Strengthening mechanisms in a new precipitation hardening stainless steel fabricated by laser powder bed fusion

The microstructural properties and strengthening mechanisms in precipitation strengthening Corrax stainless steel manufactured by laser powder bed fusion have been investigated. The as-printed sample initially contains a fully martensitic microstructure. However, aging heat treatment triggered the formation of austenite laths between the martensitic structure. Despite having softer reverted austenite, Corrax showed excellent hardness and strength due to the formation of Ni- and Al-rich, spherical precipitates (with an average size of 4.27 +/- 1.20 nm). The atom probe tomography analysis reveals that Cr, Mo and Si are segregated in the Fe-based martensitic matrix, while the Mn diffused to the Al- and Ni-rich precipitates.