Thermal Cycling Tests of Thermal Barrier Coatings—Comparison of Laser Rig Test and Simulated Flame Torch Rig Test
Yao Wang, Lei Zhao, Xiwen Liu, Pei‐feng HsuABSTRACT
The thermal cycling test is an effective method for evaluating the performance of thermal barrier coatings (TBCs). Although a testing standard, ISO 13123, exists, most of the temperature gradient test rigs do not comply with the requirements specified in this standard. As such, it is difficult to compare test results from one test rig versus those from another test rig. In this study, the temperature gradient cycling tests were conducted using a high‐power CO 2 laser rig under two heating control modes, constant temperature and constant laser power and airflow. Two types of temperature distributions, uniform and Gaussian profiles, were applied to compare the effect on coating failure. The uniform profile meets the requirements of the ISO standard, and the Gaussian profile simulates a flame‐torch test. Results show that the heating control and the applied temperature distribution on the topcoat significantly impact the coating failure in the cycling test. The finite‐element analyses were conducted to determine transient stress and strain distributions to explain the coating failures. Simulation results show that the Gaussian temperature on the top surface has a stronger stress concentration than that of the uniform temperature distribution, which explains the faster failure observed for the Gaussian heating condition in the experiments.