Reducing parasitic losses in internal-combustion engines ranks high on every OEM’s “must-do” agenda, and one of the areas of concentration is piston ring efficiency. Nitriding the rings is an established technology to improve efficiency, but at its Burscheid, Germany, Technology Center, Federal-Mogul has developed a new coating for gasoline engine applications.
The company claims that its CarboGlide coating reduces piston ring friction by up to 20% with a subsequent direct improvement in fuel economy and CO2 emissions.
A possible concern with any coating of reciprocating engine components is degradation of required longevity. Federal-Mogul states that CarboGlide’s high wear resistance will withstand an engine’s full operational life, including high-output gasoline units with turbocharging or direct injection. Because of what is described by the company as its high chemical and physical capability, CarboGlide also protects the cylinder surface from scuffing and scoring, especially under the most critical lubrication conditions.
Said Dr. Marcus Kennedy, Federal-Mogul’s Manager, Physical Coatings: “Ring pack friction is one of the biggest sources of mechanical losses in an engine, and the higher cylinder pressures seen in turbocharged and GDI engines increase that friction as well as increasing the risk of scuffing. CarboGlide-coated rings have been proven in extensive testing to reduce both problems.”
Although developed primarily for car and SUV/light-truck applications, the new technology’s combination of low friction, low wear, and scuffing resistance makes it suitable for other Federal-Mogul products developed for extreme conditions, such as face seals on construction machinery, he added.
The company has released some details of the product. It uses a multilayer amorphous microstructure containing carbon, deposited in diamond-like form, together with hydrogen and tungsten. Kennedy explained that an “advanced process” combining Physical Vapor Deposition and Plasma Enhanced Chemical Vapor Deposition specifically developed for piston-ring application is used to apply the coating, adding that thickness can be up to 10 micron (394 µin), more than three times that of the industry’s latest state-of-the-art DLC (Diamond Like Coating).
The coating’s multilayer architecture, combined with Federal-Mogul’s surface machining and finishing capability, has been designed to ensure the integrity of the coating structure, optimal adhesion, and high coating stability on both steel and cast-iron rings. Tests at the Burscheid Technical Center have included applications involving both cast iron and high-silicon aluminum cylinder bores.
Rainer Jueckstock, Senior Vice President, Federal-Mogul Powertrain Energy, said: “The reduced friction leads to an immediate, cost-effective fuel economy improvement that is easy to implement, helping to reduce the carbon footprint of gasoline-powered vehicles.”
CarboGlide is Federal-Mogul’s third generation of DLC-coated ring technology and is described by the company as its most advanced. It reports that “several” major vehicle manufacturers will launch engines using CarboGlide-coated piston rings during 2011 and 2012.
Federal-Mogul is to exhibit CarboGlide-coated rings plus other technologies designed to improve fuel economy, reduce emissions, and enhance safety, at September’s Frankfurt Auto Show.