Effect Of C,Si And Cr Contents On Hydrogen Permeation Characteristics Of Heavy Haul Wheel Steel

On the basis of the review of the researches and developments for wheel steel andhydrogen diffusion and penetration characteristics in metals, the effect of carbon,silicon and chromium contents on hydrogen permeation characteristics and the criticalhydrogen mass fraction of the hydrogen blistering of heavy haul wheel steels havebeen studied. Firstly, the microstructures of the investigated steels were analyzed bymeans of metallographic microscopy, X-ray diffraction (XRD) measurement,scanning electron microscopy (SEM) and transmission electron microscopy (TEM).Then the hydrogen permeation characteristics and the hydrogen blisteringphenomenon were studied by the electrochemical method. These results can provide aguidance to the researches and developments of high-performance heavy haul wheelsteels.It was found that the microstructures of the steels are the mixed is ferrite+pearliteafter the heat treatment, and the pearlite lamellar spacing in the range of270-350nm.The pearlite content increased and the pearlite lamella spacing decreased with theincrease of the content of C, Si and Cr. Steel4#has a pearlite content of95.7wt%which is the maximum value among four steels, and the pearlite lamella spacing isabout270nm which is the minimum value compared with the others. Because thechemical composition has an effect on pearlite content and pearlite lamella spacing,the diffusion coefficient of hydrogen in the steels and the critical hydrogen massfraction of the hydrogen blistering.By hydrogen permeation experiments,it was found that,by C,Si and Cr contents canbe greatly influenced the diffusion coefficient of hydrogen in steel decreased asincreasing the contents of C, Si and Cr. Steel4#has a maximum hydrogen diffusioncoefficient,1.963×10-6cm2/s,at20℃among four steels. During the experiments ofhydrogen blistering, it was found that the charging current density and the criticalhydrogen concentration of hydrogen blistering increased as increasing the contents ofC, Si and Cr. As the maximum the charging current density and the critical hydrogen concentration of hydrogen blistering for steel4#are6mA/cm2and3.638wppm,respectively.Such a result is related to the number of irreversible hydrogentraps corresponding to the amount of pearlite and the pearlite lamella spacing.