Classification and Application of Super Abrasives

Ⅰ. The types of super abrasives

1. Diamond

(1) Natural diamond: It is the crystal of cubic crystal system formed under the high temperature and high pressure inside the earth. It is the hardest among the naturally formed minerals. Its Knoop hardness reaches 7000. It will chemically react with iron and nickel at high temperature. So it is not suitable for the grinding of iron-based metals.

(2) Synthetic diamond: an artificial product formed under high temperature and high pressure with carbon powder and metal catalyst which can be made into synthetic diamond powder.

(3) Metal-plated synthetic diamond: the above-mentioned diamond is plated with Ni, Cu and other metals.

2. CBN

(1) Cubic boron nitride: an artificial product formed under high temperature and high pressure by adding a metal catalyst to hexagonal boron nitride. It has the same crystal structure as diamond, with a Knoop hardness of 4700. It can remain stable even at high temperatures, so cbn powder is mostly used for grinding steel materials.

(2) Metal-plated cubic boron nitride: the above-mentioned CBN is plated with Ni, Ti compounds and other substances.

Different from general abrasives, the entire grinding wheel can be composed of abrasives and adhesives. Because super abrasives have higher cost and strong cutting force (cutting force is 2 to 5 times that of general abrasives), the consumption of super abrasives is also less. There is only one layer of abrasive on the outermost ring, and the center is made of metal or ceramic.

Ⅱ. The characteristics of super abrasives

The high hardness of super grit abrasives does not mean it is omnipotent. Because different abrasives have different characteristics, in principle, alumina is suitable for workpieces with high tensile strength, and WA is used when the contact area between the grinding wheel and the workpiece is large. Silicon carbide is suitable for workpieces with low tensile strength, and the workpiece is hard and brittle. GC is used when the contact area between the material or the grinding wheel and the workpiece is large. Diamond (D) or cubic boron nitride (CBN) is used for materials that are particularly difficult to cut.