Diamond Characterization

Current Technological Breakthroughs

Since the introduction of manufactured diamond in 1957, numerous new products have evolved offering end users increased quality and productivity. The evolution of new superabrasive products continues today to even better serve the material removal market. For example, consistent diamond quality is a requirement for consistent tool performance. Without greatly improved manufacturing consistency, lot-to-lot diamond characteristics can change enough that tools may fail. The cause of this type of failure is often impossible to determine. Until recently, saw diamond was characterized only by its resistance to chipping (friability). It is well known that specification of diamond by friability alone is not sufficient to exclude changes in diamond that can lead to tool failure.

Consequently, in 1992, GE embarked on an extensive technical program to better define and control diamond properties. The breakthrough came in 1994 with a complete definition of diamond shape and a method to control shape during diamond manufacture to assure shape consistency. The shape of saw diamond can be characterized by two features: typical crystal morphology and deviations from this ideal morphology. Crystal morphology generally is cubo-octahedral.

Image analysis techniques, developed for GE's Aerospace business group to allow computers to interpret satellite photographs, were adapted to measure diamond crystal morphology.

However, very few saw diamonds are perfectly cubo-octahedral due to elongation of an axis, surface roughness, and/or chipped edges or corners. Research has shown that these deviations can be characterized by eccentricity. It has long been known that diamond shape affects tool performance. However, that shape was only evaluated subjectively by visual observation. Even experts often disagreed in their visual evaluations of shape. In order to specify and control shape in diamond products, the shape characteristics had to be quantified, i.e. numbers assigned to them. This required analytical methods to reliably and rapidly measure morphology and eccentricity.

This critical problem was overcome when GE adapted computer technology, originally developed for its aerospace operations, to measure with precise numbers the shape statistics of large populations of crystals. The proprietary computer program measures not only where the population falls on the cubo-octahedral scale, designated as tau (t), but also the eccentricity. GE Superabrasives now uses this computer system in its saw diamond products to assure, for the first time, products with consistent shape characteristics.

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