Polycrstalline diamond structure

A PCD structure according to any one of the preceding claims, wherein the strata or layers in the second region have a thickness of greater than around 200 microns.

A PCD structure according to any one of the preceding claims, wherein the first region comprises two or more different average diamond grain sizes.

A PCD structure according to any one of the preceding claims, wherein the first region comprises three of more different average diamond grain sizes.

A PCD structure 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 layer or stratum in the first region having a thickness in the range of around 5 to 300 microns;
• the first region comprising two or more different average diamond grain sizes.

A PCD structure 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.

A PCD structure according to any one of the preceding claims, wherein the first region comprises an external working surface forming the initial working surface of the PCD structure in use.

A PCD structure according to any one of the preceding claims, wherein the alternating layers or strata comprise first layers or strata alternating with second layers or strata, the first layers or strata being formed of a diamond mix having three or more different average diamond grain sizes and the second layers or strata being formed of a diamond mix having the same three or more average diamond grain sizes, wherein the first strata or layers in the first region have a different ratio of diamond grain sizes in said mix from the second strata or layers in the first region.

A PCD structure according to any one of the preceding claims, wherein the PCD structure has a longitudinal axis, the layers or strata in the first region and/or the second region lying in a plane substantially perpendicular to the plane through which the longitudinal axis of the PCD structure extends.

A PCD structure according to any one of the preceding claims, wherein the layers or strata are substantially planar, curved, bowed or domed.

A PCD structure according to any one of the preceding claims, wherein the volume of the first region is greater than the volume of the second region.

A PCD structure according to any one of the preceding claims, wherein one or more of the strata or layers intersect a working surface or side surface of the PCD structure.

A PCD structure according to any one of the preceding claims, wherein each strata or layer is formed of one or more respective PCD grades having a TRS of at least 1,000 MPa;

• the PCD grade or grades in adjacent strata or layers having a different coefficient of thermal expansion (CTE).

A PCD element as claimed in any of the preceding claims, wherein at least a portion of the first region is substantially free of a catalyst material for diamond, said portion forming a thermally stable region.

A PCD element for a rotary shear bit for boring into the earth, or for a percussion drill bit, comprising a PCD structure as claimed in any one of the preceding claims bonded to a cemented carbide support body.

A PCD structure substantially as hereinbefore described with reference to any one embodiment as that embodiment is illustrated in the accompanying drawings.