Cryogenically treated materials show a marked increase in many areas:

• Wear resistance

• Toughness

• Eliminates nearly all residual stress

• Dimensional stability

• Fatigue resistance

• Denser microstructure

Improved surface finish and corrosion resistance due to filling of micro holes and micro cracks

Substantial evidence of superior heat transfer

Improved tonal quality in brass instruments and piano/guitar strings

Treated materials become less brittle with little or no change in original hardness unless it was poorly heat treated then a gain of as much as 6 points is possible.

Two main changes in the microstructure of the steel occur as a result of the cryogenic treatment. These changes are the principal reasons for the dramatic improvements.

First, retained austenite (a softer grain structure always present after heat treatment) is transformed into the harder, more durable grain structure martensite. The range of retained austenite can be as high as 50% to as little as 3%. The amount depends on the operator, material being treated, and accuracy of the heat-treating equipment.

Cryogenic treatment simply continues the conversion initiated by the heat treatment, whereby 99.9% or more of the austenite is converted to martensite.

Second, fine eta(n) carbide particles or precipitates are formed during the long cryogenic “soak” (chromium carbides, tungsten carbide, etc.), depending upon the alloying elements in the steel. These are in addition to the larger carbide particles present before the cryogenic treatment. These fine particles or “fillers”, along with the larger particles, form a denser, more coherent, and much tougher matrix in the material.

The surface energy of martensite is higher than the surface energy of austenite due to their own microstructure. In potential adhesive-wear situations, the martensite is less likely to tear out than is austenite. The probability of wear particles forming in a steel in which the austenite has been transformed to martensite is less than for the steel containing excess retained austenite.

In abrasive-wear situations, both the martensite formation and the fine eta(n) carbide formation work together to reduce wear. The additional fine carbide particles help to support the martensite matrix. This makes it more difficult to dig out lumps of the material. When a hard asperity or foreign particle is squeezed onto the surface, the carbide matrix resists plowing and wear is reduced. This is analogous to the fact that concrete made with cement, gravel (large particles) and sand (fine particles) is more resistant to wear and tougher than concrete made with cement and gravel alone.

Almost any kind of tool steel or dynamic part, for whatever application, will exhibit some kind of life increase. As less tools or parts are needed, there is a substantial savings in dollars but that is only part of it. Additional savings in less change over, less maintenance, and less overall down time all lead to lower production costs