Applying carbon coatings to engine components, such as piston rings and pins, reduces friction and lowers fuel consumption. Using a new laser-based method, researchers at Fraunhofer-Gesellschaft, Munich, Germany, say they can now produce layers of carbon that are almost as hard as diamond. The team of researchers have created hydrogen-free tetrahedral amorphous carbon coatings of up to 20 micrometers, which, they say, are more resistant to wear than conventional diamond-like coatings.
To achieve the industrial-level coating process, the laser generates an arc between an anode and a cathode (the carbon) in a vacuum. The arc, initiated by a laser pulse on the carbon target, produces a plasma consisting of carbon ions, which is deposited as a coating on the workpiece in the vacuum. To run the process on an industrial scale, a pulsed laser is vertically scanned across a rotating graphite cylinder as a means of controlling the arc. Due to the scanning motion and rotation, the cylinder is converted evenly into plasma. To ensure a consistently smooth coating, a magnetic field guides the plasma and filters out dirt particles.
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.
