Component strength key goal at Federal-Mogul

  • 05-Feb-2011 03:36 EST

"No design can be static in our industry," said Federal-Mogul's Keri Westbrooke. The Magnum Monosteel piston's reduced-friction architecture translates to improved fuel economy and mass reduction.

Federal-Mogul's latest evolution of pistons, cylinder liners, and bearings are stronger and more durable than ever, making the new designs capable of handling the increased cylinder pressures and thermal loads produced by highly boosted heavy-duty diesel engines.

Development testing is ongoing with global commercial vehicle makers as well as engine manufacturers in North America and Europe for Federal-Mogul's Magnum Monosteel piston, a next-generation version of the company's Monosteel piston that production-debuted on the Caterpillar C7 diesel engine in 2003.

Both the original Monosteel and the forthcoming Magnum Monosteel—intended primarily for the heavy-duty truck market—employ patented dual friction-welded construction.

"But the Magnum has an 'aperture' in the skirt to reduce skirt drag and reciprocating mass," explained Keri Westbrooke, Director of Engineering and Technology for Federal-Mogul Corp.'s Powertrain Energy group in Plymouth, MI.

Even though the Magnum's unique "double-band" steel piston skirt helps reduce the overall skirt area by 40%, the smaller skirt does not adversely affect piston guidance or stability.

"The Magnum skirt contacts the cylinder bore on both the upper and lower bands simultaneously. We achieve exactly the same guidance properties as a full-length skirt and an improved protective oil film on the upper skirt band," said Westbrooke.

Both the Magnum and a smaller-bore Light Duty Vehicle (LDV) Monosteel will reach the market in the 2014/2015 time frame.

"The small-diameter LDV Monosteel piston has the same architecture—closed, welded cooling gallery—but the LDV Monosteel may use thinner wall castings which are more mass efficient than forgings. We also may use the patented Federal-Mogul induction welding process that preheats the mating surfaces by induction coils prior to welding. This process enables lower welding forces and the thinner piston sections," explained Westbrooke.

Federal-Mogul is production-process ready with a specially coated piston.

The electroplated chrome-based coated piston—with hard particles encapsulated in the chrome substrate—is flush with benefits, including thermal protection for the crown as well as corrosion protection for the piston's exposure to the acids formed in an EGR (exhaust gas recirculation) system.

"This technology will also reduce the carbon formation on the piston's top land, and it will increase the bearing load capability on the pin bore," said Westbrooke.

A soon-to-market solution from Federal-Mogul will shield cylinder liners from possible long-term cavitation caused by a piston's side force impacts.

"The metallic plasma spray process is a well-developed technology within Federal-Mogul that has been used for decades as a wear-resistant peripheral coating for top compression rings. But by using this technology as a protective coating on cylinder liners, Federal-Mogul is able to provide customers with a component that will last for the scheduled life of the engine," Westbrooke said.

A chemical treatment for engine bearings is being readied for production release later in 2011.

IROX-coated engine bearings will have a polyamideimide polymer resin overlay that includes hard particles and solid lubricants suspended in the coating. An initial targeted use for IROX-coated bearings is stop-start engine applications.

"As cylinder pressures in commercial vehicle engines continue to increase—putting higher and higher loads on the engine bearings—the IROX overlay will provide a longer life and higher fatigue strength than conventional leaded electroplates," said Bob Sturk, Chief Applications Engineer for Bearings–North America at Federal-Mogul's technical center in Plymouth, MI.

Although there are no current regulations restricting lead usage on heavy-duty engines, the absence of lead in IROX means the coating is environmentally compatible, according to Sturk.

In developing IROX as a coating for engine bearings, technical experts knew the material would need to withstand cyclic loading without compromising the "sliding properties" for movement within a thin oil film. "Our scientists borrowed technology from our highly successful GLYCODUR product line and built upon that," Sturk said.

The IROX material will undergo durability tests in a 15-L Class 8 truck engine as well as durability tests on a midrange diesel engine.

"Because of its ability to offer good frictional performance under low oil conditions, the IROX coating could find other uses on internal engine components, such as piston skirts, camshaft bearings, and thrust washers," explained Sturk.

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