Experimental study on thermal cycle performance of DD6 single crystal thermal barrier coating with film cooling holes

Abstract

Film-cooling holes play a critical role in increasing the inlet temperature of aviation gas turbine engines. However, the presence of these cooling holes can lead to local thermal and mechanical stresses during cold-hot cycling and high-temperature gas erosion, resulting in coating spallation along the cooling holes. Moreover, the use of picosecond laser drilling can exacerbate the coating's failure at these damaged locations. This study conducts thermal cycling experiments on DD6 single-crystal thermal barrier coatings with cooling holes, analyzing the effects of hole structure and laser processing on the thermal cycling life, surface morphology, and microstructure of the thermal barrier coatings. The results indicate that the damage and failure of the coatings are less severe for non-conventional holes compared to inclined holes, and the thermal cycling life of non-conventional holes is higher than that of inclined holes. The sharp side of the non-conventional hole exhibits smaller damage area compared to the inclined hole, while the blunt side shows no significant damage. Furthermore, when using a scanning speed of 300 mm/s and a spacing of 0.025 mm, the non-conventional holes demonstrate minimal coating damage and superior thermal cycling performance. Finally, the failure mechanism of thermal barrier coatings is analysed.