Investigation of tribological behavior of coated and untreated rail steels under wet conditions

Abstract

Rails are exposed to more stresses, especially in the regions of narrow radius curves and switch passages. Therefore, the tribological features of these regions are important. In this study, the effect of boronization on tribological properties was examined. For this purpose, experiments were carried out on samples boronized at 800 degrees C for 2 h and 8 h and on untreated samples. With these experiments, the friction coefficient, volume loss and surface roughness values of the samples under wet conditions were examined. In addition, the microstructures of the material after boriding were observed by SEM and EDX. The variance and regression method (ANOVA) was used for the statistical analysis of the experimental results. After SEM examinations, a coating layer of similar to 22 mu m (FeB) and similar to 48 mu m (FeB+Fe2B) were obtained on the surface of the rail steels boronized for 2 and 8 h, respectively. The microhardness of the rail steels, which was similar to 300 HV for the untreated sample, increased to similar to 1900 HV and similar to 2400 HV with the boronizing process boronized for 2 and 8 h, respectively. According to the ANOVA results, the effects of the boronizing process on the decrease of the friction coefficient and the volume loss were calculated as 42% and 46%, respectively. Finally, according to the corrosion results, the corrosion resistance of the boronized rail steels decreased with the boride layer formed.