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Faraz Deirmina,Sasan Amirabdollahian,Luke Harris,Eleonora Bettini,Raveendra Siriki,Massimo Pellizzari,Paolo Bosetti,Alberto Molinari 대한금속·재료학회 2023 METALS AND MATERIALS International Vol.29 No.10
Maraging steels are a class of low-carbon ultra-high-strength martensitic steels. Due to their excellent weldability, these steels have been widely applied for laser-based additive manufacturing (AM). MAR-60HRC is a newly developed maraging grade for AM with a nominal chemical composition of 13.0Ni-15.0Co-10.0Mo-0.2Ti, Fe bal. (wt%), capable of achieving hardness levels of ~ 740 HV. Alternatively, 18Ni300 is a commercialized maraging steel with an excellent combination of strength and toughness at the peak aged hardness (i.e., ~ 590 HV). This work aims to investigate the properties and microstructure of MAR-60HRC fabricated by Laser Directed Energy Deposition (L-DED). Further, the manufacturability of bimetallic parts comprising a tough 18Ni300 core and a hard MAR-60HRC on the surface was evaluated. After proper aging, the multi-layered material showed a surface hardness of ~ 720 HV1 and apparent fracture toughness of 71 MPa m1/2, higher than that of MAR-60HRC (i.e., 60 MPa m1/2), and lower than 18Ni300 (i.e., 90 MPa m1/2). The excellent combination of surface hardness and fracture toughness was discussed, considering the crack arrest at the interface and the flawless interface between the two steels.
Effect of Cr Contents and Heat Treating on Reverted Austenite in Maraging Steel Weldments
S. W. Kim,H. W. Lee 대한금속·재료학회 2018 METALS AND MATERIALS International Vol.24 No.3
By conducting fl ux cored arc welding (FCAW) on maraging steels with Cr contents of 1.4 and 5.2 wt%, this study observedthe eff ects of Cr content and heat treating on reverted austenite formation in welded maraging steel. Aging treatment wascarried out at the temperatures of 450, 480 and 530 °C for 3 h in each condition. As the aging temperature increased, revertedaustenite was formed along the interdendritic and intercellular grain boundaries, and the proportion of reverted austeniteincreased with increasing Cr addition. The aging process led to the segregation of Ti and Mo along the interdendritic andintercellular grain boundaries. Some of the welded specimens were subjected to solution heat treatment at 820 and 1250 °Cfor 1 h after welding, resulting in a decrease in reverted austenite fraction.
Optimal Process Conditions for Powder Bed Fusion and Analysis of Properties of Maraging Steel
A Ra Jo,Ji Seob An,Sun Hyung Kim,Dong Yong Park,Young Hoon Moon,Sun Kwang Hwang 대한금속·재료학회 2023 METALS AND MATERIALS International Vol.29 No.10
Powder bed fusion (PBF), an additive manufacturing technology, has been widely used in the manufacturing field to create complex designs. Most PBF process studies have investigated the effect of laser power and scan speed on the mechanical properties and porosity of microstructure. In this study, five process conditions were selected to obtain superior properties of maraging steel, which were validated by absolute density analysis, hardness, and tensile tests. Maraging steel exhibits diverse mechanical properties depending on the heat-treatment combinations of solution annealing and aging. Mechanical property tests were conducted to compare the various temperature properties of the fabricated maraging steel under optimal conditions. Maraging steel exhibited a hardness of 612.7 HV and a tensile strength of 1925.6 MPa at 25 °C, and the strength was greater than 1000 MPa at temperatures below 600 °C. Additionally, the applicability of a fabricated die for maraging steel was investigated. The maraging steel die and American Iron and Steel Institute (AISI) D2 were analyzed by a forging process based on die load data sensing with a piezoelectric bolt. The maximum loads of the sensor in horizontal and vertical directions were 24.7% and 15.8% lower for the fabricated die than those of AISI D2. The findings confirm that the fabricated maraging steel is a suitable manufacturing process for commercial processes and can be used to manufacture dies with complex shapes.
