DLC stands for Diamond-Like Carbon. This is a special family of thin-film coatings that provide the high hardness like diamond (due to its tetragonal structure) and low lubricity like graphite (due to its hexagonal structure). DLC though, is amorphous in nature i.e. it does not have a crystal structure, however, offers combined advantages in spite of its overall random arrangement of carbon atoms.
DLC coatings are deposited using a Plasma Assisted Chemical Vapor Deposition (PACVD) method. Unlike PVD method that involves physically depositing the solid target material source on the component surface, PACVD on the other hand involves a precursor gas source (hydrocarbon) that is broken down into carbon and hydrogen atoms in plasma, deposited as DLC on the component surface in an amorphous fashion.
DLC coatings are generally applied after a PVD underlayer such as Ti, Cr, CrN or WCC or a combination of them has first been deposited on the component surface. The selection of the underlayer depends on various factors such as hardness of the component surface (substrate), bonding characteristics with the substrate, load bearing requirements of the application, etc. The choice of underlayer is determined case by case primarily based on the application and performance requirements.
DLC coatings are deposited at relatively low temperatures below 200°C. HEF’s specific deposition technology allows us to deposit these coatings at around 170°C. With our plasma enhancement technology, HEF is able to deposit at such low temperatures to ensure no distortion or change in core properties of the component being coated. Thus, precision components with tight dimensional tolerances can be DLC coated without any concerns.
Total coating thickness including the underlayer is uniform and generally in the range of 2 to 5 microns. The exact coating thickness within this range is determined based on the application and performance requirement.
DLC coating hardness can range from 2500 HV to 4500 HV depending on the type of DLC coating including the choice of underlayer.
DLC coatings offer the following benefits
Coefficient of friction is a system property. It is generally the ratio of the frictional force to the normal force when two bodies interact with each other. Deposition of DLC coatings helps with friction reduction of the system for applications involving smooth, interacting surfaces. Lubrication plays a key role in this property as well. Typical friction coefficient range for such systems with DLC coated surfaces can be around 0.1 to 0.2 in a dry-condition and less than 0.1 in a lubricated condition.
DLC coatings, primarily due to carbon, cannot be used when service temperatures exceed 350°C.
Yes. DLC coating can be removed or stripped if required. While the DLC layer can be removed within the same coating chamber using a reactive plasma-based process, removal of the PVD underlayer(s) requires components to be immersed in a chemical solution for a certain time period. The components may require additional polishing before recoating. This is generally discussed with the customer on a case-by-case basis. HEF has the capabilities to offer these services, if required.
DLC is a family of ultra-hard, thin-film, carbon-based coatings that can be broadly classified into:
DLC coatings are used for many of the applications that have been highlighted for PVD coatings, in general – except for cutting tools which are exposed to high operating temperatures. DLC coatings are especially useful where a combination of both wear and friction reduction is required. DLC coatings also offer a cosmetically pleasing black finish. Typical applications include:
CERTESS® CARBON is a tradename of HEF Group for DLC coatings. Depending on your application, there are different options that can be provided within the family of CERTESS® CARBON coatings. Some of these include:
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