Materials Science and Engineering A 426 (2006) 121–127 Analysis of damage evolution in thick ceramic coatings Victor A. Shevchuk a,∗ , VadimV. Silberschmidt b a Pidstryhach Institute for Applied Problems of Mechanics and Mathematics, National Academy of Sciences of Ukraine, 3b Naukova, L’viv 79060, Ukraine b Wolfson School of Mechanical and Manufacturing Engineering, Loughborough University, Loughborough, Leicestershire LE11 3TU, UK Received 2 August 2005; received in revised form 21 December 2005; accepted 28 March 2006 Abstract This paper analyses the damage evolution process in thick ceramic coatings on cylindrical bodies exposed to uniform heating for two cases of the substrate material under conditions of plane strain. Alumina coatings with three different types of the initial through-thickness distribution of manufacture-induced porosity (uniform as well as with increasing and decreasing porosity levels with the distance from the interface) are studied. The analysis is based on a general computational scheme to determine damage evolution parameters, which incorporates a solution of the appropriate problem of thermoelasticity. It is shown that the type of the substrate interplays with the coating’s thickness in its influence upon the character and rate of damage accumulation in coatings. A number of other important features of the damage evolution process in thick ceramic coatings linked to the coating’s thickness are also revealed. © 2006 Elsevier B.V. All rights reserved. Keywords: Brittle coatings; Ceramic coatings; Damage evolution; Thermal loading 1. Introduction Protection of different structures and their components against damaging effects of various loading and environmen- tal factors is an important technological problem. To solve it, various types of protective coatings are usually used, with ceramic coatings being broadly employed in diverse engineer- ing applications, such as microelectronics, nuclear, aircraft and space engineering, in gas turbines and engines, etc. The pur- pose of ceramic coatings is to greatly improve performance, efficiency and lifetime of the metallic components and also to widen their functional applications, serving as protective heat insulating barriers, which are resistant to wear, erosion and fatigue. It is generally known that deposition technologies not only determine the structure of coatings but also cause various microstructural defects in them. For ceramic coatings, such features as manufacture-induced porosity and anisotropy in ther- momechanical properties are common. These characteristics, together with a significant mismatch in coefficients of thermal expansion of coatings and substrates, could result in damage ∗ Corresponding author. Tel.: +380 322 646818; fax: +380 322 636270. E-mail address: shevchuk@iapmm.lviv.ua (V.A. Shevchuk). evolution and crack initiation under thermal loading. It is there- fore important to study accumulation of microstructural damage as well as the influence of defects on the mechanical behaviour of ceramic coatings. To evaluate damage evolution in ceramic coatings under ther- mal loading, the approach, based on the damage evolution law [1] and application of the computational scheme, which uses finite element method to calculate temperature, strain and stress fields, has proved to be efficient [2,3]. This procedure can be simplified by incorporation of an analytical solution of the appropriate interim boundary-value problem of thermoelasticity into the modelling scheme, thus resulting in an analytico-numerical approach [4]. For the case of thin coatings [4–6], this approach is based on application of a mathematical model with generalised boundary conditions of thermomechanical conjugation of a substrate with environment via the coating. For the case of arbitrary thickness, it is possi- ble to use another approach [7] to estimate a stress–strain state in such coatings deposited on cylindrical bodies. In this paper, this algorithm is generalised and enhanced for the case of a substrate with anisotropic ceramic coating under conditions of plane strain. It is based on reduction of the interim thermoelas- ticity problem to the system of Volterra integral equations of the second kind, which are effectively solved by the iteration method [7–9]. 0921-5093/$ – see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.msea.2006.03.080