Abstract: A method is provided for bonding a ceramic thermal barrier coating to a nickel or cobalt based superalloy substrate for use in high temperature applications such as gas turbine engines. The method comprises roughening the superalloy substrate itself to produce a surface roughness, preferably from 100 to 350 microinches Roughness Average (RA). The roughened surface of the substrate is treated with a diffusion coating, preferably aluminide or platinum-aluminide to provide oxidation and hot corrosion resistance, while substantially preserving the micro-topography of the roughened surface. A ceramic thermal barrier coating is applied directly to the diffusion treated surface, preferably using an air plasma spray. The surface roughness, which is left substantially undisturbed by the diffusion coating treatment, is altered by the air plasma sprayed ceramic to form a series of interlocking microstructures that firmly attach the ceramic thermal barrier coating to the diffusion treated superalloy substrate.