Oxide film removing method

Abstract

An oxide film removing method is a method of removing an oxide film formed in a surface of a superalloy part that contains a first metal as a base metal and a second metal different from the first metal. The oxide film removing method includes arranging the superalloy part inside a heating chamber; reducing the oxide of the base metal to the base metal by heating the inside of the heating chamber in a condition that a reduction gas atmosphere or a vacuum atmosphere is maintained; and carrying out acid processing to apply acid solution to the superalloy part after the reduction. The oxide film formed in the surface of the superalloy is removed effectively without using a highly toxic gaseous fluoride.

1 . An oxide film removing method of removing an oxide film formed in a surface of a superalloy part that contains a first metal as a base metal and a second metal different from the first metal, the oxide film containing oxide of the base metal and oxide of the second metal,
 the oxide film removing method comprising:   arranging the superalloy part inside a heating chamber;   preparing a reduction gas atmosphere or a vacuum atmosphere inside the heating chamber;   reducing the oxide of the base metal of the oxide film to the base metal by heating the inside of the heating chamber in a condition that the reduction gas atmosphere or the vacuum atmosphere is maintained; and   carrying out acid processing to apply acid solution to the superalloy part after the reduction,   wherein the acid processing comprises:   dissolving the base metal; and   separating the oxide of the second metal left without being reduced through the reduction, from the superalloy part together with the dissolved base metal.   
     
     
         2 . The oxide film removing method according to  claim 1 , wherein the acid processing is carried out after the reduction. 
     
     
         3 . The oxide film removing method according to  claim 1 , wherein the base metal is nickel or cobalt. 
     
     
         4 . The oxide film removing method according to  claim 1 , wherein the oxide of the second metal is a metal oxide in which thermodynamic stability is higher than that of the oxide of the base metal. 
     
     
         5 . The oxide film removing method according to  claim 1 , wherein the second metal contains at least one of aluminum, titanium, and chrome. 
     
     
         6 . The oxide film removing method according to  claim 5 , wherein the second metal contains aluminum. 
     
     
         7 . The oxide film removing method according to  claim 1 , wherein the acid solution contains hydrochloric acid. 
     
     
         8 . The oxide film removing method according to  claim 1 , wherein the superalloy part has a crack, and
 wherein the oxide film contains an oxide film formed in a surface of the crack.   
     
     
         9 . The oxide film removing method according to  claim 8 , wherein the method does not contain expanding a crack physically. 
     
     
         10 . The oxide film removing method according to  claim 1 , wherein the method does not contain a fluoride ion cleaning process.