Investigation of thermal shock properties of thermal barrier coatings

Thermal barrier coatings are high temperature insulators that are applied onto metallic substrates to prevent the substrate from high temperature oxidations. TBC system occurs from two different layers as one metallic based and the other is ceramic. A TBC consists of a heat-resistant ceramic top coat and a metallic bond coat. The bond coat?s main purpose is to attach the top coat to the substrate, but the bond coat also prevents or delays oxidation of the substrate. Unfortunately, a major life-limiting weakness of TBC?s is oxidation of the bond coat itself; the other major problem is their susceptibility to damage by thermally-induced stresses.Ceramics are fragile materials and typically their thermal conductivity coefficient generally is low. These characteristics make them sensitive against thermal stress which causes from temporary or constant heat transfer. When ceramic materials are submitted sudden thermal changes (thermal shock) significant stresses come into being on the material. Consequently, one of the most important elements that determines the life of the coating is the thermal shock resistance.The aim of this thesis is to investigate the thermal shock effect which is directly determine the life of the thermal coatings often used in high temperature applications and to define the harm mechanism which occurs as a result of this effect. In this way YSZ (ZrO2 - wt. 8% Y2O3) and CSZ (ZrO2 ? wt.% 2.5 Y2O3 ? wt.%25 CeO2) powders are plazma sprayed and tested in a thermal shock test mechanizm which is designed specially.