Engineering Material Selection for Automotive Exhaust Systems Using CES Software

Abstract

The aim of this report is focused onreviewing the automotive exhaust system with respect to its in-service conditionsand selection of suitablematerials for exhaust manifold, downpipe silencer/ muffler box and tail pipe in an exhaust system. In doing this, the functions of each component were discussed, highlighting how they function as part of a system and CES Edupack software was employed in the material selection process. Mass, cost, high temperature (>800oC for exhaust manifold and >400oC for downpipe silencer/ muffler box and tail pipe) and high corrosion resistance were used as criteria for the material selection. Variety of materials including Nickel-based superalloys, stainless steel, Nickel-chromium alloys were obtained in the search result for exhaust manifold. Similarly, low alloy steels, stainless steel, grey cast iron,Nickel-based superalloys, Nickel-chromium alloys were obtained in the search result for downpipe silencer/ muffler box and tail pipe. Nickel-based superalloys and Nickel-chromium alloys possess suitable properties for this application, but were not selected due to their high densities and high cost. Low allow steels were not selected because they tends to exhibits poor corrosion resistance when exposed to salt on the road surface and condensate from the exhaust system. Grey cast iron has low tensile strength and elongation and therefore not exhibit enough toughness required to withstand the severe working conditions.However, stainless steel (Ferritic stainless steel and Austenitic stainless steel) was selected due to its considerable price, low density, excellent corrosion resistant and acceptable strength at elevated temperatures.