Simultaneous enhancements of strength and ductility of a selective laser melted H13 steel through inoculation treatment

Recent studies have confirmed that the high brittleness and property anisotropy of the selective laser melting (SLM) fabricated H13 tool steel are attributed to the presence of elongated, unstable high carbon γ (austenite) thin films in between the columnar structures. To overcome this problem, TiN nanoparticles (0.5 wt.%) were used as an inoculator to promote heterogeneous nucleation of the prior γ-grains, converting the columnar structure into equiaxed and refined grains. As a result, the finer α’-blocks formed upon the subsequent martensitic transformation. This not only leads to the elimination of the property anisotropy, but also simultaneously increases the strength (tensile strength of 2051 ± 48 MPa) and ductility (elongation of 7.4 ± 0.7%) of the SLM-fabricated H13 steel. The present work forms a significant step towards to fabricating high-performance tool steels using the SLM technique.