Investigation of cooling hole blockage in the plasma spraying of thermal barrier coatings on super-alloy

Ceramic materials will get deposited inside pre-drilled cooling holes and partially or completely block during thermal barrier coating (TBC). In this study, the hole blockage produced by atmosphere plasma spraying (APS) was investigated using industrial computed tomography. The results show that the geometric features of the blockage owing to APS coating are significantly affected by the inclination angle of the pre-drilled holes. The coating deposition in the vertical holes is rotationally symmetric and mainly concentrates at the entrance. For the inclined holes, the deposition on the trailing edge is much more than that on the leading edge. The deposition height and length on the trailing edge increase with the inclination angle; however, they are little disturbed by the hole size. Therefore, the blockage ratio decreases with the increase of the hole size. In addition, greater TBC thickness causes larger deposition height and length and subsequently results in a larger blockage ratio.