Method for modifying surface of titanium or titanium alloy by fluidized bed carburization

Abstract

The present invention relates to a method for modifying the surface of titanium or a titanium alloy by a fluidized bed carburization process. The surface hardness of the titanium or the titanium alloy could be improved by the fluidized bed carburization process. The above-mentioned method includes the following steps: providing a fluidized bed furnace, in which a carburizing agent containing charcoal and carbonate powders of which the weight ratio is 10˜8:0.5˜2 is used; placing titanium or a titanium alloy in the fluidized bed furnace at the temperature ranging from 900° C. to 1200° C. for carburizing the titanium metal or the titanium alloy for a period more than 3 minutes; and then taking the titanium metal or the titanium alloy out for quenching.

1 . A method for modifying the surface of titanium or a titanium alloy by a fluidized bed carburization process, comprising:
 providing a fluidized bed furnace, in which a carburizing agent containing a charcoal and carbonate salt powder of which the weight ratio is 10˜8:0.5˜2 is used;   placing the titanium or the titanium alloy in the fluidized bed furnace at the temperature ranging from 900° C. to 1200° C. for carburizing the titanium or the titanium alloy for a period more than 3 minutes; and   taking the titanium or the titanium alloy out for quenching.   
   
   
       2 . The method as claimed in  claim 1 , wherein alumina powder is used in the fluidized bed furnace and mixed with the charcoal and the carbonate powder. 
   
   
       3 . The method as claimed in  claim 1 , wherein the carbonate salt powder is selected from the group consisting of magnesium carbonate powder, calcium carbonate powder, strontium carbonate powder, barium carbonate powder and a mixture thereof. 
   
   
       4 . The method as claimed in  claim 1 , wherein the carbonate salt powder is barium carbonate powder. 
   
   
       5 . The method as claimed in  claim 1 , wherein the charcoal is Acacia Koa charcoal. 
   
   
       6 . The method as claimed in  claim 1 , wherein the size of the charcoal ranges from 6 to 12 mesh. 
   
   
       7 . The method as claimed in  claim 1 , wherein the size of the charcoal ranges from 8 to 10 mesh. 
   
   
       8 . The method as claimed in  claim 1 , wherein an inert gas is used in the fluidized bed furnace as a carrier gas with a circular flow of 2˜4 l/min. 
   
   
       9 . The method as claimed in  claim 8 , wherein the circular flow of the inert gas is 3 l/min. 
   
   
       10 . The method as claimed in  claim 1 , wherein the temperature of the carburizing agent ranges from 930 to 1000° C. 
   
   
       11 . The method as claimed in  claim 1 , wherein the period ranges from 5 to 30 minutes. 
   
   
       12 . The method as claimed in  claim 1 , wherein the weight ratio of the charcoal to the carbonate salt powder is 9:1.