Polycrystalline superhard material and method for making same
A method of making a body of polycrystalline superhard material comprising placing an aggregated mass of grains of superhard material into a canister, placing a ceramic layer either in direct contact with the aggregated mass of grains of superhard material or in indirect contact therewith, the ceramic layer being spaced from the grains by an interlayer of material when present, 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 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 aggregated mass of grains of superhard material and ceramic layer are subjected to a pressure of greater than 5.5 GPa and sintered to form a body of polycrystalline superhard material having a surface topology complementary to the surface topology of the ceramic layer. The ceramic layer and interlayer if present are then removed from the body of polycrystalline material. There is also disclosed a body of polycrystalline superhard material having a surface topology on a first surface, the first surface being substantially free of material from a canister used in formation of the body of polycrystalline superhard material.
1. A method of making a body of polycrystalline superhard material comprising:
placing an aggregated mass of grains of superhard material into a canister;
placing a ceramic layer formed of a ceramic material in indirect contact with the aggregated mass of grains of superhard material, 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 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 from the body of polycrystalline material.
2. A method according to claim 1 , 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.
3. A method according to claim 1 , wherein the step of subjecting the grains of superhard material to a pressure comprises subjecting the grains to a pressure of greater than 7 GPa.
4. A method according to claim 1 , wherein the grains comprise grains of diamond material and 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.
5. A method according to claim 4 , 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.
6. A method according to claim 1 , wherein the 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 material.
7. A method according to claim 1 , wherein the step of placing an aggregated mass of grains of superhard material into a canister comprises placing an aggregated mass of natural or synthetic diamond grains into the canister.
8. A method according to claim 1 , wherein the step of placing an aggregated mass of grains of superhard material into a canister comprises placing an aggregated mass of cubic boron nitride grains into the canister.
9. A method as claimed in claim 1 , further comprising treating the body of super-hard material to remove catalyst material from interstices between inter-bonded grains in the superhard material after sintering.
10. A method according to claim 1 , further comprising constructing the surface topology of the ceramic material to impart a chamfered edge to the body of polycrystalline superhard material during sintering.