Characterization and Ranking of Materials for Exhaust Systems Under Thermal-Cycling Condition 2013-01-0512

There is a broad range of material choices for on-road and off-road exhaust systems. The final selection of the materials depends on the balance of engineering performance of the materials and the cost. Thermal-cycling resistance of exhaust materials is an extremely important criterion for the long-term durability and reliability performance of very high temperature exhaust components and systems. To optimize the thermal-cycling resistance and cost of those materials, a selection matrix must be established. Several material evaluation and selection matrices are already available, however, these are not sufficient to meet the industry needs. The current procedure of material selection is essentially based on the trial-and-error approach, which is not efficient in the current market environment.

In this paper, a general rational approach for thermal-cycling resistance characterization and ranking is demonstrated. Subsequently, the effectiveness of the V-shape specimen testing in evaluating thermal-cycling resistance performance for various stainless steels is demonstrated. Finally, a simple parameter λ = kσ_f / Eα, which combines the material strength, thermal conductivity, and thermal expansion, is found to be the new breakthrough parameter, correlating to V-shape thermal-cycling test results. Results on four currently used stainless steels verify the correlations and indicate the validity of this approach.