Thermal shock and fatigue resistance evaluation of functionally graded coating for gas turbine blades by laser heating method

Abstract This paper presents results of thermal shock and fatigue tests conducted on ZrO 2 -based thermal barrier coating systems under the temperature environments for advanced gas turbines. A CO 2 laser heating method was employed to heat two types of cylindrical specimens with conventional two-layer coating and functionally graded coating. Acoustic emission (AE) signals and temperatures were monitored to detect the fracture process of the coating systems. The measurements of AE signals and temperatures were correlated with the growth of coating delamination. In order to investigate the effects of heating rate and cooling rate on the coating fracture, four different heating/cooling thermal cycles were used in the thermal shock and fatigue tests. Using the AE and temperature results, the fracture process of the coating systems is examined, and the delamination growth rate during fatigue tests is determined. Based on the results, a suitable thermal cycle is determined for an accelerated testing method of the ZrO 2 -based coating systems. Finally, usefulness of application of functionally graded coating systems is discussed.