Hard metal component with a graduated structure and methods of producing the component

Abstract

A component is produced by powder metallurgy from hard metal. The alloy includes at least one grain growth-inhibiting additive from the group consisting of V, Cr, Ti, Ta and Nb with, at least locally, a graduated concentration profile. As a result, the mechanical properties also have a graduated profile. In the fabrication process, a dispersion or solution which contains the grain growth-inhibiting additive in finely distributed or dissolved form is applied to the surface of a green compact. Penetration of this dispersion or solution along open pores leads to a graduated distribution of the grain growth-inhibiting additive in the green compact. There is also described a process in which the grain growth-inhibiting additive in the form of a solution is distributed uniformly in the green compact and is then gradually broken down from edge regions by a heat treatment or a solvent.

We claim:  
     
         1 . An article of manufacture made from a hard metal alloy, comprising: 
 at least one carbide, mixed carbide or carbonitride of the metals selected from the group consisting of W, Ti, Ta, Mo, Zr, Hf, V, Nb, Cr, and V;    at least one grain growth-inhibiting additive selected from the group consisting of V, Cr, Ti, Ta, and Nb or a compound thereof, at least one of said grain growth-inhibiting additives, at least locally, having a graduated concentration profile; and    at least one metallic binder selected from the group consisting of Co, Ni and Fe with a binder content of 0.1-20% by weight.    
     
     
         2 . The article according to  claim 1 , wherein, at least locally, the hard metal alloy has a graduated grain size profile.  
     
     
         3 . The article according to  claim 1 , wherein, at least locally, the hard metal alloy has a graduated hardness profile.  
     
     
         4 . The article according to  claim 1  formed as a component with an edge zone and a center, and wherein concentration of said grain growth-inhibiting additive decreases gradually from the edge zone of the component toward the center of the component.  
     
     
         5 . The article according to  claim 4 , wherein the carbide grain size increases gradually from the edge zone of the component toward the center of the component.  
     
     
         6 . The article according to  claim 1  formed as a component with an edge zone and a center, and wherein a concentration of said grain growth-inhibiting additive increases gradually from the edge zone of the component toward the center of the component.  
     
     
         7 . The article according to  claim 6 , wherein the carbide grain size decreases gradually from the edge zone of the component toward the center of the component.  
     
     
         8 . The article according to  claim 1 , wherein said grain growth-inhibiting additive consists of at least one metal selected from the group consisting of Cr and V, or a compound thereof, a maximum content of said grain growth-inhibiting additive, based on the hard metal alloy, is 2% by weight, and a content thereof decreases gradually to a value x, where 0<x<1.0% by weight.  
     
     
         9 . A method of producing the component according to  claim 1 , which comprises the following steps: 
 producing a green compact from a hard metal alloy, containing at least one carbide, mixed carbide or carbonitride of the metals selected from the group consisting of W, Ti, Ta, Mo, Zr, Hf, V, Nb, Cr, and V, at least one metallic binder selected from the group consisting of Co, Ni, and Fe, an optional addition of wax or a plasticizer;    producing a dispersion or solution containing at least one grain growth-inhibiting additive selected from the group of metals consisting of V, Cr, Ti, Ta, and Nb or a compound thereof, in finely distributed or dissolved form;    applying the dispersion or solution to a surface of the green compact;    targeted action to establish the concentration gradient; and    subjecting the article to heat consolidation.    
     
     
         10 . The method according to  claim 9 , wherein the step of producing the green compact comprises compacting in a standard powder metallurgy compacting process or shaping in a standard shaping process.  
     
     
         11 . The method according to  claim 9 , wherein the applying step comprises a process selected from the group consisting of dipping, spraying, and brushing.  
     
     
         12 . The method according to  claim 9 , wherein the dispersion or solution is applied only to a partial region of the component surface.  
     
     
         13 . The method according to  claim 9 , wherein the carbidic powder component of the green compact has a mean grain size of <2 μm.  
     
     
         14 . The method according to  claim 9 , which comprises at least partially dewaxing the green compact by a heat treatment step.  
     
     
         15 . A method of producing the component according to  claim 1 , which comprises the following steps: 
 producing a green compact from a hard metal alloy, containing at least one carbide, mixed carbide or carbonitride of the metals selected from the group consisting of W, Ti, Ta, Mo, Zr, Hf, V, Nb, Cr, and V, at least one metallic binder selected from the group consisting of Co, Ni, and Fe, an optional addition of wax or a plasticizer;    producing a solution containing at least one grain growth-inhibiting additive selected from the group of metals consisting of V, Cr, Ti, Ta, and Nb or a compound thereof;    applying the solution to a surface of the green compact;    targeted action to establish the concentration gradient or complete infiltration;    gradually removing the grain growth inhibitor from regions close to the surface by at least one of heat treating and dissolving; and    subjecting the article to heat consolidation.    
     
     
         16 . The method according to  claim 15 , wherein the step of producing the green compact comprises compacting in a standard powder metallurgy compacting process or shaping in a standard shaping process.  
     
     
         17 . The method according to  claim 15 , wherein the applying step comprises a process selected from the group consisting of dipping, spraying, and brushing.  
     
     
         18 . The method according to  claim 15 , wherein the solution is applied only to a partial region of the component surface.  
     
     
         19 . The method according to  claim 15 , wherein the carbidic powder component of the green compact has a mean grain size of <2 μm.  
     
     
         20 . The method according to  claim 15 , which comprises at least partially dewaxing the green compact by a heat treatment step.