Maraging Steel Research Articles

Studies on multiple weld repairs of M250 maraging steel for solid motor casing used in satellite launch vehicle application

Studies on multiple weld repairs of M250 maraging steel for solid motor casing used in satellite launch vehicle application

Programmable mechanical properties of additively manufactured novel steel

Abstract Tailoring thermal history during additive manufacturing (AM) offers a feasible approach to customise the microstructure and properties of materials without changing alloy compositions or post-heat treatment, which is generally overlooked as it is hard to achieve in commercial materials. Herein, a customised Fe-Ni-Ti-Al maraging steel with rapid precipitation kinetics offers the opportunity to leverage thermal history during AM for achieving large-range tunable strength-ductility combinations. The Fe-Ni-Ti-Al steel was processed by laser-directed energy deposition (LDED) with different deposition strategies to tailor the thermal history. As the phase transformation and in-situ formation of multi-scale secondary phases of the Fe-Ni-Ti-Al steel are sensitive to the thermal histories, the deposited steel achieved a large range of tuneable mechanical properties. Specifically, the interlayer paused deposited sample exhibits superior tensile strength (~1.54 GPa) and moderate elongation (~8.1%), which is attributed to the formation of unique hierarchical structures and the in-situ precipitation of high-density η-Ni3(Ti, Al) during LDED. In contrast, the substrate heating deposited steel has an excellent elongation of 19.3% together with a high tensile strength of 1.24 GPa. The achievable mechanical property range via tailoring thermal history in the LDED-built Fe-Ni-Ti-Al steel is significantly larger than most commercial materials. The findings highlight the material customisation along with AM’s unique thermal history to achieve versatile mechanical performances of deposited materials, which could inspire more property or function manipulations of materials by AM process control or innovation.

Innovative D-process MIG welding for enhanced performance of thick sections of MDN 250 in aerospace applications

Maraging steel, known for its exceptional strength, toughness and ductility, is widely used in aerospace and hypersonic missile manufacturing. The present study investigates the feasibility of joining 12 mm thick sections of maraging steel using advanced D-Process MIG welding technology. The D-Process integrates different welding modes such as MIG, Single Pulse-MIG and Double Pulse-MIG to optimize welding parameters, minimizing heat input. Additionally, the research investigates the influence of various post-weld heat treatments (PWHTs) on the performance of welded joints. The PWHTs included in the study are Ageing Treatment (AT), Solution Treatment + Ageing Treatment (SAT) and Homogenizing Treatment + Solution Treatment + Ageing Treatment (HSAT). Metallographic and mechanical tests were conducted on as-welded (AW) and PWHT conditions. Results showed the HSAT condition yielded superior properties with an average UTS of 1771 MPa, YS of 1734 MPa, and an average fracture toughness (FT) of 88 MPa√m. This underscores the efficacy of D-Process welding in meeting stringent requirements for maraging steel in aerospace and high-performance applications.

Interaction between inclusions and the TRIP effect during tensile loading of an L-PBF 18Ni-300 maraging steel and effect on ductility

The influence of non-metallic inclusions on the tensile ductility of a direct aged 18Ni300 maraging steel produced by L-BBF was investigated on two materials having the same microstructure and a different content of non-metallic inclusions. The strain-induced transformation of austenite promotes the TRIP effect enhancing ductility. In the presence of a high amount of inclusions, the minimum strain needed to trigger strain-induced transformation is reached after necking, and the transformation cannot contribute to ductility. The effect of inclusions is to promote stress rising and strain accumulation, but mostly to make TRIP uneffective. To recover the effectiveness of TRIP and, in turn, increase ductility, the stability of reverted austenite should be reduced, in order to anticipate its transformation in martensite that is able to extend the uniform deformation step.

Study on mechanical behaviour and microstructure evolution of wire-arc directed energy deposition Co-free maraging steel under dynamic compression

ABSTRACT The dynamic compression property of maraging steel is an important basis for determining the impact resistance of the structure, and the related studies are few. To enrich the relevant data and elucidate the relevant mechanisms, in this work, a new Co-free maraging steel component is fabricated by wire-arc direct energy deposition (DED), and the quasi-static tensile properties and dynamic compression properties are tested. The results show that the deposition direction exhibits the highest quasi-static tensile properties. Strain rate strengthening effect, grain refinement and grain boundary strengthening are the main strengthening mechanisms during dynamic compression. With the increase of strain rate, dynamic recrystallization intensifies, causing the grain size and dislocation density to decrease. Under dynamic condition, strain-induced martensite phase transformation reduces the austenite content; temperature rise and dynamic recrystallization limit the degree of martensite phase transformation. Strain rate sensitivity of the strength is independent of the direction.

