Characterization of hard coatings - Part I: DLC coatings

Diamond-like carbon (DLC) coatings is a special group of hard coating that are often used in automotive industry in low friction applications (piston rings) or in tool industry (endmills, drill bits or molds). DLC coatings are also used in many other applications for reduction of wear and abrasion. This application report demonstrates the use of indentation, scratch and tribology for complete characterization of this type of coatings.

Diamond-like coatings (DLC) are today one of the most often used coatings for improvement of mechanical frictional and tribological performance of many components and parts [1, 2]. The diamond-like
carbon term comprises different types of coatings or films whose structure is formed by amorphous carbon.

The main types of DLCs are:
▪ hydrogen free diamond-like carbon (commonly referred to as a-C),
▪ tetrahedral amorphous carbon (ta-C),
▪ hydrogenated tetrahedral amorphous carbon (ta-C:H).

Included as DLC coatings are also amorphous carbon films that contain small amounts of dopants such as metals. The DLC coatings are usually deposited either by Physical Vapor Deposition (PVD) or by Chemical
Vapor Deposition (CVD), in some cases with plasma enhancement (PECVD). The typical thickness of the DLC films is in the range of several micrometers although some DLC films can be as thin as several tens of nanometers.

This application report summarizes the use of indentation, scratch, tribology and coating thickness measurements for a complete characterization of mechanical properties, adhesion and thickness of DLC coatings.

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