Method of producing a tool for cutting, drilling or crushing of solid material, and such a tool

Abstract

A tool for cutting, drilling or crushing of solid material, wherein the tool includes a cemented carbide body attached to a steel holder by a braze joint located between a base surface of the cemented carbide body and the steel holder. The cemented carbide body has a hard phase mainly of tungsten carbide, WC, and a binder consisting of cobalt, wherein the cobalt content of the cemented carbide body is equal to or lower than about 5.5 wt %. The cemented carbide body has a cobalt content gradient therein wherein the cobalt content increases towards the base surface and is at least 4.5 wt % at the base surface. The ratio of the cobalt content at the base surface to the cobalt content of the cemented carbide is ≥1.09. A method for producing the tool is also presented.

1 . A method of producing a tool for cutting, drilling or crushing of solid material, said tool including a cemented carbide body attached to a steel holder, wherein said method comprises the steps of:
 providing a cemented carbide body by providing a powder mixture, compacting said powder mixture into a compact having a hard phase of tungsten carbide, WC, and a binder of cobalt, wherein the cobalt content of the compact is at a first cobalt content level and is ≤about 5.5 wt %;   providing a compound including a carbide or a nitride formed by carbon or nitrogen and an element that has a grain growth inhibiting effect on tungsten carbide, and providing an element that has a grain growth promoting effect on WC;   applying said compound and said grain growth promoting element onto at least a tip region of said compact, wherein said tip region will form a tip region of the cemented carbide body arranged for engagement with material to be cut, drilled into or crushed by said tool, and keeping a base surface of the compact, which will form a base surface of the cemented carbide body that will be attached to said steel holder, free from said compound and grain growth promoting element, wherein said compound and said grain growth promoting element is of a type that will diffuse into the compact in connection to sintering of the latter and thereby will induce a generation of a cobalt content gradient in the sintered compact, with an increasing cobalt content in a direction away from a surface onto which said compound and said grain growth promoting element has been applied;   sintering the compact provided with said compound and said grain growth promoting element into said cemented carbide body, the cobalt content at said base surface being a second cobalt content level that is ≥4.5 wt % as a result of said induced generation of a cobalt content gradient, wherein the ratio of the second cobalt content level to the first cobalt content level is ≥1.09; and   attaching said base surface of the cemented carbide body to the steel holder by brazing.   
     
     
         2 . The method according to  claim 1 , wherein the second cobalt content at said base surface is ≥5.0 wt %. 
     
     
         3 . The method according to  claim 1 , wherein the second cobalt content at said base surface is ≥6.0 wt %. 
     
     
         4 . The method according to  claim 1 , wherein the ratio of the second cobalt content level to the first cobalt content level is ≥1.14. 
     
     
         5 . The method according to  claim 1 , wherein said tip region of the cemented carbide body has a mean cobalt content, being a third cobalt content level of ≤4.5 wt %. 
     
     
         6 . The method according to  claim 5 , wherein the ratio of the second cobalt content level to the third cobalt content level is ≥1.2. 
     
     
         7 . The method according to  claim 1 , wherein the first cobalt content level is ≤about 5.0 wt %. 
     
     
         8 . The method according to  claim 1 , wherein said compact includes top and lateral surfaces and said base surface, and that said compound and said grain growth promoting element is applied to at least 50% of the total area of the top and lateral surfaces. 
     
     
         9 . The method according to  claim 1 , wherein said compact includes top and lateral surfaces and wherein, in a zone of the lateral surface or surfaces neighbouring the base surface, the lateral surface or surfaces are excluded from the application of said compound and said grain growth promoting element. 
     
     
         10 . The method according to  claim 1 , wherein said compact includes top and lateral surfaces and said base surface, and wherein a distance between the top surface and the base surface, which is opposed to the top surface, is less than 25 mm, and wherein said compound and said grain growth promoting element are applied onto at least a part of said top surface. 
     
     
         11 . The method according to  claim 1 , wherein, in said compound, the element that has a grain growth inhibiting effect on WC is any of chromium, vanadium, tantalum or niobium and said grain growth promoting element is carbon in the form of graphite. 
     
     
         12 . A tool for cutting, drilling or crushing of solid material, comprising:
 a cemented carbide body attached to a steel holder by a braze joint located between a base surface of the cemented carbide body and the steel holder, said cemented carbide body having a hard phase of tungsten carbide, WC, and a binder consisting of cobalt, wherein the cobalt content of the cemented carbide body is at a first cobalt content level and is equal to or lower than about 5.5 wt %, and wherein, the cemented carbide body has a cobalt content gradient therein wherein the cobalt content increases from a tip region towards said base surface, the base surface having a second cobalt content level that is at least 4.5 wt %, wherein the second ratio cobalt content level to first cobalt content level is ≥1.09.   
     
     
         13 . The tool according to  claim 12 , wherein the second cobalt content level is at least 5.0 wt % at said base surface of the cemented carbide body. 
     
     
         14 . The tool according to  claim 12 , wherein the second cobalt content level is at least 6 wt % at said base surface of the cemented carbide body. 
     
     
         15 . The tool according to  claim 12 , wherein the ratio second cobalt content level to first cobalt content level is ≥1.14. 
     
     
         16 . The tool according to  claim 12 , wherein said tip region of the cemented carbide body has a mean cobalt content having a third cobalt content level of ≤4.5 wt %. 
     
     
         17 . The tool according to  claim 16 , wherein the ratio of the second cobalt content level to the third cobalt content level is ≥1.2. 
     
     
         18 . The tool according to  claim 12 , wherein the cobalt content of the cemented carbide body, being the first cobalt content level, is ≤about 5.0 wt %. 
     
     
         19 . The tool according to  claim 12 , wherein said cemented carbide body has a generally knob-like shape, has a generally circular bottom surface with a diameter d, and has a height h, wherein 0.5<h/d<2, and said bottom surface defines said base surface. 
     
     
         20 . The tool according to  claim 12 , wherein said cemented carbide body has a generally plate-like shape, has width w, a height h and a thickness t, and wherein 0.2<h/w<2, t<w, 1.7 mm<t<17 mm, and, said base surface being a large side of said body, and wherein said tip region includes at least a part of an opposite large side thereof. 
     
     
         21 . The tool according  claim 12 , wherein at least in the tip region thereof, the cemented carbide body has an outer surface zone having an elevated WC mean grain size as a result of an elevated content of an element that has a grain growth promoting effect on WC, and a second zone below said outer surface zone, wherein, in said second zone, the WC mean grain size is smaller than in said outer surface zone as a result of an elevated content therein of an element that has a grain growth inhibiting effect on WC, and wherein the cemented carbide body has the cobalt content gradient therein as a result of the presence of said grain growth promoting element and said grain growth inhibiting element therein.