Thermal Cycling Life of Porous Ceramic Coatings Subjected to Thermal Gradient and Coolant Pressure

A transpiration cooling system for gas turbine applications has significant benefit to reduce the amount of cooling air and to increase cooling efficiency. We had developed a porous ceramic coating deposited by plasma spraying process, which can infiltrate cooling gas, and examined about those mechanical properties. In this study, thermal cycling life of this porous ceramic coating is revealed in order to apply this technology to advanced gas turbine blade in practical use. The thermal cycling test is conducted by using the hand-made device which can heat cyclically up and down around the surface of the porous coating while infiltrating cooling gas. The number of thermal cycles up to reach the coating delamination is related with maximum exposed temperature and pressure of the cooling gas as the test condition, consequently.

The Effect of Pore Shape to the Effective Thermal Conductivity of Thermal Barrier Coatings

Effective thermal conductivity is an important parameter for the design of porous ceramic coatings that are exposed to high temperatures. Pore shapes which change in relation with the coating parameters and coating method affect the effective thermal conductivity significantly. In this study the effective thermal conductivity of 8 wt % yttria stabilized ZrO2 coating deposited by air plasma spraying have been calculated by finite element method using digital images. The effects of pore shape on effective thermal conductivity have been discussed.