Polycrystalline diamond construction and method of making

Abstract

A superhard polycrystalline construction comprises a body of polycrystalline superhard material, comprising a mass of superhard grains exhibiting inter-granular bonding and defining a plurality of interstitial regions therebetween, the superhard grains having an associated mean free path and a non-superhard phase at least partially filling a plurality of the interstitial regions and having an associated mean free path. The median of the mean free path associated with the non-superhard phase divided by (Q3−Q1) for the non-superhard phase being greater than or equal to 0.50, where Q1 is the first quartile and Q3 is the third quartile; and the median of the mean free path associated with the superhard grains divided by (Q3−Q1) for the superhard grains being less than 0.60. The body of polycrystalline superhard material has a first surface having a surface topology comprising one or more indentations therein and/or projections therefrom. There is also disclosed a method of forming such a construction.

1 . A superhard polycrystalline construction comprising a body of polycrystalline superhard material, comprising:
 a mass of superhard grains exhibiting inter-granular bonding and defining a plurality of interstitial regions therebetween, the superhard grains having an associated mean free path; and   a non-superhard phase at least partially filling a plurality of the interstitial regions and having an associated mean free path;   the median of the mean free path associated with the non-superhard phase divided by (Q3−Q1) for the non-superhard phase being greater than or equal to 0.50, where Q1 is the first quartile and Q3 is the third quartile; and   the median of the mean free path associated with the superhard grains divided by (Q3−Q1) for the superhard grains being less than 0.60;   wherein the body of polycrystalline superhard material has a first surface having a surface topology comprising one or more indentations therein and/or projections therefrom.   
     
     
         2 . A superhard polycrystalline construction according to  claim 1 , wherein the superhard grains comprise natural and/or synthetic diamond grains, the superhard polycrystalline construction forming a polycrystalline diamond construction. 
     
     
         3 . A superhard polycrystalline construction according to  claim 1 , wherein the non-superhard phase comprises a binder phase. 
     
     
         4 . A superhard polycrystalline construction according to  claim 3 , wherein the binder phase comprises cobalt, and/or one or more other iron group elements, or an alloy thereof, and/or one or more carbides, nitrides, borides, and oxides of the metals of Groups IV-VI in the periodic table. 
     
     
         5 . A superhard polycrystalline construction according to  claim 4 , wherein the one or more other iron group elements comprises iron or nickel. 
     
     
         6 - 7 . (canceled) 
     
     
         8 . A superhard polycrystalline construction according to  claim 1 , wherein the first surface comprises an external working surface forming the working or cutting surface of the polycrystalline construction in use. 
     
     
         9 . A superhard polycrystalline construction according to  claim 1 , wherein the polycrystalline construction comprises one or more of:
 up to 20 wt % nanodiamond additions in the form of nanodiamond powder grains;   salts;   borides or metal carbides of at least one of Ti, V, or Nb; or   at least one of the metals Pd or Ni.   
     
     
         10 . A superhard polycrystalline construction as claimed in  claim 1 , wherein at least a portion of the body of polycrystalline superhard material is substantially free of a catalyst material for diamond, said portion forming a thermally stable region. 
     
     
         11 . A superhard polycrystalline construction as claimed in  claim 10 , wherein the thermally stable region extends a depth of at least 50 microns from a surface of the body of polycrystalline superhard material. 
     
     
         12 . A superhard polycrystalline construction as claimed in  claim 10 , wherein the thermally stable region comprising at most 2 weight percent of catalyst material for diamond. 
     
     
         13 . (canceled) 
     
     
         14 . A superhard polycrystalline construction as claimed in  claim 1  wherein the median of the mean free path associated with the non-superhard phase divided by (Q3−Q1) for the non-superhard phase being greater than or equal to 0.83. 
     
     
         15 . A superhard polycrystalline construction as claimed in  claim 1  wherein the median of the mean free path associated with the superhard grains divided by (Q3−Q1) for the superhard grains is less than 0.47. 
     
     
         16 . A superhard polycrystalline construction according to  claim 1 , wherein the first surface is substantially free of material from a canister used in formation of the body of polycrystalline superhard material. 
     
     
         17 . The polycrystalline superhard construction according to  claim 16 , wherein the first surface is of the same quality as the bulk of the body of polycrystalline superhard material. 
     
