- Borazon
Borazon, a
boron nitride allotrope , is the fourth hardest substance, afteraggregated diamond nanorods ,ultrahard fullerite , anddiamond , and the third hardest artificial material. Borazon is acrystal created by heating equal quantities ofboron andnitrogen at temperatures greater than 1800 °C (3300 °F) at 7 GPa (1million lbf/in²). Borazon is the only substance other than those listed above that can scratch a diamond [http://biotsavart.tripod.com/bci.htm] (althoughlasers can cut diamond). A diamond will also scratch Borazon.Borazon was first produced in
1957 byRobert H. Wentorf, Jr. , a physical chemist working for theGeneral Electric Company . In1969 , General Electric adopted the name Borazon as itstrademark for the crystal.Uses and production
Prior to the production of Borazon, also referred to as cubic boron nitride or CBN,
diamond was the preferred abrasive used for grinding very hardsuperalloys but it could not be used effectively onsteel s because of its carbon solubility potential.Aluminium oxide was the conventional abrasive used on hardened steel tools. [http://www.patentstorm.us/patents/5308367-description.html Description of Borazon and Borozon as prior art in patent from 31 December 1969] ]Borazon replaced aluminium oxide for grinding hardened steels due to its far superior abrasive properties, comparable to that of diamond. Borazon is used in industrial applications to shape tools, as it can withstand temperatures greater than 2000 °C (3500 °F), much higher than that of a pure diamond at 871 °C (1600 °F).Fact|date=April 2008 Other uses include
jewellery designing,glass cutting and laceration of diamonds.Fact|date=April 2008CBN-coated grinding wheels, referred to as Borozon wheels, are routinely used in the machining of hard ferrous metals, cast irons, and nickel-base and cobalt-base superalloys. They can grind more material, to a higher degree of accuracy, than any other abrasive. The limiting factor in the life of such tools is typically determined not by wear on the cutting surface but by its break-down and separation from the metal core resulting from failure of the bonding layer.
ee also
*
Boron nitride
*Abrasives
*Abrasive machining References
External links
* [http://www.winstonbrill.com/bril001/html/article_index/articles/51-100/article61_body.html Discovering a Material That's Harder Than Diamond] by
Robert H. Wentorf, Jr.
* [http://biotsavart.tripod.com/bci.htm Boron in Materials Technology]
* [http://www.abrasivesnet.com/en/product/mbs/cbn/index.htm Borazon-CBN]
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