Composition of PCD
Polycrystalline Diamond (PCD) is a synthetic diamond product that is produced by sintering together selected diamond particles with a metal matrix using sophisticated technology. The diamond and matrix, when sintered together under high temperatures and pressures, creates a PCD tool blank that is high in uniform hardness and is abrasive resistant in all directions. This PCD diamond layer is then bonded to a tungsten carbide substrate, which provides strength and a brazable base to permit bonding to other metals.
Polycrystalline tipped tools are exceptionally resistant to wear compared to tungsten carbide or ceramic tools. In certain applications, PCD tool life can exceed carbide cutting tool life 50 to 100 times.
In certain applications, polycrystalline tipped tools have several advantages over natural diamond.
SHOCK RESISTANCE: PCD is more shock resistant over natural diamond because of its random orientation structure of the diamond particles, and is backed by a carbide substrate.
CONSISTENCY: PCD is more constant in wear. Again because of the random orientation of diamond particles. Natural diamond is a single crystal in nature and has soft and hard grains. Depending on the shape of the natural diamonds and the tool being manufactured, it is sometimes not practical to have hardest grain on the cutting edge.
AVAILABILITY: PCD is readily available in a large variety of shapes and sizes. Discs as large as 50mm in diameter are now available. Natural diamond is limited to what is formed in nature. Diamond, even with only an 8mm long cutting edge is extremely difficult to find and is very costly.
COST: PCD blank costs are considerably lower than the costs of natural diamond stones, and the availability of different shape PCD blanks reduce manufacturing cost significantly. The longer of a cutting edge required, the larger the savings of PCD over natural diamond due to the rarity of larger stones.
Natural diamond and PCD diamond compliment each other. Natural diamond is denser than its PCD counterpart and consequently can be polished to a keener cutting edge.
Natural diamond is best suited to produce very fine finishes and precise tolerances as required in the manufacturing of jewelry, plastic contact lens, computer memory discs, and aluminum camera parts.
Polycrystalline diamond tooling can be used in a wide range of machining operations such as milling, grooving, turning, facing and boring. They are recommended for machining non ferrous metals and abrasive non metallics.
Materials recommended for cutting with PCD:
Aluminum and aluminum alloys
Copper, brass and bronze alloys
Zinc and magnesium alloys
Gold and silver
Tungsten carbide, presintered and sintered
Carbon and graphite
Plastics and rubber
Chipboard and fibreboard
PCD cutting tools are available in various grades, depending on the application.
Composition of CBN
Cubic boron nitride (CBN) is an artificially synthesized material exceeded in hardness only by diamond. Unlike diamond, however, CBN is stable under conditions of high temperature (up to 1000° C) normally seen when machining hardened ferrous or super alloy materials.
Like polycrystalline diamond, CBN is available in a large variety of shapes and sizes. Discs are available up to 42mm diameter. CBN is also available is several different grades, depending on the application.
CBN tools permit metal cutting at feeds and speeds much higher than conventional cutting tools materials. CBN tools are also being used to turn, bore and face hard materials, which previously could be formed only by grinding. Because CBN tools maintain a sharp cutting edge, part surface finishes are excellent, close tolerances are easy to maintain, and dramatic productivity increases can be expected.
Materials recommended for cutting with CBN:
Alloy steels (45-68 RC)
Carbon tools steels (45-68 RC)
Die Steel (45-68 RC)
High speed steel (45-68 RC)
Chilled cast iron
Moly chrome steel rolls