Boron Carbide: (B4C)

Boron Carbide B4C is one of the hardest materials known, ranking third behind diamond and cubic boron nitride. It has varied uses like below

Boron Carbide (B₄C) sandblasting nozzles

Boron Carbide (B₄C) for antioxidant additives in magnesia-carbon bricks (MgO-carbon bricks) in Refractories

Boron Carbide powder (B₄C) for lapping and polishing in abrasives>

Boron Carbide (B₄C) armor tiles in military applications