Federal-Mogul Powertrain, a division of Federal-Mogul Holdings Corporation, is applying its expertise in light vehicle engine bearings to provide robust, lead-free bearing solutions to the heavy-duty market. The company's product offering, in which the upper and lower halves of a bearing shell pair are individually optimized, has pioneered the introduction of lead-free bearing materials that offer increased load capacity and wear resistance for these heavy-duty engines.
For today's bearings, factors such as seizure, adaptability and wear resistance have become as important as load carrying capacity. "By selecting a material with high fatigue resistance for the bearing shell that carries the higher loads, and a material for the counter shell with good embeddability and highly tolerant of particles present in the engine oil, we are able to offer a robust solution," says Gian Maria Olivetti, Chief Technology Officer, Federal-Mogul Powertrain.
The difference in bearing load arises because heavy combustion loads occur only on the upper half of the connected rod and the lower half of a main bearing. Federal-Mogul's solution provides a coated bearing for the high-loaded side combined with an aluminium substrate for the counter (less loaded) shell. Bearing coatings consist of a sputter, polymer or electroplate overlay, which improves engine robustness.
While there is no legislation in place that limits lead in bearings for the heavy-duty sector, Federal-Mogul's extensive experience in lead-free bearings for the light vehicle sector can be easily adapted to satisfy any future proposed legislation for heavy-duty engines. In addition to environmental benefits, lead-free materials also provide improved bearing fatigue life. "Our lead-free bearings use a superior substrate made either from cast or sintered material. A robust solution for rod bearing loads up to 95 MPa previously necessitated the use of a sputtered coating, but with lead-free materials we can tailor our requirements to fit the specific needs of the engine, such as using our IROX polymer coating," explains Joachim Häring, Manager, Application Engineering, Bearings, Europe, Federal-Mogul Powertrain. "There is a clear market trend for high strength aluminium to replace electroplated bearing materials for the lower main bearing. IROX can be used as an upgrade to the high strength aluminium, optimizing the load capacity and the wear resistance, if needed," he adds.
Achieving excellent bearing performance required Federal-Mogul to utilize state-of-the-art testing such as EDX (energy dispersive x-ray) spectroscopy and SEM (scanning electron microscopy). Additionally, EHD (elastohydrodynamic) studies or FEM (Finite Element Methods) were used to optimize the bearing and its environment. Along with the development of lead-free bearing materials, necessary new manufacturing processes and test procedures, such as wear and embeddability tests, were also introduced.
Federal-Mogul's first heavy-duty application of lead-free bearings is in series production with one global OEM and being considered by other customers. Heavy-duty engines contain a much higher number of bearing parts compared to passenger car engines, extending beyond the crank train to rocker gear, cam drives and cam bushings. As a result, customers benefit from working with a single supplier such as Federal-Mogul which has a comprehensive system understanding and full bearing material portfolio. "Our extensive experience with lead-free materials in the automotive sector is invaluable," says Häring. "We have been able to efficiently adapt to the heavy-duty market where vehicle lifetime mileages are much higher, reaching up to 1.5 million kilometers."
Future trends for heavy-duty engines include higher combustion loads (with peak pressures reaching 250 bar or more); greater use of stop-start and hybrid operation; and thinner oils to improve efficiency and increased wear resistance for longer engine life. Federal-Mogul is well-positioned to meet these future challenges, with developments underway that indicate how current materials can be adapted to satisfy the needs of future engine requirements.
Lead-free bearing materials are developed at Federal-Mogul's Wiesbaden technology center in Germany. The facility has nearly 120 years of experience in bearing design and development. As part of Federal-Mogul's commitment to providing regional support to its global customer base, the company recently announced its acquisition of Russian bearing manufacturer DZV, which provides an excellent growth platform for increased presence in the commercial vehicle and industrial engine market in Eastern Europe.
Federal-Mogul presented its range of bearings at the IAA Commercial Vehicles Show in Hannover from September 23 to October 2, 2014, hall 13, stand C28.