     
         18 - 22 . (canceled) 
     
     
         23 . An insert for a machine tool, comprising a cutter structure joined to an insert base, the cutter structure comprising the polycrystalline superhard construction as claimed in  claim 1 , the surface topology being formed on a first face of the body of polycrystalline superhard material, the first surface forming a rake face or a cutting face, and the surface topology of the first surface forming chip-breaker topology. 
     
     
         24 - 25 . (canceled) 
     
     
         26 . A method of forming a superhard polycrystalline construction, comprising:
 providing a mass of grains of superhard material; and   treating the pre-sinter assembly in the presence of a catalyst/solvent material for the superhard grains at an ultra-high pressure of around 5.5 GPa or greater and a temperature at which the superhard material is more thermodynamically stable than graphite to sinter together the grains of superhard material to form a polycrystalline superhard construction, the superhard grains exhibiting inter-granular bonding and defining a plurality of interstitial regions therebetween, a non-superhard phase at least partially filling a plurality of the interstitial regions;   wherein:   the median of the mean free path associated with the non-superhard phase divided by (Q3−Q1) for the non-superhard phase is greater than or equal to 0.50, where Q1 is the first quartile and Q3 is the third quartile of the mean free path measurements associated with the non-superhard phase; and   the median of the mean free path associated with the superhard grains divided by (Q3−Q1) for the superhard grains is less than 0.60, where Q1 is the first quartile and Q3 is the third quartile of the mean free path measurements associated with the superhard grains; and   the method further comprising forming a non-planar surface topology in a first surface of the body of polycrystalline diamond material, the surface topology comprising one or more indentations in and/or projections extending from the first surface.   
     
     
         27 . The method of  claim 26 , wherein, the step of providing a mass of grains of superhard material comprises providing a mass of diamond grains having a first fraction having a first average size and a second fraction having a second average size, the first fraction having an average grain size ranging from about 10 to 60 microns, and the second fraction having an average grain size less than the size of the first fraction. 
     
     
         28 - 38 . (canceled) 
     
     
         39 . The method of  claim 26 , wherein the step of forming the surface topology comprises:
 placing an aggregated mass of grains of superhard material into a canister;   
       placing a ceramic layer formed of a ceramic material either in direct contact with the aggregated mass of grains of superhard material, or in indirect contact therewith wherein the ceramic layer is spaced from the grains by an interlayer of material, the ceramic layer having a surface with surface topology, the surface topology imprinting a pattern in the aggregated mass of grains of superhard material complementary to the surface topology, the ceramic material and the material of the interlayer where present being such that they do not react chemically with the superhard material and/or a sinter catalyst material for the grains of superhard material; the method further comprising:
 subjecting the aggregated mass of grains of superhard material and ceramic layer to a pressure of greater than around 5.5 GPa in the presence of the sinter catalyst material for the grains of superhard material at a temperature sufficiently high for the catalyst material to melt; sintering the grains to form a body of polycrystalline superhard material having a surface topology complementary to the surface topology of the ceramic layer; and 
 removing the ceramic layer and said interlayer if present from the body of polycrystalline material. 
 
     
     
         40 . A method according to  claim 39 , wherein the step of placing the ceramic layer in contact with the grains of superhard material comprises placing the ceramic material in indirect contact therewith through the interlayer of material, the interlayer comprising a coating on the ceramic layer. 
     
     
         41 . (canceled) 
     
     
         42 . A method according to  claim 39 , wherein the step of placing the ceramic material in contact with the grains comprises placing a ceramic material formed of any one or more of the group of oxide ceramic materials that are not reduced by carbo-thermal reaction in contact with the grains. 
     
     
         43 . A method according to  claim 42 , wherein the ceramic material is formed of any one or more of the group of oxide ceramic materials comprising magnesia, calcia, zirconia, and/or alumina. 
     
     
         44 - 45 . (canceled) 
     
     
         46 . A method according to  claim 39 , wherein step of forming the body of polycrystalline superhard material comprises forming a body having a free outer surface on removal of the ceramic layer therefrom in which the free outer surface is of the same quality as the bulk of the body of polycrystalline superhard material. 
     
     
         47 - 48 . (canceled) 
     
     
         49 . A method according to  claim 39 , wherein the step of placing the mass of superhard grains into a canister comprises placing an aggregated mass of natural or synthetic diamond grains into the canister. 
     
     
         50 - 51 . (canceled) 
     
     
         52 . A method as claimed in  claim 26 , further comprising treating the body of superhard polycrystalline material to remove catalyst material from interstices between inter-bonded grains in the superhard material after sintering. 
     
     
         53 - 56 . (canceled)