Materials and Design 23 (2002) 645–650 0261-3069/02/$ - see front matter  2002 Elsevier Science Ltd. All rights reserved. PII:S0261-3069 Ž 02 . 00047-X Effects of residual stress on thickness and interlayer of thermal barrier ceramic MgO–ZrO coatings on Ni and AlSi substrates using finite 2 element method Ozkan Sarikaya , Erdal Celik * a b,c, Faculty of Engineering, Department of Mechanical Engineering, Sakarya University, Esentepe Campus, Sakarya 54187, Turkey a Engineering Faculty, Department of Metallurgical and Materials Engineering, Dokuz Eylul University, Bornova, Izmir 35100, Turkey b Superconductivity Research Laboratory, ISTEC, Japan Fine Ceramic Center, 2-4-1 Mutsuno, Atsuta-ku, Nagoya 456-8587, Japan c Received 7 March 2002; accepted 2 July 2002 Abstract Thermal analysis evolution of MgO–ZrO yNiCrAlY coatings on Ni metal and AlSi alloy (LM13) substrates was studied. 2 MgO–ZrO yNiCrAlY coatings were deposited on metallic substrates using an atmospheric plasma spray technique. The coatings 2 were characterized by optical microscope and scanning electron microscope. Thermal loadings were applied to the model at the temperature range 800–1000 8C using finite element method. Methollographic examinations pointed out that coatings possessed porosity, oxide, unmelted and semi-melted particle, and inclusion. Finite element calculations showed that stress concentration was at higher levels in the coatings with AlSi substrates than that of Ni. It was also found that the larger residual stresses were obtained with an increase of the coating thickness and interlayer bond coatings decreased residual stresses.  2002 Elsevier Science Ltd. All rights reserved. Keywords: MgO–ZrO ; Finite element; Plasma spray 2 1. Introduction Plasma-sprayed thermal barrier coatings (TBCs) and functionally graded materials (FGM) are coating sys- tems that is used to increase performance of high temperature components which consist of ceramics on one side, metal on the other, and an intermediate layer which structure, composite and morphology change continuously from ceramic to metal in micro scale. It is clear that these coatings will act in the next decades an important role in industrial application fields such as automotive industries, aircrafts and aerospace applica- tions w1–4x. The hot gas turbine section of gas turbines and turbine blades has been recently coated with CaO, MgO, Y O , 23 CeO , In O , SnO , and rare earth oxides stabilized 2 23 2 ZrO for thermal isolation, due to the fact that marten- 2 sitic transformation has found ZrO -based materials and 2 then a stress induced phase transformation can be used *Corresponding author. Fax: q90-232-388-78-64. E-mail address: erdal.celik@deu.edu.tr (E. Celik). to increased the fracture thoughness of brittle materials based on ZrO . Transformation to its stable, monoclinic 2 structure in the vicinity of the crack front is believed to be responsible for the increased fracture thoughness, and this phase transformation has been established to be martensitic in nature. NiCrAlY are used as a bond coat in order to increase adhesion between the ceramic coating and the substrate w5–17x. Thermal spraying techniques such as plasma spraying have been used to produce ceramic coatings to improve the thermal barrier properties of the materials. These advanced ceramics show super performance at high temperatures. Conven- tional TBCs have low durability during thermal cycles. The reasons of examining of FGM are reducing thermal stresses, increasing thermal-mechanic fatigue life and adhesion strength w18–21x. Finite element method (FEM) has been used to study the stresses in a number of problems where material properties differ across an interface of the coatings w21x. In this research, the effects of coating thickness and interlayer against thermal loadings of MgO–ZrO y 2