Superhard constructions and methods of making same

A method of forming a super hard polycrystalline diamond construction comprising:

• forming a pre-sinter assembly comprising:
• a first mass of diamond grains or particles;
• a second mass of diamond grains or particles;
• the first mass of diamond grains in having an average grain size between around 1.5 to around 10 times an average grain size of the diamond grains in the second mass;
• and
• a substrate;
• the method further comprising the steps of:
• treating the pre-sinter assembly at an ultra-high pressure of around 5 GPa or greater and a temperature to bond together the diamond grains to form a body of interbonded polycrystalline diamond grains bonded to the substrate, the first mass forming a first fraction comprising around 5 vol % to around 30 vol % of the diamond grains in the body;
• and
• the second mass forms a second fraction comprising from about 70 vol % to about 95 vol % of the diamond grains in the body;
• the method further comprising treating the polycrystalline diamond construction to remove accessible residual catalyst/binder material from at least some interstitial spaces between the interbonded polycrystalline diamond grains wherein the body has at least one region forming a thermally stable region having at most 3 weight percent of catalyst material for diamond.