Polycrystalline diamond structure

A method for making a polycrystalline diamond (PCD) structure, the method comprising:

• providing a first fraction of diamond particles or grains and a sintering additive, the sintering additive comprising a carbon source of nano-sized particles or grains, and forming the diamond particles and sintering additive into a first aggregated mass,
• providing a second fraction of diamond particles or grains and forming into a second aggregated mass;
• consolidating the first aggregated mass and a binder material, typically a catalyst material for diamond and the second aggregated mass to form a green body formed of a plurality of alternating layers or strata of the first and second aggregate masses;
• and subjecting the green body to conditions of pressure and temperature at which diamond is more thermodynamically stable than graphite and for a time sufficient to consume the sintering additive, sintering it and forming a body of polycrystalline diamond material that is:
• thermodynamically and crystallographically stable,
• substantially devoid of any nano-structures, the body of polycrystalline diamond (PCD) material having a diamond content of at most about 95 percent of the volume of the PCD material, a binder content of at least about 5 percent of the volume of the PCD material,
• the step of sintering further comprising forming a body of polycrystalline diamond material comprising a first region and a second region adjacent the first region, the second region being bonded to the first region by intergrowth of diamond grains;
• the first region comprising a plurality of alternating strata or layers, each stratum or layer having a thickness in the range of around 5 to 300 microns;
• wherein the alternating layers or strata in the first region comprise first layers or strata alternating with second layers or strata, the first layers or strata being in a state of residual compressive stress and the second layers or strata being in a state of residual tensile stress;
• and wherein and one or more of the layers or strata in the first regions and/or the second region comprise diamond grains having a mean diamond grain contiguity of greater than about 60 percent and a standard deviation of less than about 2.2 percent.