Microstructure Evolution and Mechanical Properties of AISI 430 Ferritic Stainless Steel Strengthened Through Laser Carburization

Abstract

Carburization assisted by laser processing is a promising method to strengthen metallic materials. Direct laser beam carburization is implemented for the first time on thin AISI 430 ferritic stainless steel (FSS) sheets with graphite coating under different conditions. Microstructural morphology, phase constitution, carbon content, microhardness, and tensile behavior are investigated to evaluate the laser carburization effect. The carburized zone presents different morphologies according to the linear energy density of the laser beam. The least carbon content is around 0.4 wt% in the carburized zone where austenite becomes the leading phase. Delta ferrite is found in a cellular carburized area, which resembles a duplex microstructure. The hardness of carburized zone has been at least increased by 130%, the yield strength and ultimate tensile strength of a fully carburized sample can be increased by respectively 90% and 85%. This hardening effect is driven by the precipitation of carbides formed during solidification offering pinning points for dislocations and grain boundaries. These improvements could be useful to modify locally ferritic stainless steel to meet industrial needs such as wear-resistant surfaces.