Porosity and thermal cycling behavior of plasma sprayed and EBPVD thermal barrier coatings

Traditionally, thermal barrier coatings (TBCs) are used in gas turbine engines to create an insulation layer between the metallic components and the gases in the hot section. Atmospheric plasma spray (APS) is a common method used to produce TBCs. The goal of this study is to study the porosity and thermal cycling behavior of standard (STD) and vertically cracked (VC) thermal barrier coatings (TBCs) fabricated by Atmospheric Plasma Spray (APS) for two different thicknesses, 300 and 600 lam respectively. Electron Beam Physical Vapor Deposition (EBPVD) coatings with 300 micron thickness prepared under tumbled and non-tumbled conditions were studied. For this study, mercury porosimeter equipment (POREMASTER 33) by Quantachrome Instruments was used to measure porosity, and pore size distribution. Scanning Electron Microscopy (SEM) images were obtained for all the samples. The images showed clear microstructural difference between the APS and EBPVD coatings. All the coatings were thermal cycled to 1200 degrees C and the conventional APS-STD (300m) performed the best followed by APS-VC coatings and EBPVD coatings which performed similarly.