Ultrafine-grained stainless steel with wear-resistant nanoborides decorating grain boundaries produced by laser powder bed fusion

Stainless steel composites combine corrosion resistance and toughness of the metallic matrix with wear resistance granted by hard reinforcing nanoparticles. Given their near-net-shape manufacturing characteristics, additive manufacturing techniques are attractive to produce these hard and wear-resistant classes of materials with low machinability. In this work, from a SAF 2205 duplex stainless steel with boron addition, laser powder bed fusion (LBPF) was employed to produce an ultrafine-grained (∼1 µm), dense (porosity ∼0.1 %), and crack-free ferritic-induced matrix composite with Cr2B-nanoborides reinforcing the grain boundaries (GBs) without formation of Cr-depleted regions. The composite showed significant higher hardness (up to 456 HV0.5) and wear resistance (4.4 x 10−5 mm3 N−1 m−1) in sliding condition compared to a hot-rolled (225 HV0.5 and 2.9 x 10−3 mm3 N−1 m−1) and a LPBF-produced SAF 2205 (314 HV0.5 and 3.3 x 10−4 mm3 N−1 m−1).