Cryogenic hardening refers to a process of treating metals by cooling them to extremely low temperatures to make them harder and more durable. There are several alternative names for cryogenic hardening, including deep cryogenic treatment, cryogenic processing, and sub-zero treatment. The purpose of cryogenic hardening is to enhance the metal's physical and mechanical properties by making it resistant to wear, corrosion, and other forms of damage. The process is commonly used in the aerospace, automotive, and industrial sectors, among others. Other synonyms for cryogenic hardening include cryo-treatment, cold treatment, and low-temperature hardening, all of which describe the process of treating metals at extremely low temperatures for improved durability.