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DLC - Type ta-C

Tetrahedral amorphous carbon (ta-C): an evolution of Diamond Like Carbon (DLC) for applications under extreme stress.

The development of new engines that are required to meet strict environmental standards has led to the latest technological advanced concepts and new surface treatments.
HEFGROUPE, one of the world leaders in surface engineering, has unparalleled knowledge in powertrain optimization thanks to its DLC (Diamond Like Carbon) deposition solutions.
Due to their unique mechanical properties and chemical inertia, DLC coatings significantly reduce friction losses, wear and seizure risks, regardless of the lubricant characteristics.
Currently the majority of DLC solutions proposed for lubricated mechanical contacts are hydrogenated amorphous carbon (a-C:H) layers, which under extreme stress have restrictions (temperature, load, oxidizing atmosphere,...).
These limitations can be overcome thanks to the use of amorphous tetrahedral carbon (ta-C) layers, thus making it possible to keep up with the latest and most severe technical developments whilst preserving the exclusive properties of DLC.

Although a-C:H and ta-C belong to the same material family, they are not produced by the same coating process.
a-C:H is achieved by PECVD (Plasma Enhanced Chemical Vapor deposition) in a gaseous environment.
Whereas, ta-C is produced by PVD-arc (Physical Vapor deposition arc) from a solid carbon target.
PVD-arc technology enables the production of a ta-C coating with a higher percentage of sp3 hybridization without hydrogen and providing a higher hardness.
For each coating, HEFGROUPE has developed a patented plug n’ play source that can be used in our highly productive, robust, in-house manufactured coating equipment.
This strategy is a real advantage to be able to produce the latest version of each coating with optimal reliability and competitive prices.

At HEF GROUPE , we are not only coating specialist but also experts in tribology. Extensive research work allows us to confirm that:
In lubricated conditions, the two coatings exhibit the same level of friction due to two main characteristics of DLC :

  • Roughness of DLC decreases continuously in use.
  • Chemical inertia regarding oil additives.

Due to a higher percentage of sp3 and no hydrogen, ta-C coating provides an:

  • Increased resistance to abrasive wear
  • Increased resistance to tribo-chemical wear
  • Wider range of use for the pressure/temperature pair

However, with ta-C:

  • Higher stresses result in a lower coating thickness
  • It is impossible to treat parts with complex geometry due to the need for re-polishing after deposition

Within HEF GROUPE , both technical solutions are available worldwide with the same level of quality.
We give our clients the freedom to choose the most appropriate solution to their problems.
See below a subjective rating between a-C:H and ta-C for lubricated contacts.