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DLC TREATED ENGINE BEARINGS

Max Bernardi

23 January 2017

A bearing’s ability to rotate has always been a fundamental aspect. There is a treatment that improves its friction value: DLC. Diamond Like Carbon

In Motorsport, it is well known that details often make the difference and, if you are aiming for victory, nothing must be left to chance. This is also why, in karting, many put their engines in the hands of specialist tuners, who can perform various operations (within the regulations, obviously), both to obtain more power, as well as to improve the rotating ability of components subjected to high engine speeds. With regard to bearings, in particular, a DLC treatment is carried out, which is a coating that uses the two chemical properties of carbon: the typical hardness of diamonds (from which the name "Diamond Like Carbon" originates) and graphite’s ease of sliding.

DLC is an innovative, carbon-based coating that deals with problems related to abrasion, sliding and chemical aggression. Its application to mechanical components of automobile engines is primarily aimed at reducing fuel consumption and thus protecting the environment. The first treatments date back to 2001/2002, initially on heavy vehicles and later on automobiles. This sector, in particular, has prompted more and more research on new, more economic and effective treatment techniques. The main and most exploited characteristic of DLC in this field is its ability to slide: in fact, a reduction in friction and the energy in play results in lower oil consumption and a significant reduction in the emission of pollutants.

In the field of competition, DLC technology appeared in F1 in the Nineties thanks to Jean Todt. The Frenchman used it on Peugeot engines and, subsequently, brought this know-how to Maranello when he became Managing Director of Ferrari F1. In 1996-97, everyone in F1 used DLC coatings, on valves and piston parts.

First of all, you need to remove the bearing (see video), since the treatment is performed on the outer and inner circumference. The process takes place inside a vacuum chamber, which is filled with an ionised gas and brought to a plasma state. In this state, the gas interacts with the surfaces of the bearings, depositing a layer of amorphous carbon. The process is characterised by low deposition temperatures of less than 200° C.

After the coating deposit stage, the bearing takes on a darker, almost black colour. The coating is very adherent and homogeneous, perfectly reproducing the surfaces to be coated. Thicknesses measure up to 4 microns; usually, bearings have a deposit of 3 microns.

The picture, taken through a microscope, shows a section of a material coated in DLC. The material treated has a dark colour and, if we compare the two surfaces, we note the decrease in surface roughness after the treatment.

The treatment reduces the coefficient of friction where ball bearings rotate, significantly improving smoothness. In addition, the material’s strength and, therefore, bearing life and reliability are optimised. DLC coating in karting is not only used on bearings, but also on the coupling axis, which must nevertheless take into account the thickness of the coating in order to maintain the correct tolerances. Various manufacturers have also tested the treatment on the KZ engine transmission, resulting in improved gear shifting times. A negative aspect of the treatment is undoubtedly its cost: few companies are equipped with this type of machinery, despite several fields acknowledging the coating’s versatility.

The light colour shows the material has not been coated. DLC treatment can be repeated several times, always taking into account the tolerances based on the material treated.

While the reduction of friction is one of DLC’s major advantages in racing, other fields can exploit other characteristics. Anti-corrosion: the compactness and amorphous structure of the layer make DLC an excellent barrier against chemical agents. Electrical insulation: a property that derives from the SP3 (diamond) bond. Biocompatibility: when it comes into contact with the human body, a layer of DLC does not cause rejection, does not cause damage, does not generate allergies and does not react with acidic and/or alkaline compounds. All these characteristics greatly increase the possible applications of DLC, in addition to engines, also in other fields, such as: HI-FI audio; food; medicine; moulds and dies; textile; aerospace and military; watchmaking; pumps and compressors.

The light colour shows the material has not been coated. DLC treatment can be repeated several times, always taking into account the tolerances based on the material treated.