PVD coatings are already used for some automotive components with great success. For example, there is almost no Diesel passenger car without PVD coatings to provide wear protection in the injection system and there is no Formula 1 race without such coatings. Wear protection and more recently reduction of friction to reduce internal losses in the engine will further increase the demand for PVD coatings in future to develop the so called one liter car (consumption of 1 liter per 100 km, or about 200 miles per gallon).

In this paper, first an overview of today’s coatings and their application in series products are given. As in many cases today not the technical performance however the production (coating) costs are the limitations to use PVD in series cars, cost calculations are presented and technical attempts are discussed to reduce manufacturing costs in total.

Tribological coatings are an ever evolving component to a coatings supplier’s portfolio . Research and development in this area should be conducted by first evaluating the contact (tribological) characteristics and then translating that information to ideal coating properties. With this set of desirable properties a supplier can see which coating would make the best match or what can be modified in order to make that match.

Regarding the choice of coatings, several parameters play a dominant role. It is important to differentiate between rolling, sliding, or mixed mode conditions. Also, the heat treatment conditions, the grinding operation after heat treatment and the resulting surface quality (e.g. roughness) of both contact partners should be taken in consideration. Post-treatments of vacuum deposited coatings are necessary in several occasions in order to avoid running-in failure modes.

The drawback of a-C:H coatings ("DLC") is the sensitivity to crack initiation and crack propagation. Adequate support from base material, heat treatment, and base layers by PVD can avoid such cracking issues.

The ongoing push for higher fuel efficiency, lower emission rates, higher power densities, lighter base materials, and longer warranty periods are drivers to increase the demand for surface enhancements of individual automotive components. The coatings prove their technical value, but the main challenge is to offer such coatings on an acceptable cost level.

So called dual core coatings consist of metal carbide or nitride supporting layer beneath a carbon based hard layer, i.e. diamond like carbon. This type of coating stack is widely used in automotive applications due to its superior performance. The main objective of this work was to obtain a CrC layer with good mechanical and tribological properties that can be applied to create an improved supporting layer for DLC coatings.

In a first step CrC films were synthesized by reactive magnetron sputtering from a pure chromium target in a reactive Ar/C₂H₂ gas mixture onto steel and silicon samples. The influence of numerous deposition parameters was evaluated from results of layer characteristics such as hardness, adhesion and friction combined with XRD and REM measurements, as well as process analysis with a mass spectrometer. Layers with hardness up to 2700 HV_pl and still keeping friction at a low value to sustain a good wear reserve were produced. Adding a PECVD diamond like carbon layer on top of CrC layer improved performance which is shown by measurements of wear resistance and SRV tests.

The overall results show a promising future for creating a reproducible process of a CrC-DLC coating with a supporting layer of high tribological performance and hardness.

Thin diamond-like carbon films and other carbon containing coatings are nowadays widely used in automotive applications like e.g. Diesel injection. The main role of these coatings is to reduce wear and friction of the components but today each application has its own tailored layer structure and composition adapted to the customer specifications.

This paper investigates the role of different carbon concentrations in the gas phase with respect to sliding and wear properties of the coatings. The deposition technique for the carbon based hard coatings is a PVD/PECVD process described in detail elsewhere [1]. For a specific carbon source measurements of partial pressures of carbon containing molecules have been carried out using a quadropole mass spectrometer. The comparison of sliding and wear properties for different carbon concentrations during deposition has been carried out by means of ball on disc test, SRV measurements and calo grinding under defined parameters.

[1] EP1362931: Method and apparatus for fabrication of a DLC layer system