LCF and TMF on Ferritic Stainless Steel for Exhaust Application

Due to the more stringent and upcoming laws in terms of environment protection field, the required temperatures in combustion chamber need to be higher in order to reduce particles emissions. This target is reached by engine downsizing (see FIAT and Ford) together with the application of turbochargers, but the new altered conditions lead to a design of exhaust gas manifold that has to take into account an improvement in terms of temperature up to 1050 °C. Above all, materials characterization has to be carried out in order to represent, as close as possible, real operative conditions. Usually, materials for exhaust gas manifold are characterized from HCF, LCF and TMF point of view by testing on cylindrical specimens, but this way it's not possible to detect the effect given by rolling process. In these last years CRF has designed and developed a particular kind of antibuckling in order to allow LCF and TMF characterization on flat specimen at high temperatures with fully reversed strain cycle.This paper will show the results of LCF characterization carried out on flat specimen (th=1.5 [mm]) in strain ratio condition Rɛ=-1 at temperatures of 600[°C] and 800[°C].Furthermore, results of several TMF tests will be showed