Solute and phase heterogeneous distribution at different scales and its effect on ageing physical phenomena in a laser powder bed fusion produced maraging steel

The Laser Powder Bed Fusion process involves complex thermodynamic and heat transfer mechanisms which results in a complicated understanding of the material’s microstructure and phase transformation processes. In the case of additive manufacturing maraging steels, these present heterogeneous structures which mainly consist of Body-Centred Tetragonal (BCT) martensite and retained austenite (Face-Centred Cubic (FCC) phase structure), unlike conventionally processed material. Research has already been done on the competitive or collaborative nature of austenite growth/reversion and precipitation in these materials. However, for Laser Powder Bed Fusion maraging steels, studies have focused on either the effect of the heterogeneous structures on austenite reversion kinetics or the formation, evolution and behaviour of precipitation. Still, no comprehensive research exists that covers in detail the relation between solute heterogeneity from the meso- to the nanoscale and its influence on both phase distribution and ageing physical phenomena. To do so, multiscale chemical analyses and microstructural characterisation techniques were used to investigate a maraging steel M300 in different transformed conditions: as-built, aged at 480 and 540 °C. The results showed that competing mechanisms during printing caused segregation at the mesoscale, which remains in aged samples. Vaporisation led to Cr segregation, while melt convections caused Ni and Ti depletion at melt pool boundaries. Retained austenite location was found at melt pool boundaries and away from them on the as-built structure. Its preferential location remains unclear. Dissimilarities from conventional material were identified in nanosized clustering and precipitates on aged samples.

Characterisation of 18Ni 300 steel CT specimens in a fatigue test manufactured by selective laser melting at 0°, 45° and 90°

Maraging steel, 18Ni300, is a high-performance material that shows promising potential for various industrial applications. Employing Selective Laser Melting, it is utilized in the production of high-value components. Understanding the fatigue mechanisms of this material is imperative, as its fatigue life is influenced by both surface and internal porosity, as well as defects produced when manufacturing the objects due to the patterns used. The main objective is to analyze the characterization of these pores and clarify their relationship with the fatigue properties of the material under study. Compact tension specimens were manufactured by selective laser melting at three angles (0°, 45° and 90°) with respect to the crack growing direction and fatigue tests were performed. A study of the porosity of the sample was conducted, which established a correlation between the printing angle, growing rate (da/dN curves), and the porosity that is categorised through the aspect ratio and the circularity ratio. It is shown that all manufacturing orientations generate similar pore sizes and area, but the 45° orientation induces pore with slightly higher circularity ratio. The results indicate that the faster fatigue crack growth might be linked to the slight increase in circularity, and this was observed for 45°.

Mechanical Properties and Microstructure of Laser Powder Bed Fusion‐Processed 18Ni300 Maraging Steel According to Direct Aging Treatment Conditions

The nonequilibrium microstructures produced by laser‐based additive manufacturing can enhance the mechanical properties of metallic alloys. However, the optimal post‐treatment conditions will change according to the initial microstructure induced by the manufacturing process employed. Therefore, this study investigates the optimal direct aging conditions for the post‐treatment of laser powder bed fusion‐processed 18Ni300 maraging steel by changing the aging temperature and time. The aging time required to achieve maximum tensile strength decreased as the aging temperature increased, and an increase in the aging temperature accelerated the evolution of nanoscale precipitates. The results indicate that the optimal direct aging conditions of 520 °C for 2 h achieved the largest tensile strength (≈2100 MPa) and precipitate area fraction. Notably, the reduced aging time at this temperature compared with that under conventional aging conditions (8 h at 460 °C or 490 °C) minimizes the thickening of the (Mo,Ti)‐rich segregation, which otherwise contributes to austenite reversion and strength reduction owing to overaging. Thus, the optimal direct aging conditions for additively manufactured maraging steel components are different from those for conventionally produced maraging steel components. This understanding of the microstructural changes induced by direct aging according to the initial non‐equilibrium state provides vital information for enhancing the performance of additively manufactured metallic alloys.

