Formation of Surface Nano/Ultrafine Structure using Deep Rolling Process on the AISI 316L Stainless Steel

Abstract

In the present work, effect of deep cold rolling process known as deep rolling on near–surface microstructure and hardness of an austenitic stainless steel has been evaluated. Deep rolling process using a ball–point device was carried out on the bar–shaped AISI 316L stainless steel specimens. The process was performed at 15 and 26 passes with 0.2mm/s longitudinal rate and 22.4rpm bar rotation. Microstructure and hardness were investigated by feritscope, X–ray diffract meter, field emission scanning electron microscope and Vickers¬ micro–indenter at 0.1kgf. A composite microstructure, consisting of ultrafine and nano grains (200nm and 70nm), mechanical twins and strain–induced marten site, was observed in the near–surface regions. Surface hardness was increased from 210 to 450 and 500HV0.1 after 15 and 26 passes, respectively