... of the hardest materials known, ranking second behind diamond. Boron carbide is characterized as following,Extreme hardness,hardness 9.36. ... abrasive and wear resistance, sealed washer (gasket), and the nozzles for water jet cutters, slurry pumping, grit blashing, etc. ... generate tremendous amount of heat in combination with oxygen, boron carbide is used as rocket propellant in aerospace industry. It ...