Steam turbine bucket with erosion durability

Abstract

A method for forming a bucket for a steam turbine includes forming a leading edge on at least one airfoil. The leading edge is comprised of an erosion resistant material and is bonded to the airfoil.

1 . A method for forming a bucket for a steam turbine comprising forming a leading edge on at least one airfoil by bonding an erosion-resistant material to the airfoil. 
     
     
         2 . The method of  claim 1  wherein the erosion-resistant material is fusion bonded to the airfoil. 
     
     
         3 . The method of  claim 1  wherein the erosion-resistant material is fusion bonded to the airfoil by a laser cladding process. 
     
     
         4 . The method of  claim 1  wherein forming the leading edge comprises forming a plurality of layers of erosion-resistant material. 
     
     
         5 . The method of  claim 1  wherein the erosion-resistant material comprises a stellite alloy. 
     
     
         6 . The method of  claim 5  wherein the erosion-resistant material further comprises one or more refractory metals. 
     
     
         7 . The method of  claim 6  wherein the one or more refractory metals includes chromium, molybdenum, tungsten, nickel, tantalum, and/or vanadium. 
     
     
         8 . The method of  claim 1  wherein the leading edge is formed by laser gas nitriding. 
     
     
         9 . The method of  claim 1  wherein the leading edge is substantially cobalt-free. 
     
     
         10 . The method of  claim 1  wherein a bucket substrate is a titanium-based alloy. 
     
     
         11 . The method of  claim 10  wherein the erosion-resistant material is base-matched to the titanium-based alloy. 
     
     
         12 . The method of  claim 1 , wherein the bucket comprises a last stage bucket. 
     
     
         13 . The method of  claim 1 , wherein the steam turbine comprises a plurality of airfoils.