Fatigue properties of austenitic Mn-steel in explosion depth hardened condition

Abstract: Railway rails, including crossings and turnouts, are exposed to high impact loads during use and have to resist large cyclic stresses. An extended life time of the railway rails is desired. The high cyclic loads could cause material fracture and a catastrophic failure can occur.The material studied in this master thesis is cast austenitic manganese steel - Mn13, Explosion Depth Hardened - EDH. Due to the high wear resistance and hardening during use the material can be applied in railway components. The project was cooperation between Chalmers University of Technology and the Austrian company VAE GmbH. The Mn13 EDH steel investigated was the third material in the MU16 CHARMEC-project. The specimens were provided by VAE GmbH.Tensile, fatigue and hardness tests were performed to examine the mechanical properties and the microstructure of the Mn13-steel was characterised using optical microscopy. Tensile testing was done at three different temperatures (+20°C, +100°C and -60°C) and with two different strain rates (10-4s-1 and 10-1s-1) to determine the effects of deformation speed and temperature. The higher strain rate mainly showed a larger resistance to plastic deformation until failure. The different temperatures had a small influence on the final mechanical properties. Low cycle fatigue testing – LCF was used for performing cyclic uniaxial push-pull tests. The fatigue testing was controlled either by constant strain or stress amplitudes at room temperature. The strain controlled amplitudes were 0.3, 0.4, 0.6 and 1% and the larger amplitudes resulted in the largest plastic strains. Due to small defects in the material, the number of cycles to failure in fatigue testing scattered.