Hiromitsu Takeda

Relationship between microstructure of plasma-sprayed 8YZ coatings and thermal fatigue life of thermal barrier coatings

Microstructure of plasma-sprayed yttria-stabilized zirconia coatings (8YZ) was characterized by the measurement of surface roughness, hardness, and pore size distribution and was correlated with thermal fatigue life. It was confirmed that the coatings which had greater roughness tended to show both lower hardness and higher porosity. Furthermore, such coatings were found to have a longer thermal fatigue life. We propose that measurement of the roughness of 8YZ coatings is useful as a non-destructive evaluation method for predicting thermal fatigue life.

Properties of plasma sprayed CeO2ZrO2Y2O3 thermal barrier coating

The plasma sprayed CeO2-ZrO2-Y2O3 thermal barrier coating was developed, and thermal conductivity, thermal expansion, bending strength and hot corrosion resistance were evaluated. The results indicated that CeO2-ZrO2-Y2O3 compositions are useful for the plasma sprayed thermal barrier coatings. The thermal conductivity of the sprayed CeO2-ZrO2-Y2O3 coating was 1-2W/m・K, lower than that of sintered materials of the same composition and one of the lowest thermal conductivities of ceramics. Thus, the CeO2-ZrO2-Y2C3 coating is useful for the thermal barrier, since the sprayed layer is expected to insulate heat flow well. The thermal expansion coefficient of the sprayed CeO2-ZrO2-Y2O3 coating was 12×