Diamond powders and superabrasive grains include extreme-hardness abrasives such as synthetic diamond, natural diamonds, and cubic boron nitride (CBN). They are used in the polishing, finishing, grinding, and cutting of ultra-hard materials such as ceramics, stone, glass, superalloys, and titanium. Diamond powders and superabrasive grains have very high hardness values and are sometimes used in the processing of optics. Natural diamond is the hardest mineral while synthetic diamond is the hardest man-made material. Cubic boron nitride (CBM) is second to diamond in terms of hardness.
Both natural diamond and synthetic diamond are used in many diamond powders and superabrasive grains. Natural diamond is mined from the earth and relatively expensive. Synthetic diamond is produced in a high-temperature, high-pressure process anvil-press. Both natural diamond abrasives and synthetic diamond abrasives are used for grinding non-ferrous metals, ceramics, glass, stone, and building materials. Diamond is not useful in grinding steel or ferrous alloys, however, because carbon or diamond readily dissolves or reacts with iron. In addition, natural diamond and synthetic diamond is susceptible to oxidation at higher temperatures.
Diamond pastes are useful in ferrous polishing or lapping applications where heat and reactivity are not a factor. When selecting diamond powders and superabrasive grains, boort and cubic boron nitride (CBN) are also available. Bort is a very low-grade diamond that is suitable only for industrial use. This poorly-crystallized, dark, and translucent or opaque diamond is also known as boort, boart, and bortz. With hardness second only to diamond, cubic boron nitride has a cubic crystal structure. CBN also provides superior grinding performance on carbon and alloy steel. It is produced synthetically in a high-temperature, high-process anvil-press. The CBN production process is similar to that used for synthetic diamond.
Selecting diamond powders and superabrasive grains requires an analysis of product specifications and features. Basic parameters include application, crystal structure, bond type, and shape and strength. Although application-specification products are available, some diamond powders and superabrasive grains are designated simply for industrial use. There are two choices for crystal structure: single-crystal and polycrystalline. Resin bond and metal bond are common options for bond type. In terms of shape and strength, some diamond powders and superabrasive grains are blocky and strong. Others have sharp angles and a weak shape. High or low friability and coating or treatment options are features to consider.