For those of you who are unfamiliar with the basics of cryo tempering, here is a brief description which starts out easy, then gets a bit more technical as you read further. It should be noted that this custom option is performed at a laboratory here in the United States, and will generally add one to two weeks to your delivery time.

Cryogenic tempering is utilized by most aerospace and large manufacturing concerns to extend the life of metal parts that are subject to abrasion and stress failure. These include NASA, Rockwell Aerospace, General Motors, and even IBM in their production tools.

Basic features and benefits:
Cryo tempering is a permanent, non-destructive, non-damaging process (not a coating) which reduces abrasive wear (edge dulling), relieves internal stress, minimizes the susceptibility to microcracking due to shock forces, lengthens part life, and increases performance. Cryo treated pieces are also less susceptible to corrosion.

There are two basic forms of cryo tempering:
1. Standard cryogenic tempering: which takes about ten hours brings the metal down to a temperature of -120 degrees. This is the process which has been around for some thirty years.
2. Deep cryogenic tempering: which reduces the temperature of the metal to -320 degrees F. There are two sub-catagories of this process, wet and dry. The wet process, although good, has the potential of creating thermal shock to the metal, resulting from the submersion in liquid nitrogen. Last Legend only utilizes what is called the dry process. During this process it takes 9 hours to cool the blades to the target -320 degrees F. They remain at that temperature for thirty hours, at which time an additional 9 hours is utilized to bring the blades back up to room temperature. This process takes a total of 48 hours to perform.

Some stuff sent us by the laboratory: The freezing of metals has been acknowledged for almost thirty years as an effective method for increasing durability, or “wear life”, and decreasing residual stress in steels. The recent field of deep cryogenics (below -300 degrees F) has brought us high-temperature superconductors, the superconducting super collider, cryo-biology, and magneto-hydrodynamic drive systems. It has also brought many additional durability benefits to metals.
The deep cryogenic tempering process is a one-time, permanent treatment affecting the entire part, not just the surface. The metal may be new or used, sharp or dull, and resharpening will not destroy the treatment. The process has a number of obvious benefits, including increases in tensile strength, toughness, and stability through the release of internal stresses. The exceptional increase in wear resistivity, generally exceeding 300%, is the greatest benefit.
A research metallurgist at the National Bureau of Standards states, “When carbon precipitates form, the internal stress in the martensite is reduced, which minimizes the susceptibility to microcracking. The wide distribution of very hard, fine carbides from deep cryogenic treatment also increases wear resistance.” The study concludes, “...fine carbon carbides and resultant tight lattice structures are precipitated from cryogenic treatment. These particles are responsible for the exceptional wear characteristics imparted by the process, due to a denser molecular structure; reducing friction, heat, and wear.” Steel surfaces receiving wear, such as cutters, surgical instruments, gears, drill bits, taps, dies, and racing engines, all benefit from this treatment.
Research has shown that slowly cooling steel to cryogenic temperatures (around -310 degrees F), and soaking the steel at this low temperature for several hours, improves the wear resistance significantly.
There are two main changes in the microstructure of the steel that are caused by cryogenic treatment: First, any retained austenite is transformed into martensite when the material is soaked at very low temperatures. Second, fine carbide particles are formed during the long cryogenic soak.
A Louisiana Tech study looked at how the changes brought about by cryogenic treatment affected steel’s ability to resist abrasive wear. It found that the martensite and fine carbide formed by deep cryogenic treatment work together to reduce abrasive wear. The fine carbide particles support the martensite matrix, making it less likely that micro particles will be dug out of the cutting tool material during a cutting operation and cause abrasion. When a hard asperity or foreign particle is pressed onto the tool’s surface, the carbides further resist wear by preventing the particle from plowing into the surface.
Some of these benefits may be achieved through standard tempering, which also transforms austenite into martensite, but standard tempering will not bring about a complete transformation.