The term “hotted up engine” has taken on a wholly new meaning in the world of power unit downsizing. Getting smaller engines to produce as much power and torque as their larger predecessors is pushing up the temperatures of critical components. In some applications, exhaust heat increases from 400°C (752°F) to beyond 1000°C (1832°F), according to Federal-Mogul, which is seeing growing demand for its high-temperature gasket technology from European automakers engaged in engine downsizing strategies.
Sealing systems for turbochargers, exhaust manifolds, and exhaust gas recirculation (EGR) assemblies all have to meet these needs. To do so, Federal-Mogul has developed a family of high-temperature gasket materials called High Temperature Alloy (HTA) with complementary High Temperature Coatings (HTCs) that help to ensure reliable long-term sealing.
Already proven in the heavy-duty diesel sector, Federal-Mogul reports that light-duty diesel and gasoline engine applications are already in progress with production now under way in Germany.
Gérard Chochoy, the company’s Senior Vice President, Powertrain Sealing and Bearings, said: “On some applications, we are fast approaching a point where today’s multilayer stainless steel (MLS) gaskets are being taken to the limits of their thermal and mechanical performance. New sealing systems are required and Federal-Mogul has with its new HTA gaskets and HTC coating an affordable, innovative, proven technical solution.”
He explained that Federal-Mogul had developed the gasket systems to operate reliably in highly demanding powertrain applications with fluctuating high temperatures and dynamic mechanical loads. The strengthening trend toward the use of turbocharged engines with higher exhaust system temperatures brought thermal-management issues and, consequently, products capable of high-temperature sealing were becoming more important.
Turbocharging and EGR present additional challenges by introducing more joint faces into the exhaust system, explained Chochoy. At these points, movement of the mating surfaces and flange distortion over the lifetime of the vehicle could be significant: “With more joint faces and temperature gradients, a conventional static gasket is ineffective.”
Even at higher temperatures, the micro-hardness, creep resistance, and dynamic sealing of the HTA materials are described as being superior to the industry standard “301 full hard” stainless steel, which loses mechanical strength beyond 427°C (800°F) and can crack or otherwise experience a loss of sealing ability.
HTA gaskets are available with specifications matched to the individual thermal and mechanical requirements of a wide range of demanding applications, including turbochargers, downpipes, exhaust manifolds, and EGR.
Also new from Federal-Mogul is a pliable coating to provide required exhaust gas micro-sealing. The coating required the achievement of very low friction to prevent galling and wear of highly mobile joints.
“The micro-sealing performance of an exhaust gasket is essential to ensure environmental and emissions performance and to achieve accurate engine management data,” said Chochoy. “The HTC coating can be applied to the gasket surface to seal the mating flanges and to reduce the effects of motion between them.”
The water-based coating eliminates the need for materials containing molybdenum disulfide. It contains a triple-binder system that has been designed to provide both superior sealing performance and consistent friction properties over a wide temperature range.
Jim Zwick, Federal-Mogul’s Global Director Product Technology, Gaskets and Heatshields, added: “HTC is thermally stable at temperatures of more than 1000°C; conventional molybdenum-based coatings are reduced to ash at such temperatures.”