Method of manufacturing a diamond film/coating cutting tool

Abstract

In order to provide an excellent toughness and a sufficient adhesive force without any limit in the content of other carbides in the substrate material and Co and in the size of the cemented carbides grains, the present invention provides a diamond film coated cutting tool, comprising a surface layer which cemented carbide grains are grown abnormally on the cemented carbide substrate, and a diamond film formed on the surface layer, and also a method for manufacturing a diamond film coated cutting tool, comprising the steps of heat-treating a surface of a cemented carbide substrate under a decarburizing atmosphere until the surface changes to a η phase, heat-treating the surface-decarburized cemented carbide substrate under a carburized atmosphere, depositing a diamond film on the carburized surface of the cemented carbide substrate.

What is claimed is:  
     
         1 . A diamond film coated cutting tool, comprising: 
 a surface layer which cemented carbide grains are grown abnormally on the cemented carbide substrate; and    a diamond film formed on the surface layer.    
     
     
         2 . The tool of  claim 1 , wherein said cemented carbide substrate is one selected from the group consisting of WC group, TiC group, and TaC group.  
     
     
         3 . The tool of  claim 1 , wherein said cemented carbide surface contains Co below 16 wt %.  
     
     
         4 . The tool of  claim 1 , wherein said cemented carbide substrate contains other carbides below 20 wt %.  
     
     
         5 . The tool of  claim 1 , wherein a thickness of the abnomally grain-grown layer is 5˜15 μm.  
     
     
         6 . The tool of  claim 1 , wherein a thickness of the diamond film is in a range of 10˜100 μm.  
     
     
         7 . A method for manufacturing a diamond film coated cutting tool, comprising the steps of 
 heat-treating a surface of a cemented carbide substrate under a decarburizing atmosphere until the surface changes to a η phase;    heat-treating the surface-decarburized cemented carbide substrate under a carburized atmosphere; and    depositing a diamond film on the carburized surface of the cemented carbide substrate.    
     
     
         8 . The method of  claim 7 , further comprising a step of pre-treating the surface of the cemented carbide substrate using a diamond powder after the carburizing heat-treating step.  
     
     
         9 . The method of  claim 7 , wherein said decarburization and carburization heat-treating steps are performed at a temperature between 1300 to 1500° C.  
     
     
         10 . The method of  claim 7 , wherein said decarburization and carburization heat-treating steps are performed between 0.1 torr to normal pressure.  
     
     
         11 . The method of  claim 7 , wherein said decarburization heat-treating step is performed under a vacuum atmosphere, a hydrogen atmosphere or an oxygen atmosphere.  
     
     
         12 . The method of  claim 7 , wherein said carburized heat-treating step is performed under a hydrocarbon atmosphere.