Why is boron carbide used as an abrasive?

Boron carbide ($B_{4}C$) is utilized as an abrasive primarily because it is one of the hardest synthetic substances known to science. With a Mohs hardness rating between 9 and 10, its extreme hardness allows it to effectively perform the lapping—or fine abrading—of various metal and ceramic products.12

While it is highly effective for these applications, it is important to note that its utility as an abrasive is limited by its thermal properties. Because it has a relatively low oxidation temperature of 400–500° C (750–930° F), it cannot withstand the high heat generated during the grinding of hardened tool steels. Beyond its use as an abrasive, the material's hardness and low density also make it valuable for wear-resistant applications, such as sandblasting nozzles and pump seals.1