Cerium-containing austenitic nickel-base alloy having enhanced intergranular attack and stress corrosion cracking resistances, and preparation method thereof

Abstract

The present invention relates to a cerium-containing austenitic nickel-base alloy having enhanced IGA(intergranular attack) and SCC(stress corrosion cracking) resistances, and a preparation method thereof. The cerium-containing alloy according to the present invention is prepared by adding cerium to an austenitic nickel-base alloy, which is used as a material of heat tubes of a steam generator in a nuclear power plant. The cerium-containing alloy has a refiner grain size than the conventional alloy without cerium, a semi-continuous distribution of intergranular carbides, and improved intergranular attack and stress corrosion cracking resistances in the environment of high temperature and base.

1 . A cerium-containing austenitic nickel-base alloy having the cerium content of 0.02˜0.09 wt %.  
   
   
       2 . The cerium-containing austenitic nickel-base alloy of  claim 1 , wherein the cerium content is 0.04 wt %.  
   
   
       3 . The cerium-containing austenitic nickel-base alloy of  claim 1 , wherein the alloy contains 58˜80 wt % of nickel, 14˜31 wt % of chromium, 6˜11 wt % of iron, and 0.01˜0.15 wt % of carbon, as major components.  
   
   
       4 . The cerium-containing austenitic nickel-base alloy of  claim 1 , wherein the grain size of the alloy is 25˜60 μm.  
   
   
       5 . The cerium-containing austenitic nickel-base alloy of  claim 4 , wherein the grain size of the alloy is 35 μm.  
   
   
       6 . The cerium-containing austenitic nickel-base alloy of  claim 1 , wherein the alloy has the mechanical properties of: 200˜350 MPa of yield strength, 550˜750 MPa of ultimate tensile strength, and above 30% of elongation.  
   
   
       7 . A preparation method of a cerium-containing austenitic nickel-base alloy comprising the steps of: 
 preparation of an ingot by adding 0.02˜0.09 wt % of cerium to an austenitic nickel-base alloy composition;    homogenizing heat treatment of the ingot after surface grinding;    preparation of a hot rolled material by hot rolling the heat-treated ingot;    removal of surface oxide film by acid pickling the hot rolled material;    preparation of a cold rolled material by cold rolling the material after hot rolling and removal of oxide film;    solution annealing of the cold rolled material; and    thermal treatment of the solution annealing material.    
   
   
       8 . The preparation method of a cerium-containing austenitic nickel-base alloy of  claim 7 , wherein the solution annealing is performed at 900˜1200° C. for 5˜60 min.  
   
   
       9 . The preparation method of a cerium-containing austenitic nickel-base alloy of  claim 8 , wherein the solution treatment is performed at 1010° C. for 10 min.  
   
   
       10 . The preparation method of a cerium-containing austenitic nickel-base alloy of  claim 7 , wherein the thermal treatment is performed at 700˜720° C. for 10˜20 hours.  
   
   
       11 . The preparation method of a cerium-containing austenitic nickel-base alloy of  claim 10 , wherein the thermal treatment is performed at 704° C. for 15 hours.