Achieving high strength in 430 stainless steel by laser powder bed fusion: microstructure-property relationships and strengthening strategies

Conventional manufacturing of 430 ferritic stainless steel faces significant challenges, including severe work hardening, rapid tool wear, and limited strengthening via heat treatment. To overcome these limitations, this study employs laser powder bed fusion (LPBF) technology to fabricate high-density (99.93%) 430 stainless steel samples through systematic process parameter optimisation. The as-built samples exhibit a unique microstructure characterised by columnar ferrite grains with a fibre texture along the building direction and a few oxides enriched in aluminium, oxygen, and nitrogen. In terms of mechanical properties, the as-built sample exhibits high yield strength of approximately 747.5 MPa, nearly double that of the conventionally hot rolled counterpart, while maintaining considerable ductility (∼29.2%). This significant strengthening is primarily attributed to the high-density dislocations generated during the LPBF forming process. This work demonstrates the potential of LPBF for producing high-performance ferritic stainless steels with enhanced mechanical properties.