International. Researchers in Fraunhofer (Germany) have developed a laser arc method with which carbon layers almost as hard as diamond can be applied on an industrial scale at high coating rates and with high thicknesses.
By applying carbon coatings to engine components, such as rings and piston pins, fuel consumption can be reduced. "Systematic application of our new method could save more than 100 million liters of fuel each year for the next ten years," said Prof. Andreas Leson of the Fraunhofer Institute, referencing a study that was published in the journal Tribology International in 2012.
Carbon-based coatings are already used in volume production. But now the Institute's team of researchers has succeeded in producing ta-C-free hydrogen coatings on an industrial scale at a consistent level of quality.
These tetrahedral amorphous carbon coatings are significantly harder and therefore more wear-resistant than conventional diamond-type coatings. "Unfortunately, you can't just scrape diamond powder and press on the component. So we had to look for a different method," said Dr. Scheibe, who has spent more than 30 years researching properties that reduce carbon friction.
In a style similar to that of old 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 target carbon. This produces a plasma consisting of carbon ions, which is deposited as a coating on the workpiece in a vacuum. To run this process on an industrial scale, a pulse laser is scanned vertically through a graphite cylinder that rotates as a means to control the arc. The cylinder is converted into plasma evenly thanks to the rotation and movement of exploration. To ensure a smooth coating consistently, a magnetic field guides the plasma and filters out dirt particles.
