The structural-phase state changes under the pulse current influence on the fatigue loaded steel

Structure and phase transformations in Fe-0.6C-1Mn-2Si steel subjected to multicyclic fatigue tests under normal conditions and with intermediate electrostimulation are investigated by the methods of metallography of etched microsections and scanning and transmission electron diffraction microscopy of thin foils and carbon replica. It is demonstrated that fatigue failure under normal loading is preceded by complete dissolution of initial cementite particles with carbon localized on structural defects (dislocations, subboundaries, and boundaries), micropores, and microcracks. Electrostimulation, promoting the relaxation of stress concentrators through dissolution of particles localized on the grain boundaries and the state change of the interphase boundaries between the matrix and second-phase particle, causes the mean and maximum subcritical crack length to increase together with the thickness of the sample layer involved in the strain of the material and the zone of fatigue crack growth. This is accompanied by a significant increase in the operating lifetime of the material.