Subsurface Microstructural Dynamic Recrystallization In Multiscale Abrasive Wear

This paper evaluates various subsurface microstructures of Hadfield steel worn in different abrasion systems. The abrasion systems are defined according to their abrasion conditions related with the following scales: macro (cone crusher); meso (jaw crusher test) and micro (scratch test) in order to relate the industrial and laboratory conditions. The subsurface microstructures were evaluated by Scanning Electron Microscope, Electron Backscatter Diffraction, X-Ray Diffraction, Focused Ion Beam and Transmission Electron Microscope. The observed wear effects to the surface of the cone crusher mantle are characterized by indentations, grooves, intergranular cracks and grain detachment. The subsurface microstructure of the multiscale abrasive wear conditions was composed of a topmost layer with ultrafine grains, a layer with deformation twins and slip bands. In the cone crusher and the jaw crusher, changes in the shape of the subsurface deformed grains after plastic strain were not observed, leaving deformation twinning as the primary strain mechanism. The cone crusher subsurface microstructure showed dynamic recrystallization characterized by ultrafine-grains, small grains with continuous network carbides in the grain boundary, acicular carbides and annealed twin. The analysis of the ultrafine grains formation considers the energy release at the abrasive/material interface and in the subsurface by deformation as responsible for nucleation and growth of ultrafine grains. The scratch test in {111}//ND grain has the subsurface with ultrafine-grains and deformation twins. The nano-hardness results show that the regions with ultrafinegrains have a higher hardness than the regions with deformed grains, where the plasticity was restored and the hardness of the subsuperficial layer had improved. The models of dynamic recrystallization induced by severe plastic deformation are discussed and correlated to the ultrafine-grains formation.