Manufacture of fluid-cooled gas turbine airfoils

Claim 1

In the method for applying a continuous skin over a turbine bucket core having a plurality of grooves recessed in the surface thereof and separated by ridges of the core material, in which method the grooves are filled with a first material, said bucket core surface is covered with at least one rigid layer of another material to form the bucket skin and said first material is then removed completing conversion of each groove to an empty enclosed passage for receiving, transporting and discharging coolant, the improvement comprising the steps of, a. selecting one material for the bucket skin, said material being capable of deposition over the bucket core as a porous layer having structural integrity, b. selecting a second material for temporarily occupying the grooves of said bucket core, said second material having a melting temperature lower than the melting temperature of said one material, said one material and the bucket core material being wet by, but not actively alloying with said second material when molten and said second material being capable of bonding said one material to itself and to said bucket core, c. disposing said second material in each of said grooves to a level approximately flush with the outer surface of said bucket core, d. depositing a porous coating of said one material over said bucket core and over the deposits of said second material and e. heating the composite so formed to a temperature above the melting point of said second material and below the melting temperature of said one material until said second material melts and is drawn from said grooves into the porous coating by capillary action to empty each of said grooves, to bond said one material together and also to bond said one material to the surfaces of said bucket core in contact therewith.