The significance of thermal contact resistance in two-layer thermal-barrier-coated turbine vanes

Thermal Conductivity of Plasma‐Sprayed Monolithic and Multilayer Coatings of Alumina and Yttria‐Stabilized Zirconia

“…The predictions for a bilayer calculated from the porosity-corrected data of fully dense materials, as well as from the experimental data for heat-treated monolithic coatings using Eq. (14), agree well with the experimental data for multilayer coatings. The overall good agreement between the measurements and both predictions suggests that heat treatment may have eliminated the effects due to the imperfect splat interfaces in the coatings and that the primary microstructural factor that influences ther- 10.…”

“…On the other hand, the estimates from Eq. (14), using the experimental conductivity data for the monolithic Al 2 O 3 and YSZ coatings, are in reasonable agreement with the multilayer data. The latter agreement may be surmised to be due to the effect of thermal resistance that results from splat interfaces and cracks, which is already contained in the experimental conductivities of the monolithic coatings.…”

“…10 reveal that the thermal conductivities that are calculated from Eq. (14), using the data for the dense materials (and accounting for porosity), are significantly higher than the experimental measurements for the multilayers. On the other hand, the estimates from Eq.…”

“…Although several previous investigations [11][12][13][14][15] generally noted the significance of these variables, there has been no controlled study to determine the specific roles and the relative influences of these variables on thermal conductivity. Specifically, the independent contributions of porosity and thermal resistance due to imperfect interfaces to the reduction in thermal conductivity are not fully understood.…”

“…From the perspective of thermal conductivity, microstructural variables that can be considered important are the coating density, interface bonding between the splats, interlayer interfaces, and the heat-transfer characteristics of the coating/ substrate interface. Although several previous investigations [11][12][13][14][15] generally noted the significance of these variables, there has been no controlled study to determine the specific roles and the relative influences of these variables on thermal conductivity. Specifically, the independent contributions of porosity and thermal resistance due to imperfect interfaces to the reduction in thermal conductivity are not fully understood.…”