Diamond Products for Metallography

Kemet Diamond Products are available in Standard grade, manufactured with Monocrystalline Diamond Powder, or in our SUPERIOR Premier grade, manufactured with Polycrystalline Diamond Powder. For Kemet Standard and Premier Grades only the highest quality virgin Diamond Powder is used, which must satisfy two important criteria - shaping and grading.

Kemet Standard Grade is manufactured with quality Monocrystalline Diamond Powder, matching the shape and size required to offer rapid stock removal and quality surface finish.

The spherical ‘blocky’ shape of Polycrystalline Diamond contains a greater number of cutting facets than Monocrystalline Diamond, giving significant improvements in performance.

  • Highest material removal rates.
  • Finest surface finish.
  • Reduced sub-surface damage.
  • Particularly recommended for polishing ceramics, sintered materials, and composites containing different materials.

Monocrystalline

Monocrystalline Natural and synthetic are very similar in structure. Synthetic diamond is manufactured by copying conditions occurring in nature when natural diamonds were formed millions of years ago. Intense heat and pressure deep in the earth (2000Km) caused the structure of carbon graphite to change to diamond. To manufacture synthetic diamond, graphite is loaded into a special capsule together with a catalyst such as iron or nickel. This is placed in a hydraulic press and subjected to extremely high temperature (1500 C) and pressure (60 tons/cm2). Under these conditions graphite is converted into monocrystalline synthetic diamond.

Monocrystalline diamond contains a single crystal structure, which has distinct cleavage planes causing the diamond to fracture under stress. This can result in deeper vertical micro scratching on certain materials which is either tolerated or can take longer to polish out

monocrystalline structure

Polycrystalline

The method of synthesis is quite different from monocrystaline. Graphite is sealed in a tube which is placed in a larger heavier tube. The tube assembly is taken deep into a mine and surrounded with high velocity explosives. The explosion collapses the tube subjecting the graphite to enormous pressures - up to 7 Million PSI. The shock changes graphite to polycrystalline diamond which contains thousands of small particles about 1/100 µ in size, bonded together in random fashion.

Polycrystalline diamond has much smaller cleavage planes which causes only surface microfractures. The random structure gives polycrystalline diamond toughness in all directions resulting in less sub-surface damage. Polycrystalline diamond gives faster stock removal and better surface finish especially on harder materials than monocrystalline. The greatest difference in performance is with the finer micron sizes.

Polycrystalline structure

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