FUTURE GRAIN DEVELOPMENTS

Research is accelerating both in existing alumina-based grain technology and in new ultra-hard materials. In the group of ceramic-processed alumina materials, Saint-Gobain released SG in 1986 [U. S. Patent 4,623,364] followed by extruded SG in 1991 [U. S. Patent 5,009,676]. More recently in 1993, Treibacher released an alumina material with hard filler additives [U. S. Patent 5,194,073]. Electrofused technology has also advanced. Pechiney produced an Al-O-N grain (Abral) produced by the cofusion of alumina and AlON followed by slow solidification. It offered much higher thermal corrosion resistance relative to regular alumina while also having constant self-sharpening characteristics akin to ceramic-processed materials but softer acting [Roquefeuil 2001].

New materials have also been announced with hardness approaching CBN and diamond. Iowa State University announced in 2000 an Al-Mg-B material with a hardness value comparable to CBN [U. S. Patent 6,099.605]. Dow Chemical patented in 2000 an Al-C-N material with a hardness value close to diamond [U. S. Patent 6,042,627]. In 1992, the University of California patented some — C3N4 and — C3N4 materials that may actually be harder than diamond [U. S. Patent 5,110,679]. Whether any of these materials eventually proves to have useful abrasive properties and can be produced in commercial quantities has yet to be seen. Nevertheless, there will undoubtedly be considerable advances in abrasive materials in the coming years.

5.8 postscript

In the short time since this chapter was first prepared the superabrasives market has seen dramatic change. GE Superabrasives is no longer owned by GE and has been renamed Diamond Innovations. De Beers has moved much of its European manufacturing to South Africa and renamed its Industrial

Division, Element 6. Chinese manufacturers, as of 2005, have increased their superabrasive grain capacity to over 4 billion carats/annum creating a market excess and further driving down prices. It is expected that in the coming years this will accelerate the conversion of large production wheels from alox to CBN grain for high production applications such as through-feed centerless and plunge grinding. It will also ensure the continuance of the ongoing battle between the competing technol­ogies of hard turning and grinding.