Selective laser melting fabricated carbon nanotube reinforced 18Ni300 maraging steel directly used for mold repairing

The extreme working conditions of 18Ni300 Maraging steel (MS) lead to the damage of molds, thus there is a constant demand of mold repairing. However, neither medium carbon steels nor 18Ni300 MS itself can ensure better compatibility with the aged-18Ni300 MS substrate. Therefore, 0.2 wt.% CNTs were added to form 18Ni300/CNT composite through selective laser melting (SLM). This addition refines the grain size and leads to the formation of (Ti, Mo)C carbides. Due to the grain refinement strengthening and precipitation strengthening, both tensile strength and elongation of 18Ni300/CNT composite improved in comparison to the as-built 18Ni300 MS. The impact toughness also increases from 46 ± 1.5 J/cm2 to 62 ± 2 J/cm2. The comparable mechanical properties between 18Ni300/CNT composite and aged-18Ni300 MS suggests that this composite can be directly used for mold repairing without post heat treatment, presenting a promising and cost-effective method to prolong the mold lifetime.