Method of Forming a Diffusion Barrier for Overlay Coatings

Superalloy substrates bearing a rhenium diffusion barrier, and a method of forming a rhenium diffusion barrier between a
superalloy substrate and an overlay coating comprising aluminum. The method involves depositing a rhenium film onto the
surface of a superalloy substrate and subjecting the rhenium film to first conditions effective to cause a minor portion of rhenium
atoms to penetrate the surface of the superalloy substrate and second conditions effective to cause a minority of the rhenium
atoms to diffuse into the substrate, forming a diffusion barrier comprising an interfacial zone comprising a mixture of rhenium
atoms and atoms of the superalloy substrate covered by a rhenium film. The diffusion barrier is effective to suppress diffusion of
aluminum from the overlay coating under static oxidation testing conditions.