en گروه سرامیک Ceramic Materials and Engineering Research Paper Research Paper <span style="font-size:11pt"><span style="line-height:200%"><span style="font-family:Calibri,sans-serif"><span style="background:lime"><span new="" roman="" style="font-family:" times=""><span style="background-color:#ffffff;">Selective</span></span></span><span style="font-size:12.0pt"><span style="background:lime"><span style="line-height:200%"><span new="" roman="" style="font-family:" times=""><span style="background-color:#ffffff;"> laser melting (SLM) is a widely used additive manufacturing method for 3D-printing metal parts. This study investigates how SLM parameters affect the density, microstructure, and mechanical properties of maraging steel 300. A process window was developed, revealing that maximum density and minimal porosity are achieved when laser energy density exceeds 50 J/mm&sup3;. Optimal parameters&mdash;100 mm/s scan speed, 20 &mu;m layer thickness, 0.15 mm hatch distance, Stripe scanning strategy, and XZ build direction&mdash;were identified. Optimal processing reduced porosity, increased martensite content, and enhanced strength, reaching 1064 MPa and improving by 75% to 1862 MPa after aging and solution treatment. Strength gains were attributed to the uniform dispersion of nano-sized precipitates </span></span></span></span></span><span style="background:lime"><span new="" roman="" style="font-family:" times=""><span style="background-color:#ffffff;">(such as Ni(Mo)</span>_{<span style="background-color:#ffffff;">3</span>}<span style="background-color:#ffffff;"> and Ni(Ti, Al)</span>_{<span style="background-color:#ffffff;">3</span>}<span style="background-color:#ffffff;">) </span></span></span><span style="font-size:12.0pt"><span style="background:lime"><span style="line-height:200%"><span new="" roman="" style="font-family:" times=""><span style="background-color:#ffffff;">within the martensitic matrix. Additionally, it was found that higher cooling rates further improve the mechanical strength of heat-treated parts.</span></span></span></span></span></span></span></span><span style="background-color:#ffffff;">&nbsp;</span> Additive manufacturing,Selective laser melting,Maraging steel,Heat treatment,Microstructure 26 39 http://ijmse.iust.ac.ir/browse.php?a_code=A-10-5431-1&slc_lang=en&sid=1 Yaser Vahidshad y.vahidshad@isrc.ac.ir 1800319475328460020868 1800319475328460020868 Yes Iranian Space Research Center, Space Transportation Research Institute Karen Abrinia cabrinia@ut.ac.ir 1800319475328460020869 1800319475328460020869 No University of Tehran, College of Engineering / Faculty of Mechanical Engineering