Influence of hybrid additive manufacturing processes on the microstructure and mechanical properties of maraging steel 1.2709 components with post-processing heat treatments

The microstructural analysis revealed that the hybrid manufacturing process, combining Powder Bed Fusion (PBF) and Directed Energy Deposition (DED), resulted in a refined grain structure with a uniform phase distribution in the Maraging Steel 1.2709 components. The post-processing heat treatments, specifically stress relief at 500 °C for 2 h and solution treatment at 850 °C for 2 h, significantly enhanced the material’s mechanical properties. The components exhibited increased hardness and improved tensile strength, attributed to the effective elimination of residual stresses and the promotion of desirable precipitate formation during heat treatment. Overall, the study demonstrated that the hybrid PBF-DED process, coupled with appropriate heat treatments, can produce maraging steel components with superior mechanical performance, making them suitable for high-stress applications in advanced manufacturing sectors.

Surface characteristics of maraging steel during electropolishing as a function of polishing time

ABSTRACT Thermal-based machining process like EDM, Laser-assisted additive manufacturing process degrades the surface integrity of the component. Therefore, a post-polishing method is required to improve the surface integrity as well as the performance of the component. A gyroscope, made of maraging steel, fabricated by EDM, is utilised in space industry and has poor surface integrity, which affects its performance. Thus, electropolishing (EP), a non-conventional polishing process, is used for the above said problem as it possesses several advantages over other polishing methods. There are very few literatures available for EP of maraging steel. The present manuscript is the preliminary analysis for the electrolyte (Ortho-phosphoric acid, sulphuric acid and hydrochloric acid) and its effect on maraging steel with respect to time. The surface characteristics such as surface roughness and surface reflectivity, along with surface elemental composition, have been evaluated. With increase in time, maximum improvement in surface roughness and surface reflectivity is 61.23% and 70%, respectively. It can be concluded that the selected electrolyte gives a promising improvement in the surface characteristics of maraging steel.

Особенности применения электродов-инструментов, изготовленных аддитивными технологиями, при электроэрозионной обработке изделий

Introduction. The paper presents the results of a study of the use of a tool electrode (TE), manufactured by selective laser alloying from MS1 maraging steel powder for copy-piercing electrical discharge machining (EDM). Purpose of the work: experimental study of the features of the use of additively manufactured TE in the EDM of critical products. Research methods. The specimens were prepared using a ReaLizer SLM 50 system. The starting material was spherical MS1 powder with an average particle size of 30 μm. To test the modes and select a TE sample with the least number of surface defects, four manufacturing modes were tested, and the best TE sample was selected for further research. The EDM was carried out on EMT Smart CNC equipment in a dielectric oil environment. The specimens were installed in a clamp with straight polarity and were used as TE; a 0.12C-18Сr-10Ni-Тi steel plate served as the workpiece electrode. The study was conducted using a factorial experiment (type 23) with a central design. The input data of the factorial experiment is the current I (A), voltage U (W), pulse on time Ton (μs). The output parameters were the roughness parameter Ra and tool electrode wear γ. The roughness parameter Ra was measured using a Mahr Perthometer S2. Results and discussion. TE samples were made from MS1 powder using the SLS method; the highest quality TE sample No. 4 was selected for EDM. Empirical equations are obtained that describe the relationship between the roughness parameter Ra and tool electrode wear γ, depending on the EDM modes. At the minimum mode with a current I = 4 A and a voltage U = 50 V, the tool electrode wear is γ = 0.0063875 g. The maximum tool electrode wear is γ = 0.13938 g with a current I = 8 A and a voltage U = 50 V. It is established that at a constant pulse on time Ton = 75 μs, the smallest roughness Ra = 2.83 μm is obtained at a current of I = 4 A and a voltage U = 100 V, and the maximum roughness is Ra = 4.1568 μm at I = 8 A and U = 100 V.

Influence of phase transformation coefficient on thermomechanical modeling of laser powder bed fusion for maraging 300 steel

Manufacturing maraging steel components using laser-based powder bed fusion (LPBF) presents an attractive proposition for industries due to the material's combination of mechanical properties such as hardness, wear resistance, toughness and the capability to produce parts with complex geometries and high precision. Despite these advantages, the LPBF process induces defects such as distortion and residual stress associated with the complex thermal cycles, compromising final part quality. Numerical simulations have been developed to predict these defects. However, LPBF simulations remain challenging due to the complexity of the process and the substantial computational resources required. For maraging steel, for example, the occurrence of phase transformation promotes compressive stress that interferes in results and makes simulations inaccurate. This research aims to simulate a geometry with a circular inner channel and investigate distortion, volume fraction of martensite and equivalent stress results. Modeling was performed by varying phase transformation rate parameters to assess the impact of transformations on simulation outcomes. Results showed minimal impact of these parameters on distortions and equivalent stress. Equivalent stress results were compared with literature findings, while distortion results were validated against experimental data to validate the accuracy of the model.

