A widely used method of case-hardening steel that
eliminates scaling and the tendency to
decarburisation and results in clean components.
Sodium cyanide is the common media for this
process, usually heated within the range of
900-930 deg C. It is advisable to pre-heat the
components in neutral salts to avoid a temperature
drop resulting from immersing cold components into
the cyanide. After carburising, either single quench
hardening or refining and hardening and tempering
is carried out.