Breakthrough in Piston Ring Coating Technology

A breakthrough piston ring coating called DuroGlide® from Federal-Mogul Corporation’s Powertrain Division has set new standards for durability and friction reduction.

The benefits are applicable to petrol engines and both light and heavy-duty diesel engine applications. With DuroGlide, the company has developed advanced material and manufacturing processes to create the industry’s highest performing piston rings, capable of making new advances in vehicle manufacturers’ demands for fuel efficiency and CO2 reduction.

“DuroGlide is not an evolution; it’s a breakthrough,” said Gian Maria Olivetti, vice president and chief technology officer, Federal-Mogul Powertrain. “Its performance exceeds even our premium existing products, providing the ultimate combination of low friction with exceptional durability, even in the most critical engine environments.”

In testing, DuroGlide-coated piston rings have shown the highest durability of any piston ring coating type and contribute fuel economy savings up to 1.5 percent, equivalent to a CO2 reduction of up to 3 g/km for a light vehicle, depending upon the engine application. In addition to the efficiency improvement from reduced friction, DuroGlide also provided superior scuff resistance. This makes the technology particularly suitable for higher performing and fuel-efficient engines where adverse lubrication conditions are generated by smoother cylinder bore surfaces, low viscosity oils, aggressive combustion strategies and very high temperatures.

DuroGlide’s advanced material innovation is based on an amorphous high-hardness carbon-based coating, which improves lubricity between surfaces by providing a physically and chemically inert barrier, thus preventing boundary lubrication contact. It contains diamond-structured carbon in a higher concentration than has been previously achieved (around 50 percent), giving exceptional hardness and wear resistance. Wear rates as low as half that of the best existing piston ring coatings have been obtained.

“Until now, the high durability carbon-based coatings available on the market have usually been restricted to a maximum of a few microns thickness because greater thicknesses increase residual stresses, leading to a higher risk of delamination,” explained Dr. Marcus Kennedy, manager, physical coatings, Rings & Liners, Federal-Mogul Powertrain.

“Additionally, good friction and wear performance requires very smooth coating surfaces which cannot be achieved with conventional surface finishing processes.”

Federal-Mogul has developed an innovative surface treatment and physical vapor deposition manufacturing process which results in a coating thickness of over 20 microns without the risk of delamination. These process innovations enable use of the specialized coating on components with high contact pressure like piston rings. The company has also implemented a special polishing process which provides an extremely smooth surface finish.

DuroGlide can be used throughout the ring pack on all known piston ring materials made of cast iron or steel. Developed in Burscheid, Germany, where production will commence during 2014, DuroGlide will be introduced in several engine projects for gasoline and diesel engine applications.

“By combining cutting-edge materials research with advanced manufacturing techniques, we maintain our position of technical leadership,” said Olivetti. “DuroGlide piston rings will help our customers achieve significant progress in reducing fuel consumption and CO2 emissions, while extending engine durability and reliability.”