Selective laser melting (SLM) is an additive manufacturing process for the direct fabrication of
prototypes, tools and functional parts. The process uses a high intensity laser beam to selectively
fuse fine metal powder particles together in a layer-wise manner by scanning cross-sections
generated from a three-dimensional CAD model. The SLM process is capable of producing near
fully dense functional products without almost any geometrical limitation and having mechanical
properties comparable to those produced by conventional manufacturing techniques. There is a
wide range of materials that are suitable to be processed by SLM including various steels, Ti, Al
and CoCr alloys. Being one of these materials, maraging steel 300 (18Ni-300) is an iron-nickel
steel alloy which is often used in applications where high fracture toughness and strength are
required or where dimensional changes have to remain at a minimal level, e.g. aircraft and
aerospace industries for rocket motor castings and landing gear or tooling applications. To
achieve its superior strength and hardness, maraging steel, of which the name is derived from
‘martensite aging’, should be treated with an aging heat treatment. In this study, the effect of the
SLM parameters (scan speed and layer thickness) on the obtained density, surface quality and
hardness of maraging steel 300 parts is investigated. Moreover, various aging heat treatments
(different combinations of duration and maximum temperature) are applied on the SLM parts to
achieve high hardness values. The mechanical testing of maraging steel 300 specimens produced
by SLM and treated with an appropriate aging treatment is accomplished by impact toughness
and tensile tests and compared to the results obtained using conventional production techniques.
Additionally, the microstructures of as-built and heat treated parts are investigated.Mechanical Engineerin