Influence of post heat treatment on tribological and microstructural properties of plasma wire arc additive manufactured maraging steels

Abstract Metallic alloys are increasingly being produced using wired arc additive manufacturing (WAAM). In this study, 18Ni300 defect-free maraging steels were produced using the WAAM technique. A traditional solution treatment, direct aging, and cryogenic heat treatment processes were applied to the WAAM produced maraging steels. The influence of conventional and novel cryogenic heat treatments on microstructural, mechanical, and tribological properties were examined. The microstructure of the as-built materials obtained by WAAM thermal cycling has mainly been homogenized through the solution, direct-aging, and cryogenic heat treatments. As a result, homogeneously distributed precipitate phases were obtained and the hardness increased by 30 % with a combination different post heat treatments. The cryogenic heat treatment improved the martensitic transformation and facilitated the formation of various Fe–Ni–Mo–Ti-containing intermetallic precipitates. Similarly, because of the different heat treatments, the wear resistance improved by a factor of 2–5.5 relative to the as-built material. Adding the cryogenic heat treatment to the traditional heat treatment procedure improves wear resistance by a factor of 1.2–2.9.

Experimental investigation of heat treatments on the mechanical performance of grade 300 maraging steel strut-based lattices

Lightweight and strong components are essential for reducing energy consumption and enhancing efficiency. Lattice structures are one such geometry utilized to achieve weight reduction. This study investigates the mechanical properties of various lattice structures fabricated from Maraging Steel (EOS MS1) using the Direct Metal Laser Sintering (DMLS) method. The samples include three distinct cellular geometries: body-centered cubic (BCC), face-centered cubic (FCC), and octet truss configurations, which are subjected to tensile and compressive tests. The primary goal of this research is to evaluate the impact of heat treatment on the mechanical properties of cellular architecture under tensile and compressive loading conditions. Destructive, nondestructive testing, and simulation results were also obtained from different heat treatment processes. It was found that the age-hardened specimens performed the best overall in terms of ultimate tensile/compressive strength and elongation. The top-performing topologies in compression and tension were found to be the octet structure, as they were able to withstand the most loading and straining when compared to the other specimens.

Modeling of the hot-deformation behavior of Fe-Ni-Al maraging steel using constitutive equations and machine learning algorithms

Modeling of the hot-deformation behavior of Fe-Ni-Al maraging steel using constitutive equations and machine learning algorithms

Microstructural evolution and mechanical properties of maraging steel by additive manufacturing

Laser powder bed fusion (LPBF) is a revolutionary and innovative technology that provides advanced technical support for the forming of parts with high precision and complex structures. In this work, a new type of Fe-Ni-Mo-Ti-Al-Y cobalt-free maraging steel was successfully fabricated by LPBF. The additive manufacturing parameters and the microstructural evolution of cobalt-free maraging steel under different heat treatment parameters were systematically studied. The results show that the parts without cracks and close to complete density can be fabricated under a wide LPBF process window. The dislocation cell with 500 nm in the printing state makes the material have good plasticity. After post-heat treatment, the preferred orientation of LPBF maraging steel is reduced, but the typical characteristics of molten pool and cellular structure in maraging steel disappeared, which is the result of local composition and microstructure homogenization. The elongation of LPBF maraging steel in solution annealed state is higher than that in as-printed state, which is due to the reduction of dislocation density and grain coarsening. However, after direct aging, due to the formation of nano-sized Ni3(Ti, Mo) precipitates in the matrix, the mechanical properties of the material were effectively enhanced, and the tensile strength increases from ∼1.1 GPa in as-printed state to ∼1.6 GPa in aging state. In contrast, the corrosion resistance of as-printed maraging steel is higher and comparable to that of traditional cobalt-containing maraging steel. However, the corrosion resistance of LPBF maraging steel after being aged is reduced, which is due to the existence of precipitates and dislocations. This study provides a theoretical reference for the composition design and strengthening mechanism of LPBF cobalt-free maraging steel.

