Laser Direct Energy Research Articles

High-speed laser-directed energy deposition of crack-free wear-resistant and anti-corrosive Al/Cu bimetal components

ABSTRACT Al/Cu bimetal components (BMCs) possess higher thermal conductivity, better wear resistance and corrosion resistance than Al and Al alloys. It is a big challenging task to fabricate a high-performance Al/Cu BMC by a conventional infrared (IR) laser-directed energy deposition (L-DED) process due to the crack formation and high IR laser reflectivity. A novel high-speed L-DED process was proposed to successfully fabricate a crack-free Al/Cu BMC by controlling the residual stress distribution and brittle intermetallic compounds (IMCs) formation. The damaging effect of the reflective IR laser rays on the laser equipment can also be suppressed. Compared with the Al base metal, the microhardness, wear and electrochemical corrosion performances of the Al/Cu BMC were significantly improved. The residual stress distribution was predicted and measured. The IMC formation mechanism was revealed based on element distributions, the formation energy and the effective heat of formation of each IMC. The study would provide the basis for manufacturing crack-free and high-performance multi-material components in many applications in different industries.

Effects of Post-processing Heat Treatment on Tensile Properties and Strain Hardening Ability of Inconel718 Alloy Components Fabricated by Laser-Directed Energy Deposition

Effects of Post-processing Heat Treatment on Tensile Properties and Strain Hardening Ability of Inconel718 Alloy Components Fabricated by Laser-Directed Energy Deposition

Advancing sustainability in Electron and laser beam powder Bed Fusion technologies via Innovation: Insights from patent analysis

Additive manufacturing (AM) technologies continuously evolve in materials and operational processes. However, challenges related to energy consumption, material reuse efficiency, and the integration of Circular Economy (CE) principles may impede the overall sustainability of AM processes. As many industrial sectors adopt AM technologies, there is a growing need for innovative tools, methods, and frameworks that guide companies toward more sustainable and circular production practices. This shift involves improving resource efficiency and fostering new Circular Business Models that emphasize material recovery, product lifecycle extension, and waste minimization. This study assesses current and future trends in the development of sustainable AM technologies for processing metal feedstock, based on a comprehensive patent analysis covering the period from 2004 to 2024. We specifically focus on the sustainability impacts of Electron and Laser Beam Powder Bed Fusion (PBF-EB, PBF-LB) and Direct Energy Deposition (DED), given their widespread industrial applications. Patents were categorized into three groups: materials, processes, and components. Furthermore, AM technologies were analyzed according to their role within the production cycle: materials preparation, pre-processing, manufacturing, and post-processing. This categorization allows for a detailed understanding of how innovations in AM contribute to more sustainable production and consumption practices by improving energy efficiency, material usage, circularity, and overall environmental impact.

Mechanical properties and corrosion behavior of circular oscillating laser direct energy deposited nickel-based superalloy after different heat-treatment processes

Mechanical properties and corrosion behavior of circular oscillating laser direct energy deposited nickel-based superalloy after different heat-treatment processes

Grain structure control of TC11 alloy in laser direct energy deposition by a static magnetic field

This paper describes a novel in-situ adjustment method of static magnetic field (SMF) for laser additive manufacturing, which realizes the change of grain morphology and weave structure without changing the composition and performing post-processing. The TC11 alloy was prepared by laser direct energy deposition (LDED) under static SMF. The results show that a transverse static SMF of 0.5 T effectively suppresses the tendency of columnar crystals to grow continuously along the build direction and the dominant weaving direction of <0001> texture, and reduces the anisotropy of the TC11 alloy.

Effect of Inconel 625 coating via high-speed laser direct energy deposition on the fatigue characteristics of Q235 steel

Single-layer and double-layer Inconel 625 coatings were deposited on the Q235 steel using high-speed laser direct energy deposition (HL-DED). Steel grains in heat-affected zone (HAZ) coarsened due to the heat generated during the single-layer coating deposition. In contrast, double-layer coating specimens exhibited fine-grain regions in the HAZ due to repeated laser treatment reaching the solid-state phase transition temperature. Compared to bare Q235 steel, the yield and ultimate tensile strength of the single-layer coated specimens increased by 25% and 21%, respectively, while their elongation decreased by 32%. Tensile strength increased, while elongation decreased with the coating thickness. Although fatigue performance of bulk HL-DED Inconel 625 and as-deposited coating specimens was lower than bare Q235 steel, polished coated specimens exhibited better fatigue performance than bare Q235 steel. The coating thickness in the as-deposited condition had minimal impact on fatigue performance, but the fatigue performance of the polished coated specimens decreased with coating thickness. Corrosion fatigue life of the single-layer coated specimens in a 3.5% NaCl solution was three times better than bare Q235, and the fatigue life of double-layer coated specimens is not affected by the corrosive environment.

