Comparison of the developed thermal stresses in Al2O3–SG, ZrO2–12%Si+Al and ZrO2–SG coating systems subjected to thermal loading

The effect on residual stresses of porosity in plasma sprayed MgO–ZrO2 coatings for an internal combustion diesel engine

“…The MgO-ZrO 2 ceramic coatings exhibit lower thermal diffusivity values than those of plasma sprayed metal coatings due to the fact that ceramic materials have a relatively high percentage of porosity [13]. The mechanical and thermal properties of the substrate and the coating are listed in Table 1 [4,13,16,17]. Prior to coating process, Al-Si piston alloys with dimension of 50 mm × 40 mm × 4 mm were pretreated by applying grit-blasting using 35-mesh Al 2 O 3 , followed by ultrasonic cleaning and degreasing in a Freon solvent, which is methanol.…”

“…Thermal barrier ceramic coatings (TBCs) are typically applied to exhaust valves for an internal combustion diesel engine via a plasma spray system at high temperatures [1][2][3][4][5][6]. On cooling, thermal residual stresses develop due to differences in the properties of the materials, particularly thermal expansion coefficients.…”

“…Such stresses exist even if the cooling process is sufficiently slow for the temperature to remain spatially uniform, and can be large enough to cause the component to fail. A numerical solution of the basic equations of mechanics can provide estimations of residual thermal stress and strain levels both in the valve body and the TBCs [1,4,7].…”

“…With respect to temperature changes in the TBC (either during their processing or their application), probably the most important thermal property is thermal expansion coefficient. For a given temperature change, thermal stresses are directly related to thermal expansion difference between two constitute materials [1,4,10].…”

Residual stress redistribution within high-temperature coatings due to surface cracks

“…It is well known that the performance of a TBC is dependent on application and upon the overall properties of the coating and substrate combination. During the deposited process of a TBC, difficulties arise due to the mismatches in elastic moduli, coefficients of thermal expansion (CTEs) between the coating and the substrate, and the elastic-plastic deformation of bondcoat and substrate [2,3]. Because of these differences, residual stresses are generated inevitably.…”