Optimizing microstructure and mechanical properties in additively manufactured 18Ni (300) maraging steel by controlling strengthening agents

This study investigated the microstructural and mechanical behavior of ultrahigh-strength 18Ni (300) maraging steel manufactured using laser powder bed fusion (L-PBF) and subjected to various heat treatments (HTs). Four distinct HTs, including direct aging (DA), solution treatment with aging (S-A),...

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Main Authors: Mohammed Ali, Ali Khosravifard, Antti Järvenpää, Jukka Kömi, Atef Hamada
Format: Article
Language:English
Published: Elsevier 2025-06-01
Series:Materials & Design
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Online Access:http://www.sciencedirect.com/science/article/pii/S0264127525005349
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author Mohammed Ali
Ali Khosravifard
Antti Järvenpää
Jukka Kömi
Atef Hamada
author_facet Mohammed Ali
Ali Khosravifard
Antti Järvenpää
Jukka Kömi
Atef Hamada
author_sort Mohammed Ali
collection DOAJ
description This study investigated the microstructural and mechanical behavior of ultrahigh-strength 18Ni (300) maraging steel manufactured using laser powder bed fusion (L-PBF) and subjected to various heat treatments (HTs). Four distinct HTs, including direct aging (DA), solution treatment with aging (S-A), cyclic austenitization with aging (CA-A), and solution treatment prior to both CA and A (S-CA-A), were designed based on thermodynamic calculations and dilatation tests to enhance strengthening mechanisms. Microstructural characteristics were analyzed through electron backscatter diffraction, transmission electron microscopy, electron probe microanalysis, and X-ray diffraction. Mechanical properties such as hardness, tensile strength, and impact toughness were evaluated and correlated with the microstructure. The DA treatment significantly refined the microstructure and promoted austenite reversion, while the CA-A treatment resulted in a coarser structure with higher austenite content. The DA and CA-A treatments provided an optimal combination of strength (2 GPa) and moderate ductility (6%). Physical models were utilized to relate yield strengths to microstructural characteristics, highlighting the strengthening effect of second-phase particles. Empirical equations based on power law and exponential functions were assessed for modeling strain-hardening behavior. CA increased austenite fractions, with CA-A and S-CA-A cycles showing 43.7% and 46.3%, respectively. Laves-phase particles reduced the steel’s impact energy absorption, decreasing toughness.
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spelling doaj-art-0ceac723e3504412a69b2dffab8a8f7a2025-08-20T03:11:25ZengElsevierMaterials & Design0264-12752025-06-0125411411410.1016/j.matdes.2025.114114Optimizing microstructure and mechanical properties in additively manufactured 18Ni (300) maraging steel by controlling strengthening agentsMohammed Ali0Ali Khosravifard1Antti Järvenpää2Jukka Kömi3Atef Hamada4VTT Technical Research Centre of Finland Ltd, Visiokatu 4, P.o. box 1300, Tampere 33101, Finland; Steel Technology Department, Central Metallurgical Research and Development Institute, Helwan 11421 Cairo, Egypt; Corresponding author at: VTT Technical Research Centre of Finland Ltd, Visiokatu 4, P.o. box 1300, Tampere 33101, Finland. Tel.: +358 46 9417841.Department of Materials and Metallurgical Engineering, Abadeh Higher Education Center, Shiraz University, Abadeh 73916, IranFuture Manufacturing Technologies FMT, Kerttu Saalsti Institute, University of Oulu, Pajatie 5, Nivala FI-85500, FinlandMaterials and Mechanical Engineering, Centre for Advanced Steel Research, University of Oulu, P.O. Box 4200, FI-90014 Oulu, FinlandFuture Manufacturing Technologies FMT, Kerttu Saalsti Institute, University of Oulu, Pajatie 5, Nivala FI-85500, Finland; Corresponding author at: Kerttu Saalasti Institute, Future Manufacturing Technologies (FMT), University of Oulu, Nivala, FI-85500, Finland. Tel.: +358 45 251 6553.This study investigated the microstructural and mechanical behavior of ultrahigh-strength 18Ni (300) maraging steel manufactured using laser powder bed fusion (L-PBF) and subjected to various heat treatments (HTs). Four distinct HTs, including direct aging (DA), solution treatment with aging (S-A), cyclic austenitization with aging (CA-A), and solution treatment prior to both CA and A (S-CA-A), were designed based on thermodynamic calculations and dilatation tests to enhance strengthening mechanisms. Microstructural characteristics were analyzed through electron backscatter diffraction, transmission electron microscopy, electron probe microanalysis, and X-ray diffraction. Mechanical properties such as hardness, tensile strength, and impact toughness were evaluated and correlated with the microstructure. The DA treatment significantly refined the microstructure and promoted austenite reversion, while the CA-A treatment resulted in a coarser structure with higher austenite content. The DA and CA-A treatments provided an optimal combination of strength (2 GPa) and moderate ductility (6%). Physical models were utilized to relate yield strengths to microstructural characteristics, highlighting the strengthening effect of second-phase particles. Empirical equations based on power law and exponential functions were assessed for modeling strain-hardening behavior. CA increased austenite fractions, with CA-A and S-CA-A cycles showing 43.7% and 46.3%, respectively. Laves-phase particles reduced the steel’s impact energy absorption, decreasing toughness.http://www.sciencedirect.com/science/article/pii/S0264127525005349Additive manufacturingMaraging steelHeat treatmentAustenite reversionMicrostructure optimizationStrengthening precipitates
spellingShingle Mohammed Ali
Ali Khosravifard
Antti Järvenpää
Jukka Kömi
Atef Hamada
Optimizing microstructure and mechanical properties in additively manufactured 18Ni (300) maraging steel by controlling strengthening agents
Materials & Design
Additive manufacturing
Maraging steel
Heat treatment
Austenite reversion
Microstructure optimization
Strengthening precipitates
title Optimizing microstructure and mechanical properties in additively manufactured 18Ni (300) maraging steel by controlling strengthening agents
title_full Optimizing microstructure and mechanical properties in additively manufactured 18Ni (300) maraging steel by controlling strengthening agents
title_fullStr Optimizing microstructure and mechanical properties in additively manufactured 18Ni (300) maraging steel by controlling strengthening agents
title_full_unstemmed Optimizing microstructure and mechanical properties in additively manufactured 18Ni (300) maraging steel by controlling strengthening agents
title_short Optimizing microstructure and mechanical properties in additively manufactured 18Ni (300) maraging steel by controlling strengthening agents
title_sort optimizing microstructure and mechanical properties in additively manufactured 18ni 300 maraging steel by controlling strengthening agents
topic Additive manufacturing
Maraging steel
Heat treatment
Austenite reversion
Microstructure optimization
Strengthening precipitates
url http://www.sciencedirect.com/science/article/pii/S0264127525005349
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