What is DLC?
Diamond-Like Carbon, commonly referred to as DLC, is a family of carbon-based coatings that has extreme hardness due to the diamond crystal (tetragonal) structure and is soft and lubricious due to the graphite crystal (hexagonal) structure. DLC is amorphous in nature (does not have a crystal structure. DLC is a technological advancement of Physical Vapor Deposition (PVD) + Plasma Enhanced Chemical Vapor Deposition (PECVD) coatings that has been widely successful in the commercial industry.

Is DLC a type of PVD coating?
DLC coatings are deposited using a Plasma Assisted Chemical Vapor Deposition (PACVD) method. Unlike the PVD method which involves physically depositing the solid target material source onto the component surface, PACVD involves a precursor gas source (hydrocarbon) that is broken down into carbon and hydrogen atoms in plasma and deposited as DLC on the component surface in an amorphous fashion.

Is DLC directly applied to component surfaces?
DLC coatings are generally applied after a PVD underlayer such as Titanium (Ti), Chromium (Cr) or Chromium Nitride (CrN), or a combination has first been deposited on the component surface. The selected underlayer depends on various factors such as hardness of the component surface (substrate), bonding characteristics with the substrate, load bearing requirements of the application, and is determined based on the application and performance requirements.

What is a typical deposition temperature for DLC coatings?
DLC coatings are deposited at relatively low temperatures below 200°C. Calico’s technology allows these coatings to be applied at around 170°C. With our plasma enhancement technology, we can deposit at these low temperatures, ensuring there is no distortion or change in core properties of the component being coated. Thus, precision components with tight dimensional tolerances can be coated with DLC without any concerns.

What is the general DLC coating thickness range?
Total coating thickness, including underlayer, is uniform and ranges from 1 to 5 microns. The exact coating thickness within this range is determined based on the application and performance requirements.

What is the hardness of DLC coatings?
DLC coating hardness can range from 1500 - 3200 HV, depending on the type of DLC coating and choice of underlayer.

What are the main benefits of DLC coatings?

• High hardness (2500-4500 HV)
• Excellent wear resistance
• Friction reduction
• Thin, uniform film (precision coating)
• Excellent aesthetics

What is a typical friction coefficient value achieved with DLC coatings?
Coefficient of friction is generally the ratio of the frictional force to the normal force when two bodies interact with each other. Applying DLC coatings helps to reduce friction for applications involving smooth, interacting surfaces. Lubrication plays a key role in this property as well. Typical friction coefficient range for components with DLC coated surfaces can be around 0.10 to 0.25 in a dry-condition and less than 0.10 in a lubricated condition.

Are there any limitations of DLC coatings?
DLC coatings, primarily due to carbon, cannot be used when service temperatures exceed 350°C.

Can you remove the DLC coating and re-coat components if required?
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 amount of time. The components may require additional polishing before recoating.

Are there different types of DLC coatings?
DLC is a family of ultra-hard, thin-film, carbon-based coatings that can be broadly classified into:

Hydrogenated DLC, represented as a-C:H (amorphous carbon, hydrogenated). In this category there are several coatings with different underlayers – but all have the same a-C:H top layer. The full range of hardness for coatings within this family is 1000-2800 HV, but the typical range is 2000-2200 HV. For further details, please refer to the DLC Coatings section of our website.

Non-Hydrogenated DLC, represented as ta-C (tetrahedral amorphous carbon). This coating is deposited from solid carbon sources, rather than a gaseous hydrocarbon (as for the a-C:H coatings) precursor. The specific arrangements of the carbon atoms within the ta-C coatings results in them being at least 20% harder than the standard a-C:H coatings and can withstand operating temperatures of up to 450° C – which is about 100° C higher than the maximum temperature resistance of a-C:H coatings.

What are typical applications of DLC Coatings?
DLC coatings are used for a wide range of applications. DLC coatings are especially useful where a combination of both wear and friction reduction is required. DLC coatings also offer a cosmetically pleasing charcoal finish. Typical applications include:

• Automotive: piston wrist lifters, pins, rocker arms, transmission gears, etc.
• Medical: surgical tools, prosthetic applications
• Firearms: pistol slides, barrels, bolt carriers
• Industrial components and machinery: pistons, plungers, gears, mechanical seals
• Injection molding: dies, ejector pins, sliding machine parts