Abstract
The basic goal of this article was thermal diffusivity characterization of ceramic materials used in thermal barrier coating (TBC) systems for depositions of the insulation layer and characterization of the materials’ morphology and remanufacturing process. The base material was oxide 8YSZ (ZrO2 × 8Y2O3), which is usually dedicated to deposition of an insulating top layer in TBC systems. The data related to thermal properties such as thermal diffusivity and thermal conductivity are widely presented in the literature, but there is lack of information about the morphological form of investigated materials, and the presented results vary widely. Data on thermal properties based on the literature sources are inadequate for the real morphological form of materials used in the experiment (e.g., massive or single crystalline material vs. plasma-sprayed coatings), which consequently gives an unsatisfactory accuracy of the obtained numerical simulations by MES methods. This article presents the characterization of thermal diffusivity of the commercial 8YSZ ceramic material synthesized or remanufactured by different routes, which is investigated in the forms of pressed powder pellet (two commercial nano-sized powders with different morphologies), sintered pellets (one commercial powder, solid-state co-precipitated reacted powder of 8YSZ type), and a two-layered coating system of In625 + NiCrAlY/8YSZ type. The range of analysis included morphological investigations of different types of powders in initial conditions and after remanufacturing (sintering, thermal spraying) as well as the thermal diffusivity analysis by the laser flash method. The obtained data were corrected by porosity factor and compared to each other. The best similarity for obtained thermal diffusivity data was found for commercial powers of HOSPTM type after pressing and sintering processes and calculated (2-layered model) value of thermal diffusivity for two-layered system of In625/8YSZ TBS system. The results showed that there are significant differences in thermal diffusivity values for materials with different morphological forms.
Highlights
The basic role of ceramic top-coats in thermal barrier coatings systems is thermal insulation of the metallic substrate during operations at high temperature with additional assistance of a strong aggressive environment
The results showed that there are significant differences in thermal diffusivity values for materials with different morphological forms
The main goal of this article is the overall characterization of the ZrO2 9 8 mass% Y2O3 ceramic material, which is typically used as a feedstock powder for deposition of the insulation layer in thermal barrier coating (TBC) systems and characterization of thermal diffusivity of these materials according to their morphological forms created with different routes of synthesis or remanufacturing
Summary
The basic role of ceramic top-coats in thermal barrier coatings systems is thermal insulation of the metallic substrate during operations at high temperature with additional assistance of a strong aggressive environment. The function of the top-coat is to decrease the temperature to at least 300 °C, under the assumption that the thickness of the ceramic insulation is generally no higher than 300 lm. This assumption requires the knowledge of the thermal properties of the ceramic materials used in TBC deposition, especially the thermal conductivity or diffusivity in a wide temperature range [3,4,5]. Thermal conductivity and diffusivity are important in the numerical modeling of the temperature and the stress distribution in the ceramic layer
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