Boronizing or Boriding is a method of hardening, in which steel is heated in a bath containing compounds of boron, called boriding mixture. 

Boron carbide is commonly used in the boriding mixture.  The atoms of boron diffuse into the surface of the steel material, hardening it. The boron reacts with the constituents elements in the steel such as iron, nickel and cobalt, forming Iron borides, nickel borides and cobalt borides. 

Boronized metals have high wear resistances and can be used in applications such as drilling and cutting.  Boronizing also makes metals resistant to corrosion.