Effect of interface roughness and coating thickness on interfacial shear mechanical properties of EB-PVD yttria-partially stabilized zirconia thermal barrier coating systems

The effect of interface roughness and thickness of thermal barrier coating (TBC) on the interfacial shear mechanical properties of electron beam-physical vapor deposited (EB-PVD)-TBC was examined using as-sprayed and polished bond coats (BC) 200 μm and 500 μm TBC thickness systems, by using a barb test method. The residual compressive stress in the TBC layer from the interface to the top surface was measured, by using Raman spectroscopy. The interface toughness related to the interface roughness and the thickness of the TBC. The interface toughness was larger for the BC as-sprayed TBC system than for the BC polished TBC system. The delamination of the TBC propagated within the TBC layer adjacent to the interface for the BC as-sprayed TBC; for the BC polished TBC, this occurred at the interface between the TGO and the BC. Moreover, the interface toughness was larger in the 500 μm thickness TBC than in the 200 μm thickness TBC. The relation of interface toughness to interface roughness and thickness of the TBC was associated with the interface residual compressive stress and with the interface sliding friction during the delamination of TBC.