Diamond, our abrasive

The word Diamond comes from the ancient Greek word Adàmas, which means “indomitable, invincible”; in fact Diamond is the hardest mineral known, and in ancient Greece times there was no other material able to scratch or notch it. The Romans then gave the name Adamàs to steel, the hardest metal then known; it is a curious coincidence how the two meanings of the same word would have met two thousand years later.

 

diamante

from left synthetic diamond – CBN

 

The reason of Diamond’s extreme hardness resides in its cubic crystalline structure, very compact because consisting only of small Carbon atoms arranged tetrahedrally and building very strong bonds with adjacent atoms. This crystalline form in nature is obtained from coal subjected to extremely high pressure and temperature at very high depth under the earth crust, emerging then towards the surface through volcanic pipes; this is the reason why Diamond mines are typically chimney-shaped.

For more than a century man has tried in vain to replicate those extreme conditions to be able to manufacture synthetic Diamonds, until in 1941 General Electric started the Diamond Project: the plan is to use Graphite (the other crystalline form of Carbon, with hexagonal structure) and apply a temperature of 2-3000°C and a pressure of 50-100.000bar, using Nickel, iron and Cobal catalysts. GE synthetizes in this way the first industrial Diamonds in February 1955, launching them on the market in 1958.

Curiously, graphite is a more stable crystalline form of Carbon than Diamond, so the famous words “Diamonds are forever” are not true, since in a few million years all Diamonds will become graphite.

Diamond has been successfully used for grinding carbide since the ‘50s, but there is a major limitation in its use with steel and cast iron, since iron reacts with carbon, compromising the stability of Diamond crystals. Steel and cast iron have been machined with conventional abrasives (Aluminum Oxide and Silicon Carbide) until the ‘70s, when again General Electric synthetizes CBN, marketed with the name Borazon.

CBN is developed starting from a compact crystalline structure with strong bonds as Diamond, but without Carbon; to achieve that Boron Nitride is chosen: it is a molecule made of Boron and Nitrogen, the two elements next to Carbon, one lighter and the other heavier. The cubic crystalline form of Boron Nitride is CBN (Cubic boron Nitride), whose hardness is about half of Diamonds’ but still twice as Aluminum Oxide and Silicon Carbide; this is why Diamond and CBN are called superabrasives, to differentiate them from conventional abrasives.

During the ‘70s also Polycristalline Diamond and CBN become available: to synthetize those products even more extreme temperature and pressure conditions are necessary, usually achieved in detonation chambers inside abandoned caves. In this way Diamond and CBN micro-grains made of microcrystalline particles are sintered on a carbide backing.
CAFRO has always been a pioneer in the Diamond and CBN wheels’ and tools industry, manufacturing natural Diamond wheels even before synthetic Diamond was available. We have been among the first users of synthetic Diamond first and then CBN, and the first manufacturers in Italy of Polycrystalline Diamond and CBN tools.

CAFRO is today synonym with Diamond for many of our customers: high quality, strong bond with our customers, clarity and solidity are our fundamental features, stemming from the abrasive that is following us from our very first steps.

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