO interface. Whereas only the TC/TGO interfacial debonding is observed in case of the irregular TGO profile. The debondings can induce the stress redistribution between the TBC layers that depends on which interface and to what extent is damaged. The TBC system with the regular TGO layer appears to be a more prone to interface failure than that one with the irregular TGO shape. However, much higher compressive stresses in the TGO layer are Keywords: Ni-based superalloy; TBC system; interface; FEM; delamination mechanisms Keywords: Ni-based superalloy; TBC system; interface; FEM; delamination mechanisms 1. Introduction Thermal barrier coatings (TBC) deposited on superalloy substrates are widely used to protect the hot section structural components, such as aircraft gas turbine engines and industrial gas turbines, against oxidation and large thermal gradients during service life. The mechanisms controlling the durability and the damage evolution in TBC have been extensively studied over the past 30 years, as it is described by Evans A.G. et al. (2001), Pindera M.-J. et al. (2005), Hille T.S. et al. (2011). One of major causes for limiting the lifetime of the TBC systems is related to nucleation, propagation and coalescence of cracks along the material interfaces.

* Corresponding author. Tel.: +7-913-532-74-55 E-mail address: efedorova@sfu-kras.ru * Corresponding author. Tel.: +7-913-532-74-55 E-mail address: efedorova@sfu-kras.ru

2452-3216 © 2019 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/) Peer-review under responsibility of the First International Symposium on Risk and Safety of Complex Structures and Components organizers 10.1016/j.prostr.2020.01.031 2452-3216 © 2019 The Authors. Published by Elsevier B.V.This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/) Peer-review statement: Peer-review under responsibility of the First International Symposium on Risk and Safety of Complex Structures and Components organizers 2452-3216 © 2019 The Authors. Published by Elsevier B.V.This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/) Peer-review statement: Peer-review under responsibility of the First International Symposium on Risk and Safety of Complex Structures and Components organizers