Superhard carbon: General Industry Coverage

Lightweighting isn’t the only method available to improve automotive fuel efficiency. Coating engine components, such as cogs, piston rings and piston pins, with hard carbon reduces friction to almost zero, and researchers at the Fraunhofer Institute for Material and Beam Technology IWS have developed the Laser-Arc module (LAM) to apply the coating on a production line.

“Systematic application of our new method could save more than 100 billion liters of fuel each year over the next 10 years,” said Andreas Leson, the institute’s vice director and department head, referencing a study published in the journal Tribology International.

Carbon-based coatings are already applied in volume production, but the institute researchers, led by Leson, Hans-Joachim Scheibe and Volker Weihnacht, have succeeded in producing hydrogen-free, tetrahedral amorphous carbon (ta-C) coatings on an industrial scale at a consistent quality level. At 40 to 70 GPa, these Diamor-trademarked coatings are significantly harder, and therefore more resistant to wear, than conventional diamond-like coatings, according to the institute.

Volker Weihnacht, Andreas Leson and Hans-Joachim Scheibe (left to right) of Fraunhofer IWS developed a Laser-Arc method for depositing diamond-like coatings on components. Image courtesy Dirk Mahler/Fraunhofer.

“Unfortunately, you can’t just scrape off diamond dust and press it onto a component, so we had to look for a different method,” Scheibe said.

Similar to a film projector, LAM generates an arc between an anode and a cathode (the carbon) in a vacuum, the researchers explained. The arc is initiated by a laser pulse on the carbon target. This produces a plasma that consists of carbon ions, and the plasma is deposited as a coating on the workpiece in a vacuum.