Thermal diffusivity measurement of ceramic materials used in spraying of TBC systems

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 (ZrO 2 9 8Y 2 O 3), 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 HOSP TM type after pressing and sintering processes and calculated (2layered 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.

Thermal analysis of the ceramic material and evaluation of the bonding behavior of silicon-ceramic composite substrates

“…The thermal diffusivity is higher than 0.2 mm 2 s −1 for temperatures below 50 • C. For temperatures between 100 • C and 350 • C the diffusivity is about 0.18-0.19 mm 2 s −1 , whereas it decreases for higher temperatures to values below 0.10 mm 2 s −1 . For glass, the thermal diffusivity is given with values from 0.56 to 1.70 mm 2 s −1 and for pressed ceramic powders with values about 0.1-0.2 mm 2 s −1 in literature [17][18][19]. The measured diffusivity of LTCC is comparable to these data.…”

Review Study on Mechanical and Thermal Properties of Ceramic Materials for Future Aerospace Applications

“…Thermal diffusivity of a material can be determined by laser flash method. [36]The thermal diffusivity is greater than 0.2 mm2 s−1 for temperatures under 50 °C. For temperatures between one hundred °C and 350 °C the diffusivity is about 0.18-0.19 mm2 s−1, whereas it decreases for greater temperatures to values under 0.10 mm2 s−1.…”

Eddy Current Testing of Conductive Coatings Using a Pot-Core Sensor

“…Coatings may also provide thermal insulation, which in some applications facilitates reduction of energy loss, whereas in others it allows the utilisation of materials in working conditions involving temperatures exceeding even 1000 °C. In the latter case, the layer structure of the thermal barrier coating (TBC) type [ 6 , 7 , 8 ] can reduce the substrate surface temperature by more than 100 °C.…”