System for applying a continuous surface layer on porous substructures of turbine airfoils

A method of forming a surface coating to an outer surface of a metallic foam of a turbine engine cooling system, comprising:

• infiltrating a porous structure with a ceramic filler forming a portion of the turbine engine cooling system with a removable filler;
• removing filler from the outer surface of the foam to expose a porous structure of the foam, whereby portions of the porous structure extend outwardly from a newly formed outer surface of the filler;
• applying a surface layer to the outer surface of the filler and exposed portions of the porous structure, whereby the surface layer is attached to the porous structure at least in part due to mechanical interaction with the portions of the porous structure extending outwardly from the newly formed outer surface of the filler;
• and
• removing the filler material from the porous structure.