is a cryogenic heat treating
process where the material is cooled to approximately , usually using liquid nitrogen
. It can have a profound effect on the mechanical properties of certain steels
, provided their composition and prior heat treatment are such that they retain some austenite
at room temperature. It is designed to increase the amount of martensite
in the steel's crystal structure, increasing its strength
, sometimes at the cost of toughness
. Presently this treatment is being practiced over tool steels, high-carbon, and high-chromium steels to obtain excellent wear resistance. Recent research shows that there is precipitation of fine carbides (eta carbides) in the matrix during this treatment which imparts very high wear resistance to the steels.
The transformation from austenite to martensite is mostly accomplished through quenching
, but in general it is driven farther and farther toward completion as temperature decreases. In higher-alloy steels such as austenitic stainless steel
, the onset of transformation can require temperatures much lower than room temperature. More commonly, an incomplete transformation occurs in the initial quench, so that cryogenic treatments merely enhance the effects of prior quenching.
The transformation between these phases is instantaneous and not at all... Read More