The dominant strategy in the vehicle industry is to generate more power from smaller engines using turbocharging or other technologies that create extremely high exhaust gas temperatures. On some applications, we are fast approaching a point where today’s multi-layer stainless steel (MLS) gaskets are being taken to the performance limits of their thermal and mechanical properties. New sealing systems are required.

—Gérard Chochoy, senior vice president, Powertrain Sealing and Bearings

Turbocharging and exhaust gas recirculation (EGR) also present additional challenges by introducing more joint faces into the exhaust system. At these points, movement of the mating surfaces and flange distortion over the lifetime of the vehicle can be significant. With more joint faces and temperature gradients, a conventional static gasket is ineffective, Chochoy added.

Federal-Mogul has addressed these challenges through its development of a family of HTA gasket materials. Even at higher temperatures, the microhardness, creep resistance and dynamic sealing of the HTA materials are superior to the industry standard “301 full hard” stainless steel, which loses mechanical strength beyond 427 °C 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.

Solving the challenge of developing suitable high temperature materials was ultimately only part of the story. The micro-sealing performance of an exhaust gasket is essential to ensure environmental and emissions regulations, accurate engine management data and correct the performance of adjacent engine components and systems. A leaking gasket, for example, can introduce air into the exhaust system, causing the engine management system to switch to a richer fuel charge, thereby reducing engine efficiency and fuel economy while increasing emissions. Federal-Mogul also has developed a unique High Temperature Coating (HTC) that can be applied to the gasket surface to seal the mating flanges and to reduce the effects of motion between them.

—Gérard Chochoy

HTC is an environmentally-friendly, water-based product that eliminates the need for materials containing molybdenum disulphide. It contains a carefully designed triple binder system that provides both superior sealing performance and consistent friction properties over a wide temperature range. HTC demonstrates thermal stability to over 1000°C, while conventional molybdenum-based coatings are reduced to ash at such temperatures, said Jim Zwick, global director of product technology, gaskets and heat shields.