The effect of thermal cycle on microstructure evolution and mechanical properties of Co-free maraging steel produced by wire arc additive manufacturing

Microstructures and mechanical properties are closely related to thermal cycles during additive manufacturing. For maraging steel, the research on the effect of thermal cycles during additive manufacturing is limited. Based on the above issues, this work investigated the effect of thermal cycles in the process of wire arc additive manufacturing Co-free maraging steel on microstructure evolution and mechanical properties, and attempted to establish the relationship between thermal cycles and microstructure as well as mechanical properties of maraging steel on the basis of quantitative thermal cycle data. The results show that in the additive manufacturing process, the thermal cycles affect the cooling rate, so that the primary dendrite arm spacing and grain size gradually increase along the height direction. For maraging steel, in additive manufacturing, welding or other hot processing processes, the thermal cycles make the martensite reverse change, resulting in an increase in austenite content, resulting in grain refinement. Thermal cycles in additive manufacturing result in differences in the grain size, grain boundary ratio, dislocation density and primary dendrite arm spacing, resulting in inhomogeneity of the mechanical properties in the height direction. The difference in microstructure in different directions of additive manufacturing samples leads to anisotropy of tensile properties. The results of this work can elucidate and refine the action mechanism of thermal cycles on maraging steel. In addition, this work can be used to control thermal cycles by changing the process and cooling conditions, etc., to obtain maraging steel samples with homogeneous or gradient properties, which is highly important.

Effect of heat treatment on the microstructure and mechanical properties of 18Ni 300 maraging steel manufactured by wire + arc additive manufacturing

ABSTRACT A thin-walled structure was manufactured by wire + arc additive manufacturing using 18Ni 300 maraging steel, and the heat treatment process had been investigated. The microstructure of as-deposited sample was martensite, ferrite and nano-precipitated phases. Differently, more nano-precipitated phases and reverted austenite existed in the direct aging (AT) sample. However, only lath martensite and nano-precipitated phases existed in the solution + aging (SAT) sample. The as-deposited and AT samples performed a high strength with well plastic. The primary strengthening mechanism for this great improvement of tensile strength arose by the formation of nano-precipitated phases, which was known as the Orowan strengthening mechanism. The well plastic of as-deposited and AT samples was attributed to dual phase net basket sub-structures, which were beneficial to improve the length of crack propagation and the ability of cooperative deformation. And the reverted austenite was also main factor for the well plastic of the AT samples.

Selective Laser Melting: A Novel Method for Surface Roughness Analysis

The present study introduces a novel approach to analyse the surface roughness of metal parts made by 3D selective laser melting (SLM). This technology, known for its ability to efficiently produce functional prototypes and limited-run series, is particularly effective when surface conditions directly meet usage requir ements. Thus, the suitability of surfaces is a critical factor, emphasizing the importance of new methods for predicting their quality. Here fractal geometry and network theory are integrated to delve into the complexities of SLM-produced surfaces, while machine learning and pattern recognition concepts are employed to evaluate the surface roughness. Specifically, genetic programming, artificial neural networks, support vector machine, random forest, k-nearest neighbors are compared in terms of accuracy demonstrating that only the first method provided valid estimation due to the presence of very little training data. Experimental work with EOS Maraging Steel MS1 and an EOS M 290 3D printer validates the method’s practicality and effectiveness. Then, the research offers a fresh perspective in surface analysis and has significant implications for quality control in additive manufacturing, potentially enhancing the precision and efficiency of 3D metal printing.

Effect of Direct Aging Heat Treatment on Microstructure and Mechanical Properties of Laser Powder Bed Fused Maraging Steel 300-Grade Alloy

Abstract This paper investigates the effects of a 6-hour direct aging heat treatment at 490 °C on the mechanical, tribological, and microstructure characteristics of laser powder bed fused maraging 300 steels, which is produced at various laser energy densities. After direct aging heat treatment, the grain boundaries become irregular and vague due to the residual stress releasing, squeezing of precipitates into the grain boundaries, and phase transformations. The XRD analysis reveals the reverted austenite (γ′) phase forms during aging treatment due to the inevitable reversion of metastable martensite to the stable reverted γ′ phase. The heat-treated samples' microhardness rises with rising the laser energy density (LED) from 61.41 to 92.10 J/mm3 due to a decrease in the reversed austenite phase and a further rise in LED decreases the microhardness of heat-treated samples due to a rise in the reversed austenite phase after heat treatment. The heat-treated sample produced at LED of 92.10 J/mm3 shows maximum yield, ultimate tensile strengths, and minimum elongation percentage due to its high microhardness, and the fractography results show the failure mode as a mixed brittle and ductile fracture. The wear-rate of the heat-treated additively manufactured maraging 300 steel decreases as the LED increases from 61.41 to 92.1 J/mm3 and a further rise in LED from 92.10 J/mm3 to 166.66 J/mm3, the wear-rate increases. The wear-rate rises with a rise in sliding velocity from 1.5–3.5 m/s. The dominant wear mechanism was observed as abrasion with small grooves and saplings.