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One way to respect the Euro 5 depollution norm is the downsizing of the engine, which leads to more severe in-use operating conditions especially an increase of the exhaust gas temperature. Consequently, the hot part of the exhaust system, i.e., from manifold to the catalytic converter, could be subjected to maximal temperature up to 1000°C. Moreover, an improved durability and longer life guaranties are also required for such parts. In this context, a new ferritic stainless steel grade has been developed, named K44X (AISI 444, EN 1.4521), which fulfills these new specifications and that could be applied for both fabricated manifold and turbocharger shells. The K44X, with a chromium content of 19% (weight), an addition of 2% molybdenum and 0.6% of niobium, offers excellent high temperature properties like cyclic oxidation, creep and thermal fatigue resistance, a low thermal expansion coefficient.

Due to the evolution of emission control standards, new pollution control systems will be necessarily used for off-road vehicles and trucks exhaust systems and in the near future for passenger cars. Indeed, the will to reduce NOx emission through Euro 5 (2009) and then to Euro 6 (2014) and American EPA Tier 4 (2008-2015) imposes the implementation of a new after-treatment system within the exhaust line. One of the most promising technologies takes advantage of the reduction feature of ammonia (NH₃) on NOx. This system called Selective Catalytic Reduction (SCR) couldn't be developed by storing directly ammonia as a reduction agent on the vehicle due to its high toxicity and flammability. It is why urea is used as an ammonia generator through thermolysis reaction.