Method of fabricating composite nozzles for water cooled gas turbines

An improved method of making a water-cooled turbine nozzle comprising the steps of:

• (a) forming a copper or copper alloy airfoil core having longitudinal holes extending through said core at predetermined locations, and placing a first plurality of cooling tubes in said holes;
• (b) forming a top endwall having a composite structure comprising a first upper layer of stainless steel and a first lower layer of high thermal conductivity copper consolidated from metal powder, said endwall having a second plurality of cooling tubes embedded in said first lower layer and extending through said first upper layer;
• (c) forming a bottom endwall having a composite structure comprising a second lower layer of stainless steel and a second upper layer of high thermal conductivity copper consolidated from metal powder, said endwall having a third plurality of cooling tubes embedded in said second upper layer and extending through said second lower layer;
• (d) preforming a corrosion resistant outer cladding in the shape of a hollow body open at both ends and having substantially the external dimensions of said nozzle;
• (e) placing the bottom endwall, the airfoil and the top endwall in said hollow cladding body and joining both endwalls and the airfoil together with a plurality of spar rods;
• (f) welding said spar rods, said cooling tubes and said cladding body to said endwalls to form an assembly;
• (g) evacuating air from said assembly and sealing under vacuum;
• (h) diffusion bonding said assembly under hot isostatic pressure;
• and
• (i) machining said bonded assembly to the finished product.