Diamond-like carbon coating for engines could save '100 billion litres of fuel' annually

Scientists have developed 'laser arc' method to apply coating on industrial scale

A new laser method to apply an incredibly hard carbon coating to engine components on the production line could save billions of litres of fuel worldwide every year, says researchers.

Scientists have previously known that coating engine components such as piston rings and pins, with diamond-like carbon minimises friction to almost zero and reduces fuel consumption. As such carbon-based coatings are already used in volume production.

However, a team of researchers at the Fraunhofer Institute in Dresden, led by Professor Andreas Leson, Dr. Hans-Joachim Scheibe and Dr. Volker Weihnacht, have now developed a laser arc method that can add layers of significantly harder, hydrogen-free carbon, called tetrahedral amorphous carbon (ta-C), to engine components than is usually used on an industrial scale.

Leson said: “Systematic application of our new method could save more than 100 billion litres of fuel each year over the next ten years.”

In a similar style to old-fashioned film projectors, the laser arc method generates an arc between an anode and a cathode (the carbon) in a vacuum. The arc is initiated by a laser pulse on the carbon target. This produces a plasma consisting of carbon ions, which is deposited as a coating on the workpiece in the vacuum. To run this process on an industrial scale, a pulsed laser is vertically scanned across a rotating graphite cylinder as a means of controlling the arc. The cylinder is converted evenly into plasma thanks to the scanning motion and rotation. To ensure a consistently smooth coating, a magnetic field guides the plasma and filters out any particles of dirt.

The laser arc method can be used to deposit very thick ta-C coatings of up to 20 micrometers at high coating rates. Weihnacht said: “High coating thicknesses are crucial for certain applications – especially in the auto industry, where components are exposed to enormous loads over long periods of time.”

The automotive and motorcycle manufacturer BMW is working intensively on the industrial-scale implementation of ta-C engine components in its various vehicle models with the aim of reducing their fuel consumption.

Andreas Leson, Hans-Joachim Scheibe and Volker Weihnacht received the 2015 Joseph von Fraunhofer Prize for the development of the laser arc method and the application of ta-C coatings in volume production.