Boride precipitation and mechanical behaviour of high boron stainless steel with boron and titanium additions

High boron stainless steel (HBSS) was produced by vacuum induction melting (VIM) technique. The effects of boron and titanium on the microstructure and mechanical properties of the HBSS were investigated. The results show that the boron can be formed into Fe1.1Cr0.9B0.9 boride particulates which lead to poor mechanical properties, especially the ductility, of the as-cast HBSS. With the boron content of the as-cast HBSS increased from 0.4 wt. % to 1.4 wt. %, the elongations to rupture (Er) and the impact toughness decrease from 7.8% and 11.45 J/cm2 to 2.3% and 4.21 J/cm2, respectively. The formation of TiB2, which replaces most of the prior Fe1.1Cr0.9B0.9 boride particulates, benefits the refinement of the microstructures and the improvement of the mechanical properties. The impact toughness of the as-rolled and then heat treated HBSS, what's more, has tremendous increase from 28.1 J/cm2 to 42.6 J/cm2.