FUNDAMENTAL CHANGES

Non-ferrous metals and plastic

DCT allows the molecules to reposition themselves. The more compact molecular structure and improved molecular binding achieved results in greater toughness and strength, a smoother surface and improved conductivity.

Ferrous metals

Cryogenic treatment results in two changes to the microstructure of steel.

During the initial heat treatment the steel is very rapidly cooled in order to induce martensite to form. The temperature at which austenite converts into martensite (also termed Mf) is dependant on the carbon content and the alloying elements in the steel. By adding alloying elements the properties of the material are improved but the Mf value is markedly reduced. This is often to a temperature of the cooling medium that is used during the initial heat treatment. The extremely low temperatures employed in the process thus ensures the DCT completes the forming of the martensite. After the transformation process the material is tempered and the martensite will be stabilised to form a tougher structure.

Eta-carbide forming

During the long submersion in liquid nitrogen (LN2) carbon clusters develop in the newly formed martensite. This in turn ensure that fine eta-carbide can be precipitated during the second stage of the treatment process.

Due to these fine particles or “fillers” (indicated in the above photographs) a more compact, more coherent and stronger matrix is formed with the large carbide particles that are already present in the material.

In situations where wear occurs the martensite and the fine eta-carbide formations work together. The carbide particles help to support the martensite matrix so that it is harder for pieces of material to break away. When a small hard part is crushed against the surface of the material the carbide matrix offers resistance against distortion and thus wear is also reduced.

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