Influence of Segregation on Microstructure and Hot Workability of Grade 250 Maraging Steel
Hyungsoo Lee,Hi Won Jeong,Seong Moon Seo,Dae Won Yun,Kyungmi Park,Kwang Hyuk Yim,Young Soo Yoo 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.4
The optimal process parameters of grade 250 maraging steel for hot forging were investigated with a process map and microstructureanalysis. To generate the process map, hot compression tests were performed at 800–1200 °C and strain rates of0.01–5 s−1. The flow stress–strain curves were calibrated by Bayesian artificial neural network (ANN) modeling to compensatethe heat generated by dynamic deformation. The Ni and Mo segregation during the solidification of the ingot causedalternating layers of Ni- and Mo-rich and -lean bands, which affected the recrystallization behavior during hot compression. According to the calculated process map, 1100–1200 °C × 0.01–0.7 s−1 and 1000–1200 °C × 0.01–0.2 s−1 are favorableprocess conditions that ensure wide process windows in terms of strain rate and temperature, respectively. The commonfeatures of the microstructure deformed under both conditions were relatively coarse martensite blocks and low values in theelectron backscattered diffraction (EBSD) kernel average misorientation (KAM) results (i.e., low residual stresses), whichwere attributed to a low fraction of fine martensite block region.
가스질화처리 적용을 통한 스마트무인기 머레이징강 로터허브 부품 품질개선
이명규,최성욱,김재무,Lee, Myeong Kyu,Choi, Seong Wook,Kim, Jai Moo 항공우주시스템공학회 2014 항공우주시스템공학회지 Vol.8 No.2
Feathering spindle is one of the critical parts of the rotor system in the Smart Unmanned Aerial Vehicle(SUAV) that it was manufactured with special material, Maraging C300. During the initial ground and tie-down flight tests of the SUAV, surface of the feathering spindle contacting to the needle-roller bearings showed excessive wear and dent due to high vibrating loads transferred from the rotating blades. Gas nitriding process was applied to the bearing contact surface of the feathering spindle to increase surface hardness so as to improve the surface defects. This paper briefly presents the gas nitriding process adopted and the spindle quality improvements including wear and corrosion resistance.
이지훈(Jihoon Lee),박주성(Jusung Park),윤태건(Taegeon yun) 한국추진공학회 2016 한국추진공학회 학술대회논문집 Vol.2016 No.12
로켓 추진기관 외피인 연소관은 고압, 고온 등 가혹한 환경에 견뎌야 하기에 고강도 소재가 이용되며, 주로 소성가공을 통해 제작된다. 소성가공에는 다양한 방법이 있지만 고강도 소재를 이용하기 때문에 공정이 까다롭고 균일한 기계적 특성을 만족하는데 어려움이 있다. 본문에서는 고강도 소재의 추진기관 연소관 공정개발을 위해 설계를 최적화하고, 고강도 소재인 마레이징강을 이용하여 열간후방압출공정을 통해 연소관을 제작, 기계적 특성을 확인하였다. Case in Roket propulsion has to endure harsh environments, such as the high-pressure and high-temperature. So, it widely makes of material that high degree of strength and toughness steel through plastic deformation processes. Also, it is hard to satisfying uniform mechanical properties due to material of high strength. In this study, it is optimization of manufacturing process for development of Rocket propulsion case with maraging steel through hot backward extrusion. Also we evaluated the mechanical properties.
김석현(S. H. Kim),김명호(M. H. Kim),차용훈(Y. H. Cha) 한국생산제조학회 2011 한국생산제조시스템학회 학술발표대회 논문집 Vol.2011 No.4
In this study, response values were analyzed according to aging conditions using Design of Experiment and Response Surface Methodology in order to produce maraging steel with excellent mechanical properties. Aging treatment conditions were selected with temperature and time. Through response optimization, then, time and temperature of the most optimal response values were extracted.