An air cooled airfoil for use in a gas turbine engine includes a base, a
porous material on the base, and a thermal barrier coating (TBC) applied
to the porous material, with cooling holes in the base and the TBC to
allow for cooling air to flow from within the airfoil to the surface of
the airfoil, and where the porous material has a higher density near the
TBC interface than at the base interface. The higher density at the TBC
interface provides for a rigid support structure for the TBC as well as
higher heat transfer than would the lower density porous material near
the base, the lower density porous material near the base acting to
reduce heat transfer to the base and therefore promote heat transfer into
the cooling air passing through the porous material and out onto the
airfoil surface. An additional embodiment includes an airfoil having a
plurality of outward facing cavities, each cavity being filled with a
porous material having varying density and covered with a TBC layer.