Lasers Get High Thickness at High Speed

MONDAY, JUNE 15, 2015

DRESDEN, GERMANY--Fuel savings of 100 billion liters a year are the promise of a new laser-assisted carbon coating application method now in development.

The laser arc method allows "layers of carbon almost as hard as diamond" to "be applied on an industrial scale at high coating rates and with high thicknesses," according to a research announcement from Fraunhofer Institute for Material and Beam Technology IWS, part of the Fraunhofer-Gesellschaft R&D organization.

The advance comes in the area of diamond-like carbon (DLC) coating of engine components such as pins and piston rings. Scientists know how to apply these coatings, which can friction in engines to near zero.

Until now, however, no process has allowed for high coating rates of high thicknesses on an industrial scale with consistent quality.

The answer, the team says, is part process and part product.

Diamond Dust

The team has produced hydrogen-free ta-C coatings that are applied with a pulsed later.

Tetrahedral amorphous carbon (ta-C) is the hardest, strongest and slickest type of DLC coating. Essentially bonded carbon atoms, two micrometers of thickness can add years or even decades of abrasion resistance.

But applying a plasma of carbon ions isn't easy.

“Unfortunately, you can’t just scrape off diamond dust and press it onto the component," said Fraunhofer's Dr. Hans-Joachim Schiebe, who has spent over 30 years investigating carbon’s friction-reducing properties.

"So we had to look for a different method."

Cue the lasers.

Powering Projectors

The team compares its 21st-century laser method to an "old-fashioned film projector."

Fraunhofer Fraunhofer
Images unless indicated:

Fraunhofer's new process can deposit a pure carbon coating onto components, reducing friction to near zero.

The institute explains:

"...[T]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 result is a method that can be used to deposit ta-C coatings of up to 20 micrometers thick at high coating rates, the team says.

Cutting Friction

By quickly, thickly coating engine components to slick diamond hardness, the potential for fuel savings is enormous, the team says.

AndreasLeson AndreasLeson

Motorcyclist and scientist, Professor Andreas Leson believes his new coating and method can reduce the environmental impact of his off-hours passion.

“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,” says the team's Dr. Volker Weihnacht.

Reducing engine friction will also help Europeans meet the tightening emissions targets expected from the European Union, the team says.

The research has drawn the buy-in of BMW, which is "working intensively on the industrial-scale implementation of ta-C engine components in its various vehicle models," Fraunhofer reports.

The technology also received the 2015 Joseph von Fraunhofer Prize.

Biker Boost

For Dr. Andreas Leson, the research has been a labor of love. Outside the lab, Leson is a serious motorcycle aficionado.

 “The fact that our research is helping to make motorcycling more environmentally friendly eases my conscience every time I go for a ride," he says.


Tagged categories: Automotive coatings; Coating Application; EMEA (Europe, Middle East and Africa); Energy efficiency; OEM (Original Equipment Manufacturers); Protective Coatings; Research

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