Surface modification on AISI 316L stainless steels by nanosecond laser with boron nitride powders

Abstract

Austenitic stainless steels AISI 316L is widely used in chemical and food manufacturing because they possess a unique combination of mechanical and corrosion resistance properties. However, applications of 316L stainless steels are limited due to their relatively low yield strength and low hardness (200 HV). Austenitic stainless steels can not be transformation hardened by heat treatment. Therefore, this work investigates the effect of nanosecond laser surface treatment on 316L stainless steel with boron nitride (BN) powder coating to improve its hardness and wear properties. The boron nitride power was used to improve its wear resistance by lower surface friction. The laser heating effect can be controlled by adjusting the laser power and scanning speed. We measured the laser treated layer thickness and the hardness along its cross-section by a micro Vickers hardness machine. The results showed that the laser process hardened the top surface to 290 HV hardness up to 250 μm depth. The structure of the laser treated region was strongly affected by the laser scanning parameters and create smaller grain size long the laser track lines. The BN powders did not have significant effect on hardness. The laser treated region had material redeposit on the surface, leading to rougher surface and higher corrosion rate measured by a potentiodynamic test.