Thermal fracture of thermal barrier coatings in a high heat flux environment

The objective of this research was to study the response of thick thermal barrier coatings to high heat flux environments. High heat flux environments subject the coating to large transient thermal loads. In this paper, the thermal fracture process of coatings manufactured in different ways under controlled thermal loading conditions is presented. The transient thermal loads were applied, using a 1.5 kW CO2 laser, to steel beam specimens plasma sprayed with yttria partially stabilized zirconia. Laser heating was found to sinter the heated regions of the coating. A 0.76 mm thick coating resulted in multiple surface cracks, whereas a thicker 1.09 mm coating resulted in surface and interface cracks. The effect of a common procedure of interrupting plasma spraying, reheating, and continuing plasma spraying was investigated. If the stress field due to a thermal heating event was of sufficiently high intensity, and it coincided with a plane of weakness within the coating, it was possible to cause delamination at that plane. (orig.)