High-temperature member for use in gas turbine

Abstract

A high-temperature member for use in a gas turbine is formed from a cobalt-based alloy comprising 15-35 wt % of chromium; 0.02-1.5 wt % of silicon; 0.01-0.2 wt % of carbon; at least one kind of metal selected from the group consisting of niobium, tungsten, tantalum and rhenium, the total content of these four metals being controlled not to exceed 10% by atomic ratio of the entirety of the alloy excluding carbon; and at least one metal selected from the group consisting of nickel, manganese and iron, the total content of these metals being within a range of 1-9 wt %, the total content of nickel being controlled not to exceed 5 wt %, and the cobalt-based alloy having both of excellent resistance due to work hardening of the matrix and excellent ductility under room temperature. Then, in order to improve the high-temperature wear resistance, a pre-hardened layer is formed in the surface portion of the member by shot peening

1 . A high-temperature member for use in a gas turbine, said member being formed from a cobalt-based alloy which comprises 15-35 wt % of chromium; 0.2 to 2.86 wt % of nickel; 0.02-1.5 wt % of silicon; 0.01-0.2 wt % of carbon; at least one kind of metal selected from four refractory metals including 0.3-8 wt % of niobium, 1-20 wt % of tungsten, 1-10 wt % of tantalum and 0.3-10 wt % of rhenium, the total content of said four refractory metals being controlled not to exceed 10% by atomic ratio of the entirety of said alloy excluding carbon; and the balance being cobalt, said member having a hardened layer formed by shot peening at least in a surface portion in contact with another member. 
   
   
       2 . The high-temperature member for use in a gas turbine, said member being formed from a cobalt-based alloy according to  claim 1 , wherein said alloy further comprises 0.5-12 wt % of molybdenum, and the total content of the five kinds of molybdenum, niobium, tungsten, tantalum and rhenium is controlled so as not to exceed 10% by atomic ratio of the entirety of said alloy excluding carbon. 
   
   
       3 . The high-temperature member for use in a gas turbine, said member being formed from a cobalt-based alloy according to  claim 1 , wherein said alloy further comprises 0.1-4 wt % of germanium. 
   
   
       4 . The high-temperature member for use in a gas turbine, said member being formed from a cobalt-based alloy according to  claim 2 , wherein said alloy further comprises 0.1-4 wt % of germanium. 
   
   
       5 . A high-temperature member for use in a gas turbine, said member comprising:
 a cobalt-based alloy including
 15-35 wt % of chromium, 
 0.02-1.5 wt % of silicon, 
 0.01-0.2 wt % of carbon, 
 at least one refractory metal from the group consisting of 0.3-8 wt % of niobium, 1-20 wt % of tungsten, 1-10 wt % of tantalum and 0.3-10 wt % of rhenium, the total content of said four refractory metals being not greater than 10% by atomic ratio of said alloy excluding carbon, 
 at least one metal from the group consisting of nickel in the amount of, 0.2 to 2.86 wt % of nickel, at most 0.63 wt % of manganese and iron, the total content of nickel, manganese and iron between 1-9 wt %, and 
 the balance of the alloy is cobalt, 
   wherein
 said member has a hardened layer formed by shot peening at least in a portion of a surface of the member which is in contact with another member when the member is assembled in the gas turbine. 
   
   
   
       6 . The high-temperature member according to  claim 5 , wherein
 said alloy further includes 0.5-12 wt % of molybdenum, and   the total content of molybdenum and said refractory metals is not greater than 10% by atomic ratio of said alloy excluding carbon.   
   
   
       7 . The high-temperature member according to  claim 5 ,
 wherein said alloy further includes 0.1-4 wt % of germanium.   
   
   
       8 . The high-temperature member according to  claim 6 ,
 wherein said alloy further includes 0.1-4 wt % of germanium.   
   
   
       9 . A method of forming a high-temperature member for use in a gas turbine, comprising the steps of:
 providing a cobalt-based alloy including
 15-35 wt % of chromium, 
 0.02-1.5 wt % of silicon, 
 0.01-0.2 wt % of carbon, 
 at least one refractory metal from the group consisting of 0.3-8 wt % of niobium, 1-20 wt % of tungsten, 1-10 wt % of tantalum and 0.3-10 wt % of rhenium, 
 at least one metal from the group consisting of nickel, manganese and iron, and 
 the balance of the alloy is cobalt; and 
 shot peening at least a portion of a surface of the member, 
   wherein
 the total content of said refractory metals is not greater than 10% by atomic ratio of said alloy excluding carbon, and 
 the total content of said metal selected from the group consisting of nickel, manganese and iron metals is within a range of 1-9 wt %, with the total content of nickel not greater than 5 wt %. 
   
   
   
       10 . The method according to  claim 9 , wherein
 said alloy further includes 0.5-12 wt % of molybdenum, and   the total content of molybdenum and said refractory metals is not greater than 10% by atomic ratio of said alloy excluding carbon.   
   
   
       11 . The method according to  claim 9 ,
 wherein said alloy further includes 0.1-4 wt % of germanium.   
   
   
       12 . The method according to  claim 10 ,
 wherein said alloy further includes 0.1-4 wt % of germanium.   
   
   
       13 . The high-temperature member according to  claim 1 , further comprising:
 at least one metal selected from the group consisting of 0.2 to 0.63 wt % of manganese and iron, the total content of said nickel, manganese and iron being within a range of 1-9 wt %.