Issue 35

K. Slámečka et alii, Frattura ed Integrità Strutturale, 35 (2016) 322-329; DOI: 10.3221/IGF-ESIS.35.37 322 Focussed on Crack Paths Plasma-sprayed thermal barrier coatings: numerical study on damage localization and evolution K. Slámečka, P. Skalka, L. Čelko, J. Pokluda Brno University of Technology, Central European Institute of Technology, Technická 10, 616 69 Brno, Czech Republic k.slamecka@ceitec.vutbr.cz, p.skalka@ceitec.vutbr.cz , l.celko@ceitec.vutbr.cz , j.pokluda@ceitec.vutbr.cz L. Saucedo-Mora, T. J. Marrow University of Oxford, Department of Materials, Parks Road, Oxford OX1 3PH, UK luis.saucedomora@materials.ox.ac.uk , james.marrow@materials.ox.ac.uk U. Thandavamoorthy Ecole des Mines de Nantes, 4 Rue Alfred Kastler, 44300 Nantes, France t_uma@hotmail.fr A BSTRACT . Thermal barrier coatings (TBCs) are advanced material systems used to enhance performance and in-service life of components operated at high temperatures in gas turbines and other power-generation devices. Because of complexity, numerical methods became important tools both for design of these coatings and for in-service life estimations and optimization. In this contribution, two main features that affect the TBCs’ performance, namely the roughness of the bond coat and the microstructure of the ceramic top coat, are discussed based on Finite Element Method (FEM) and Finite Element Microstructure MEshfree (FEMME) simulations that were used to calculate stresses and assess damage within the coating. Roughness data obtained from plasma-sprayed CoNiCrAlY + YSZ coated samples are supplemented to discuss assumptions and results of employed numerical models. K EYWORDS . Thermal barrier coatings; Plasma spraying; Finite element modelling; Multi-scale numerical model; Roughness. I NTRODUCTION hermal barrier coatings (TBCs) are advanced material systems used to enhance performance and in-service life of components operated at high temperatures in gas turbines and other power-generation devices [1]. TBCs usually consist of two applied layers: (i) an aluminium-rich metallic bond coat (BC), and (ii) an yttria-stabilized zirconia (YSZ) insulating ceramic top coat (TC), Fig. 1. The third thin oxide layer (the so-called thermally grown oxide – TGO) gradually develops at high temperatures at the TC/BC interface, thus resulting in a three-layer system. The main failure mode of TBCs is spallation of the top coat resulting from damage accumulated at or near the TC/BC interface that is followed by rapid deterioration of properties of the bond coat and the load-bearing superalloy substrate. In the case of TBCs prepared by plasma spraying, coating spallation is due to propagation and coalescence of cracks that are nucleated at T