HYDROGEN EMBRITTLEMENT OF THE LOW-CARBON STEEL PRODUCED BY ELECTRON BEAM ADDITIVE MANUFACTURING

The effect of cathodic hydrogen charging of the Fe-(1.8-2.1)Mn-(0.7-1.0)Si-(0.05-0.11)C low-carbon steel, produced by electron-beam additive manufacturing and industrial casting, on its mechanical properties and fracture mechanisms is studied in different electrolytic solutions. Hydrogen charging causes an increase in the yield strength and a decrease in the elongation both for the steel manufactured by the additive method (ferritic steel) and for the normalized steel produced by the industrial method (ferritic-pearlitic steel). An increased duration of hydrogen charging from 5 to 20 hours at a current density of j(H) = 250 mA/cm(2) (NaCl+NH4SCN aqueous solution) is accompanied by an increase of the hydrogen embrittlement index for the additively produced specimens (I-H(5h) = 13%, I-H(20h) = 19%), but does not affect the I-H-value for the normalized industrial steel (I-H(5h) = 28%, I-H(20h) = 30%). Even at a lower current density and a shorter charging duration, the use of an aqueous solution of sulfuric acid (H2SO4+CH4N2S) causes stronger hydrogen-induced effects than the charging in an aqueous solution of sodium chloride. Regardless of the manufacturing method and charging regime, hydrogen charging contributes to the formation of fish-eye defects on the fracture surfaces of steels. It is found out that under similar hydrogen charging regimes, the deteriorative effect of hydrogen is less pronounced in the steel produced by the additive manufacture.