In recent years, a new generation of coatings has developed strongly, with considerable commercial success. These Diamond-Like Carbon (DLC) coatings present the advantage of possessing high hardness (1,500 -3,200 HV) but also a coefficient of friction much lower than that of conventional hard layers such as TiN, TiCN, etc. (5 to 10 times lower).
This unique combination of properties has opened up new possibilities, permitting the improvement of technical parts like engine components, etc. Moreover, these coatings are generally bio- compatible and therefore suitable for food contact and medical applications.
So as to meet the various operating conditions encountered by technical components used for automotive and other generic industrial applications, HEF has developed a range of DLC coatings capable of meeting all friction reduction requirements.
HEF is thus heavily involved in the development of technologies aimed at reducing fuel consumption and CO2 emissions in the automotive industry, the solutions developed by HEF now being used by engine manufacturers worldwide for the improvement of friction:
• In rocker arm systems
• In mobile coupling systems
• In transmission systems
These coatings generally comprise several layers of various materials such as Cr, CrN, Si, W and WC- C combined with a top layer of amorphous carbon enriched or not with hydrogen.
The selection of the sub-layer is based on several factors such as the adherence requirements, the wear mode, the type of contact, the friction regimes encountered during operation, the load applied and other metallurgical considerations.
These coatings offer a unique combination of high hardness and low coefficient of friction, compared with the conventional PVD coating (TiN, CrN, AlTiN, etc.) and soft coatings (such as solid lubricants: molybdenum disulphide).
HEF is a leading supplier of tribological coatings and has a wide range of solutions. On account of control of processes and materials and its tribology expertise, the HEF Group has, moreover, the ability to adapt its coatings to suit specific requirements.
Some of the most common commercial variants of HEF's DLC coatings are indicated below.
| Coatings | Architecture | Thickness | Hardness* | Treatment temperature | Maximum use temperature* | Coefficient of friction(dry)* | Applications |
|---|---|---|---|---|---|---|---|
| Certess™DT | a-C:H Metal doped |
Generally 2-4 µm Adaptable to suit the application |
1000-1500Hv | 150 - 350°C depending on substrate |
350°C | 0,20 - 0,25 | Adhesive wear resistance of mechanical parts Automotive components, dry lubrication |
| Certess™DCX | Cr,N + a-C:H | Généralement 2-4 µm Adaptable to suit the application |
Generally 2000-2200Hv Complete range: 1000-2800Hv |
150 - 350°C depending on substrate |
350°C | 0,11 - 0,15 | Abrasive wear resistance of mechanical parts in heavily loaded contacts, Reduction of friction losses for automotive components |
| Certess™DCY | Cr + WCC + a-C:H | Généralement 2-4 µm Adaptable to suit the application |
Generally 2000-2200Hv Complete range: 1000-2800Hv |
150 - 350°C depending on substrate |
350°C | 0,11 - 0,15 | Abrasive wear resistance of mechanical parts in heavily loaded contacts, Reduction of friction losses for automotive components |
| Certess™DCZ | CrN + WCC + a-C:H | Généralement 2-4 µm Adaptable to suit the application |
Generally 2000-2200Hv Complete range: 1000-2800Hv |
150 - 350°C depending on substrate |
350°C | 0,11 - 0,15 | Abrasive wear resistance of mechanical parts in heavily loaded contacts, Reduction of friction losses for automotive components |
