Synthetically produced grit materials have replaced natural abrasives in a wide range of applications. The most important synthetic grit materials are:
• corundum (Al2O3),
• silicon carbide (SiC),
• cubic boron nitride (cBN) and
• (synthetic) diamond.
Corundum and silicon carbide belong to the conventional grinding materials, while cBN and diamond represent the superabrasive category. An overview of the hardness and fracture toughness of these grit materials is provided in Fig. 3-1.
The higher performance of superabrasives compared with conventional grit materials is already clear from this figure. With conventional grit materials, performance enhancements are possible by means of newly developed sintered corundum (e. g. sol-gel corundum). Although the hardness of the grit material is higher than the material to be processed, the toughness of the abrasive is much lower. It is therefore evident that further performance enhancements can be achieved by developing new grit materials with extremely high hardness and sufficient toughness [HELL93]. For comparative purposes, the hardness and toughness domain of materials processed by grinding, such as tool steel, high speed steel (HSS) and carbide, are also shown in Fig. 3-1.