cryogenic hardening is a cryogenic treatment process where the material is slowly cooled to very low temperatures. by using liquid nitrogen, the temperature can go as low as −196 °c. it can have a profound effect on the mechanical properties of certain materials, such as steels or tungsten carbide. in tungsten carbide (wc-co), the crystal structure of cobalt is transformed from softer fcc to harder hcp phase whereas the hard tungsten carbide particle is unaffected by the treatment.