| 摘要 |
A superhard polycrystalline construction or PCD 30 comprises a first region 34 with body of thermally stable polycrystalline superhard material having an exposed surface forming a working surface 4, a peripheral side edge 6, a second region forming a substrate 32 to the first region and a third region 36 at least partially interposed between first and second regions. The third region comprises a material more acid resistant than polycrystalline diamond material having a cobalt binder-catalyst phase, and/or more acid resistant than cemented carbide. The third region may extend to and form part of the working surface. The superhard construction may have a fracture toughness between 4 MPa√m to around 15 MPa√m. The first region may have a peripheral surface extending around at least a portion of the peripheral outer surface of the third region. The third region may comprise a ceramic material, refractory metal or a cermet material. The refractory metal may include any one or more of: niobium, molybdenum, tantalum, tungsten, rhenium, titanium, vanadium, chromium, zirconium, hafnium, ruthenium, osmium or iridium. The superhard construction may be for a shear or percussion or rolling cone drill bit or cutter or reamer or expandable tool. |
