Method for separating a metal part from a ceramic part

Abstract

The invention relates to a method for separating a metal part from a ceramic part, which are joined at a connecting face within a modular hybrid component, especially of a gas turbine. The method includes said component being subjected to a reducing atmosphere in a gaseous process at elevated temperatures to dissolve the connection between said metal part and said ceramic part, especially by dissolving the ceramic part itself.

1 . A method for separating a metal part from a ceramic part, which are joined at a connecting face within a modular hybrid component, especially of a gas turbine; the method comprising; said modular hybrid component is subjected to an inert/reducing atmosphere in a gaseous process at elevated temperatures to dissolve the connection between said metal part and said ceramic part. 
     
     
         2 . The method according to  claim 1 , wherein said reducing atmosphere contains halogens as reactive species. 
     
     
         3 . The method according to  claim 2 , wherein said halogens have a higher electronegativity than oxygen, on either Pauling Scale, Mulliken Scale or Allred-Rochow Scale. 
     
     
         4 . The method according to  claim 3 , wherein said halogens comprise F. 
     
     
         5 . The method according to  claim 3 , wherein said halogens comprise Cl. 
     
     
         6 . The method according to  claim 1 , wherein said ceramic part itself is dissolved or disintegrated as a whole. 
     
     
         7 . The method according to  claim 6 , wherein said ceramic part is a partially or fully stabilized ceramic, whereby, during the process, the stabilizing phase is removed by phase change from the ceramic, such that the entire ceramic destabilizes and is readily removed or spalls of, as soon as the content of the stabilizing phase decreases below a stability limit. 
     
     
         8 . The method according to  claim 7 , wherein said ceramic part is a partially or fully stabilized oxide ceramic. 
     
     
         9 . The method according to  claim 8 , wherein said partially or fully stabilized oxide ceramic is zirconia stabilized with a rare earth or an alkaline earth element or combinations thereof. 
     
     
         10 . The method according to  claim 9 , wherein said rare earth or alkaline earth element is one of Sc, Y, Sm, Mg, Ca, Ce, Ta or Sr. 
     
     
         11 . The method according to  claim 6 , wherein said ceramic part contains an alkali silicate, alkali borosilicate, earth alkali silicate, earth alkali borosilicate or any of those compounds with the addition of a semimetal or metalloid, and that, during the process, the halogen attacks the Si containing phase, which results in dissolution and removal of the entire ceramic. 
     
     
         12 . The method according to  claim 1 , wherein a joint layer is disposed between said metal part and said ceramic part, and that said halogen attacks said joint layer, such that said metal part and said ceramic part are separated from each other. 
     
     
         13 . The method according to  claim 12 , wherein said joint layer comprises a braze alloy and/or a mineral glue or cement. 
     
     
         14 . The method according to  claim 1 , wherein said hybrid component is put in a reactor, which is heated to more than 850° C., preferably to more than 1000° C. but not more than 1150° C. 
     
     
         15 . The method according to  claim 1 , wherein said process is conducted as a batch process to allow economic ceramic-metal separation for entire sets in very short time. 
     
     
         16 . The method according to  claim 1 , wherein the metal part and/or ceramic composite part is simultaneously cleaned in said process, such that it can be brazed without further cleaning or oxide removal and, in case no rework of the metal part is required, is immediately ready for joining with a new ceramic part, and/or the ceramic composite part can be re-used.