Methods of forming a superhard structure or body comprising a body of polycrystalline diamond containing material

Abstract

A method of producing a free standing PCD comprises forming a mass of combined diamond particles and precursor compound(s) for the metals of the metallic network by suspending the diamond particles in a liquid, and crystallising and/or precipitating the precursor compounds in the liquid. The mass is then removed from suspension by sedimentation and/or evaporation to form a dry powder of combined diamond particles and precursor compound(s). The powder is subjected to a heat treatment to dissociate and reduce the precursor compound(s) to form metal particles smaller in size than the diamond particles to provide a homogeneous mass. This is then consolidated using isostatic compaction to form a homogeneous cohesive green body of a pre-selected size and 3-dimensional shape. The green body is subjected to high pressure and high temperature conditions such that the metallic material wholly or in part becomes molten and facilitates diamond particle to particle bonding via partial diamond re-crystallisation to form a free standing PCD body.

1 . A method of producing a free standing PCD body comprising a combination of intergrown diamond grains forming a diamond network and an interpenetrating metallic network, not attached to a second body or substrate made of a different material such as a metal, cermet or ceramic, the method comprising the steps of:
 a. forming a mass of combined diamond particles and precursor compound(s) for the metals of the metallic network by suspending the diamond particles in a liquid, and crystallising and/or precipitating the precursor compounds in the liquid;   b. removing the mass from suspension by sedimentation and/or evaporation to form a dry powder of combined diamond particles and precursor compound(s);   c. subjecting the powder to a heat treatment to dissociate and reduce the precursor compound(s) to form metal particles smaller in size than the diamond particles to provide a homogeneous mass;   d. consolidating the homogeneous mass of diamond particles and metallic material using isostatic compaction to form a homogeneous cohesive green body of a pre-selected size and 3-dimensional shape; and   e. subjecting the green body to high pressure and high temperature conditions such that the metallic material wholly or in part becomes molten and facilitates diamond particle to particle bonding via partial diamond re-crystallisation to form a free standing PCD body; wherein:   the diamond network of the PCD body is formed of diamond grains having a plurality of grain sizes, the diamond network comprising a grain size distribution having an average diamond grain size, wherein the largest component of the diamond grain size distribution is no greater than three times the average diamond grain size; and   the PCD material forming the free standing PCD body is homogeneous, the PCD body being spatially constant and invariant with respect to diamond network to metallic network volume ratio, wherein the homogeneity is measured at a scale greater than ten times the average grain size and spans the dimension of the PCD body, the PCD material being macroscopically residual stress free at said scale.   
     
     
         2 . A method according to  claim 1  wherein the mass of combined diamond particles and precursor compound(s) for the metals of the metallic network is formed by simultaneously or sequentially adding to the suspension a solution of a metal containing compound and a solution of a reactive compound such that an insoluble precursor compound(s) for the metal(s) of the metallic network nucleates and grows on the surfaces of the diamond particles forming the precursor compound(s) as particles attached to and decorating the diamond particle surfaces. 
     
     
         3 . A method according to  claim 1  wherein the mass of combined diamond particles and precursor compound(s) for the metals of the metallic network is formed by crystallizing from solution in the suspending liquid a soluble precursor compound(s) for the metals of the metallic network. 
     
     
         4 . A method according to  claim 2  wherein the precursor compound(s) for the metal of the metallic network is (are) crystallized and/or precipitated in a suspension of pre-selected portion of the diamond particles; the method further comprising after completion of the crystallization and/or precipitation of the precursor compound(s) adding the remaining portion of the diamond particles to the stirred suspension prior to removal of the suspension liquid; and subsequently applying heat treatment to dissociate and/or reduce the precursor compound(s) to metallic particles. 
     
     
         5 . A method according to  claim 4  wherein the portion of diamond particles for initial combination with the precursor compound(s) is pre-selected on the basis of diamond particle size and/or diamond mass proportion. 
     
     
         6 - 8 . (canceled) 
     
     
         9 . A method according to  claim 1 , wherein the liquid suspension medium is water or an alcohol. 
     
     
         10 . (canceled) 
     
     
         11 . A method according to  claim 2 , wherein the precursor compound(s) is (are) a carbonate, hydroxide, oxalate or acetate. 
     
     
         12 . A method according to  claim 3 , wherein the precursor compound(s) is a nitrate. 
     
     
         13 - 15 . (canceled) 
     
     
         16 . A method according to  claim 2 , wherein the precursor compound(s) is (are) selected from tungstates, molybdates, tantalates, titanates, niobates, vanadates and stannates. 
     
     
         17 - 18 . (canceled) 
     
     
         19 . A method according to  claim 2  wherein the precursor is an amorphous semi-porous oxide. 
     
     
         20 . A method according to  claim 19  wherein the oxide is selected to be any one or more of or any permutation of tungstic oxide, WO 3 , molybdic oxide, MoO 3 , tantalum pentoxide, Ta 2 O 5 , titanium oxide, TiO 2 , niobium pentoxide, Nb 2 O 5 , and vanadium oxide, V 2 O 3 . 
     
     
         21 . A method according to  claim 20  wherein the reactant compound to form the oxide by reaction with water is an alcoxide of general formula M(ROH) n , M being a metal and R being an organic alkane. 
     
     
         22 . A method according to  claim 2 , wherein the mass of diamond particles and precursor compound(s) is heated in a reducing gas environment to convert the precursor compound(s) to metallic particles smaller than the diamond particles. 
     
     
         23 . A method according to  claim 22  wherein the gaseous environment contains hydrogen. 
     
     
         24 . A method according to  claim 22 , wherein the temperature and time of heat treatment is sufficient to generate amorphous non-diamond carbon where metallic particles decorate and are attached to the diamond surfaces and/or are in contact with the diamond surfaces. 
     
     
         25 . A method according to  claim 22 , wherein the temperature and time of heat treatment is insufficient to generate amorphous non-diamond carbon where metallic particles decorate and are attached to the diamond surfaces and/or are in contact with the diamond surfaces. 
     
     
         26 . A method according to  claim 2 , wherein one or more of the precursor compound(s) yields one or more transition metal carbides at the surface of the diamond particles during heat treatment. 
     
     
         27 . A method according to  claim 26  wherein the precursor compound(s) yield a metal/metal carbide combination attached to the diamond surfaces. 
     
     
         28 . A method according to  claim 27  where the metal/metal carbide combination is selected from cobalt/tungsten carbide, cobalt/tantalum carbide or nickel/titanium carbide or any combination. 
     
     
         29 . A method according to  claim 1  wherein the green body is subjected to a pressure in the range of 5 to 10 GPa and to a temperature in the range 1100 to 2500° C. to form a fully dense free standing PCD body. 
     
     
         30 - 31 . (canceled)