Method of forming a diffusion barrier for overlay coatings

A method of forming a diffusion barrier between a superalloy substrate and an overlay coating comprising aluminum, said method comprising, in an inert atmosphere:

• sputtering a target comprising rhenium with an energetic beam of ions in a vacuum at an energy and a current density sufficient to deposit a first film comprising a quantity of rhenium atoms on an outer surface of said superalloy substrate;
• subjecting said first film to a first temperature for a first amount of time effective to retain a majority of said quantity of rhenium atoms on said surface while causing a minor portion of said quantity of rhenium atoms to penetrate said surface;
• subsequently depositing an overlay coating onto said surface;
• and
• heating said superalloy substrate to a second temperature and for a second amount of time effective to anneal said overlay coating and to form a diffusion barrier comprising an interfacial zone coated by a second film, said interfacial zone comprising a minority of said quantity of rhenium atoms mixed with atoms of said superalloy substrate, a major portion of said rhenium atoms comprising said second film, wherein said diffusion barrier is effective to suppress diffusion of said aluminum from said overlay coating under static oxidation testing conditions.

A method of forming a diffusion barrier between a superalloy substrate and an overlay coating comprising aluminum, said method consisting essentially of, in an inert atmosphere:

• sputtering a target comprising rhenium with an energetic beam of ions in an inert atmosphere in a vacuum at an energy and a current density sufficient to deposit a first film comprising a quantity of rhenium atoms on an outer surface of said superalloy substrate;
• subjecting said first film to a first temperature for a first amount of time effective to retain a majority of said quantity of rhenium atoms on said surface while causing a minor portion of said quantity of rhenium atoms to penetrate into said surface;
• subsequently depositing an overlay coating onto said surface;
• and
• annealing said overlay coating at a second temperature for a second amount of time effective to anneal said overlay coating and to form a diffusion barrier comprising an interfacial zone coated by a second film, said interfacial zone comprising a minority of said quantity of rhenium atoms mixed with atoms of said superalloy substrate, a major portion of said rhenium atoms comprising said second film, wherein said diffusion barrier is effective to suppress diffusion of said aluminum from said overlay coating under static oxidation testing conditions.