Additive manufacturing (AM) is the most remarkable manufacturing technology developed in recent years. With this technology, it can produce products directly from a computeraided design model. In this respect, AM technologies can provide parts in less time compared with traditional production methods by producing less waste with a shorter processing step and will be very important for future industry applications because of these features. [1-5] Selective laser sintering (SLS) is a process of bonding (sintering) powder particles to each other by exceeding the melting temperature utilizing a laser beam. SLS machines can be given different names. EOS GmbH (Germany) has described this process as direct metal laser sintering (DMLS). [6,7] DMLS is an advanced technology that enables the rapid production of complex-shaped 3D parts using metal powders. [8] DMLS has a unique ultrafine and metastable microstructure, thanks to its fast solidification rate (10 3-10 8 K s À1). [9] This rapid solidification results in high thermal gradients and short interaction time. Thus, the microstructures of DMLS-produced materials are different than those produced by conventional methods. Tool steels produced by AM methods also have microstructures that are quite different from traditional cast-tool steels. Due to the advantages of the SLS method, it is widely used in aerospace, medical, defense, and automotive industries. AlSi10Mg, titanium, stainless steels, composites, tool steels, and Ni-based alloys can be produced by the DMLS method. [10-15] The name "Maraging" comes from the combination of martensite and aging. [16] Maraging steels (MS1) are valuable materials due to their excellent formability, weldability, toughness, and high strength. Therefore, it is preferred in critical applications such as submarine bodies, gears, rocket engine cases, aircraft components, pressure vessels. [17-22] 18Ni-300 MS1 is used in the AM processes. MS1 is a steel that can be aged, and forms precipitates such as Ni 3 Mo, Ni 3 Al, Ni 3 Ti, Fe 2 Mo, etc. [23-30]. MS1 is a fascinating steel for engineering applications because of its good weldability, machinability, and surface treatment. MS1 produced with DMLS show low strength in as-built condition. Various heat treatments are applied to this material to increase strength. These heat treatments are directly aged from the as-built state (aged) and solution and after aging (SHT) heat treatments. [31,32] In the literature, MS1 studies that were produced by the SLM method have been done before, but these are limited. Also, no research has been done about MS1 produced by the DMLS
