Surface nanocrystallization of low -alloyed steel by multidirectional severe plastic deformation for improved mechanical and tribological properties

Abstract

Surface nanocrystallization of the low -alloyed structural 40X steel by severe plastic deformation (SPD) was realized due to mechanical -pulse treatment (MPT) with different modes: unidirectional and multidirectional. The strengthened layer s with nanocrystalline structure (NCS) formed in the steel by both mode of deformation were characterized by improved mechanical properties and wear resistance compared with the heat -treated steel. Moreover, multidirectional deformation during MPT resulted in lower grain size of the surface layer, its highe r microhardness and the depth of the strengthening, and favourable surface parameters providing highe r wear resistance compared with that produced with unidirectional deformation.