Tribological behaviour of microalloyed and conventional C–Mn rail steels in a pure sliding condition

This paper compares the tribological behaviour of microalloyed rail steel with conventional C–Mn rail steel under different test conditions (load, temperature and humidity). Pin-on-disc tribological tests were performed inside a climate chamber under different loads (20, 30 and 40 N), relative humidity (15, 55 and 70%) and temperatures (20 and 40 ℃). After the friction and wear tests, the worn surfaces were analysed using both confocal and scanning electron microscopies. The results obtained show that the use of microalloyed steel in railway applications under severe conditions (high loads and humidity) could lead to increased service life of the rails and could extend the time between maintenance operations

Effect of Cyclic Stresses Below the Endurance Limit on the Fatigue Life of 40Cr Steel

The effect of cyclic stresses below the endurance limit on the fatigue life of 40Cr medium-strength carbon steel is studied. Conventional constant-amplitude cyclic tests and specially designed variableamplitude ones are conducted under torsional loading at the stress ratio R = 0.1. The results show that the strengthening effect of cyclic stresses below the endurance limit can be reached if they are applied prior to the exceeding ones. Moreover, the stress amplitude, number of cycles and load sequence are found to be the three major strengthening effect-controlling factors.Изучено влияние циклических напряжений ниже предела выносливости на усталостную долговечность углеродистой стали средней прочности 40Cr. Выполнены стандартные циклические испытания с постоянной амплитудой и специально разработанное испытание с переменной амплитудой при крутящем усилии и коэффициенте асимметрии R = 0,1. Показано, что эффект упрочнения от циклических напряжений ниже предела выносливости достигается при их приложении до напряжений, превышающих этот предел. Установлено, что амплитуда напряжений, число циклов и схема нагружения являются тремя основными факторами, контролирующими эффект упрочнения