disposing a bond coating on the airfoil, where the airfoil comprises a concave pressure wall, a convex suction wall and cooling channels; where the concave pressure wall extends radially from a base to a tip of the airfoil and where the convex suction wall contacts the concave pressure wall at a leading edge and at a trailing edge spaced axially from leading edge; where the airfoil comprises a material that has an initial composition;

machining a cooling hole in the airfoil to contact the cooling channels such that a fluid travelling in the cooling channel may be discharged via the cooling hole; where the machining of the cooling hole results in a formation of a depleted region around the cooling hole; where the depleted region is depleted of a portion of the initial composition of the airfoil;

disposing a top coat on the bond coat; and

subjecting the airfoil to a heat treatment at a temperature effective to promote diffusion of elements from a non-depleted region to the depleted region around the cooling hole; where the non-depleted region is located further away from the cooling hole than the depleted region.