Fabrication of lotus-type porous carbon steel by unidirectional solidification in nitrogen atmosphere

Lotus-type porous carbon steel AISI 1018 was fabricated by the continuous zone melting technique in pressurized nitrogen atmosphere. Cylindrical pores parallel to the solidification direction were observed in the porous carbon steel. The pore diameter and porosity can be controlled by the pressure of nitrogen. The nitrogen concentration in matrix of porous carbon steel fabricated under nitrogen pressure 2.5 MPa was 0.12 wt.%. The micro Vickers hardness increases with nitrogen pressure, which is attributed to the solid-solution hardening.