Deep Cryogenic Treatment or Cryo Treating is a one-time permanent process that toughens most ferrous and non-ferrous materials. Examples would be metals, metallic alloys, carbides, aluminium, bronze and brass to name but a few. Unlike a surface treatment, Deep Cryogenic Treatment toughens the material right through to the core. In addition to increased wear, impact and fatigue resistance, materials are relieved of most residual stresses.

Deep Cryogenic Treatment (DCT) may be oversimplified into a process of chilling a part down to near absolute zero and maintaining that condition until the material has cold soaked.
The temperature is then allowed to rise until ambient equilibrium is reached. The
part may then be subjected to a normal tempering reheat, although this step is not always included in the process.

The complexity of the process involves determining and achieving the proper duration for the cooling, soaking, and warming cycles. It is here that developments in computer modelling and controls have placed cryogenic treatment on the cutting edge of metal treatment.

The Science
Cryogenics is the treatment of materials at extremely low temperatures. For ferrous steels, sub-zero treatment at temperatures of approximately –80°C transforms retained austenite left by the heat treatment process to martensite (martensite is 4 times harder than austenite). During this transformation additional smaller carbide particles are released and evenly distributed through the material resulting in reduced residual stresses and a very hard, fine carbide lattice structure.

Deep cryogenic treatment at temperatures in excess of –185°C further enhances the materials properties. By slowing down atomic movement, the internal molecular bonding energy is increased which promotes a pure structural balance throughout the mass of the material. The end result is a material that has an extremely uniform, refined and dense microstructure with vastly improved properties.

The Equipment
We own and operate the most comprehensive Cryogenic facilities in Europe including three distinct levels of advanced cooling apparatus, a combination of liquid Nitrogen and Helium processing capability in tandem with multi stage in house tempering systems means we cover the broadest commercial DCT temperature range available to the market.
Our treatment chamber is of stainless steel construction, and up to the most demanding load requirements. And unlike other chambers on the market, ours is a dual purpose unit that also performs the tempering phase, so there is never any disruption to the components during processing.

We utilise computer technology to control the entire process; from the ramp down through to the controlled changes in temperature levels right through to the heat tempering phase. In 2010 we have invested in a significant computer technology innovation that has allowed better process control as well as amazingly consistent results.

Our Experience
We have been established since 1998, it pains us to think back of those early years with the masses of research and development, experimenting and testing to find just the right formula for the very best results.

From our research and development we have developed a range of specific “recipes” which are utilised appropriately depending on the composition of material treated.

The Process
One of the most important steps for deep cryogenic treatment to be effective is process control. When cooling materials the idea is to keep the exterior and interior (core) of the material at the same temperature, thus allowing for the complete transformation of austenite to martensite. Using a microprocessor the components are cooled down at a controlled rate until the material reaches around -196°C – this will vary depending on material.

The material is then “soaked” at deep cryogenic temperatures for a set period. Once the soak is complete the material is then permitted to warm to ambient temperature at a slow controlled rate. When the “soak” is complete the material may require a post temper. The tempering operation is carried out within the same processing chamber or one of our other tempering ovens.

To achieve deep cryogenic temperature levels liquid nitrogen is used. Nitrogen is a non-flammable; non-polluting element, which makes up 80% of the air we breathe, the process, is therefore environmentally friendly and can help companies reduce their Carbon Footprint. Our treatment method is a dry process, so your components never come into direct contact with Liquid Nitrogen. As stated above; for safety reasons Frozen Solid only employs a long soak process on materials thus ensuring a complete transformation of the material and reduces the chances of an embedded matrix within the component being treated.

Read more about the different levels of treatment available in each area we specialise in.

Results

Below is an example of the results from our treatment.
Sample A is a standard blade made from high speed tool steel.
Sample B is the same blade only it has been cryogenically treated by Frozen Solid. Tests on the samples were carried out by an independent laboratory.

         Sample A.                             Sample B.

These were the labs findings:

Sample B. has a more complete martensite transformation than sample A. Sample B has gained a further increase in Rockwell hardness, from 61 HRC to 64 HRC