CORROSION OF ULTRA-FINE GRAINED STEEL PRODUCED BY SEVERE PLASTIC DEFORMATION

Abstract

Ultra Fine Grained (UFG) steels were processed by using multi-axial forging, a technique of severe plastic deformation. Mild steel, 1024 steel, and HSLA steel specimens were processed using six passes of multi-axial forging. Optical microscopy revealed grain refinement in all the steels studied. No reported work exists in literature that attempts to investigate the electrochemical properties of the multi-axially forged material, especially steel, with its changed microstructure. Present work investigated the corrosion behavior of various severely deformed ultra fine-grained steels. Immersion tests, potentiodynamic tests, and salt spray tests were performed in chloride environments. By and large, ultra-fine grained steels showed improved corrosion behavior compared to their coarse-grained counterparts. Ultra-fine grained HSLA steels showed relatively inferior corrosion performance compared to UFG plain carbon steels, especially in dilute solutions. The improvement in corrosion properties is explained on the basis of microstructural evolution with respect to grain size, dislocation population, and substructure development.