Cellular structure assisted enhanced deformation-induced martensitic transformation in laser-directed energy deposited ferrous medium-entropy alloy

The effect of cellular structure on the deformation behavior of laser-directed energy deposited Fe60(CoNi)30Cr10 medium-entropy alloys was comprehensively analyzed. High dislocation density and elemental segregation at cellular boundaries significantly promoted deformation-induced martensitic transformation and enhanced heterogeneous deformation-induced strengthening. This highlights the potential to optimize the mechanical performance of the alloy through cellular engineering.

Effects of wire feeding direction on the deposition characteristics of 316L stainless steel in laser-directed energy deposition

This study investigates the effect of wire feeding direction on the microstructure of 316 stainless steel during the laser-directed energy deposition (L-DED) process. The process parameters were optimised by varying the scan speed, laser power, and wire feed rate to identify a common parameter set for all feed directions to give desired weld bead geometries. The identified process parameter window has shown that the conduction mode is preferred over the balling and keyhole modes. Comprehensive microstructural characterization using optical and electron microscopy has revealed that for the same parameters, the front wire feed had higher penetration, while the back wire feed had a wider bead with optimal penetration. The current findings are of significance for advancing wire-L-DED additive manufacturing for more complex component designs.

Microstructure Evolution and Wear Behavior of Stellite12 Coating Prepared by Laser-Directed Energy Deposition on H13 Steel

Laser-directed energy deposition (LDED) was employed to apply a Stellite12 coating onto an H13 steel substrate. This study explored the effects of processing parameters on the dimensions of the deposited tracks. Comprehensive examinations were conducted on the coatings to assess their phase composition, microstructure, and wear resistance properties. The relationship between microstructural characteristics and thermal field was investigated through a synergy of numerical simulations and experimental analyses. The findings revealed that the Stellite12 coating displayed a heterogeneous microstructure with epitaxial growth and a slight texture across successive layers. The primary phase comprised a γ-Co solid solution and M23C6 carbides, contributing to a significant enhancement in hardness, which was observed to be 2.2 times higher than that of the substrate. The coating demonstrated superior performance in terms of lower friction coefficients and reduced wear rates at both room and elevated temperatures. The predominant wear mechanisms identified were oxidative wear. These results underscore the promising applications of Stellite12 coatings in industrial contexts facilitated by LDED technology.

3DCastleBenchy: a process-independent benchmark for additive manufacturing

Purpose The 3DCastleBenchy has been developed to facilitate wider adoption and use of additive manufacturing benchmarking artefacts which encourage both technical and non-technical users and designers to connect the growing number of technologies available. This tool will help people working with additive manufacturing to gain understanding of the limitations and design rules for each process. Design/methodology/approach Benchmarking is of critical importance for additive manufacturing, allowing for comparisons between technology capability, process optimisation and design guidelines. This work presents the 3DCastleBenchy, a design which balances aesthetic appeal and specific, measurable features which can be used for comparing various additive manufacturing processes. Findings The benchmark design was fabricated with three fundamentally different metal additive processes, laser-directed energy deposition (L-DED), laser powder bed fusion (L-PBF) and metal extrusion (MEX). These resulting parts were then analysed, thereby allowing common defects and limitations of each process to be identified, namely, the overhang limitations of traditional L-DED, the cracking that can occur in L-PBF and the deposition tool path artefacts present in MEX. Originality/value Existing benchmarks typically focus on either tolerance engineering features, or they are purely artistic/demonstrative pieces. The 3DCastleBenchy has been designed to find a balance between these objectives to facilitate communication of design for additive manufacturing concepts.

Effect of ZrB2 on microstructure and wear properties of TC4 alloy coatings by laser direct energy deposition

In this paper, ZrB2/TC4 alloy coatings with different contents of ZrB2 were prepared on the surface of TC4 titanium alloy using laser direct energy deposition technology. The effects of ZrB2 content on the microstructure, phase, microhardness and friction and wear behaviors of the TC4 coating were investigated, and the enhancement mechanism of ZrB2 on the coating properties was analyzed. The results show that with the increase of ZrB2 content, the coating successively produces the white ring-like structure of the first and the last, the parallel structure of the fishbone and the staggered structure of the TiB compounds, and the microstructure of the coating is transformed from the elongated grains to the fine grains. The microhardness and wear rate of the 15 wt% ZrB2/TC4 coating reached up to 352.1HV and 5.9 × 10−6 g/N•m, respectively. Compared with the 100%TC4 coating, the microhardness is increased by 14.6 % and the wear rate is decreased by 52.0 %, indicating that the addition of ZrB2 was beneficial to improve the friction and wear properties of coating. Interestingly, when the content of ZrB2 reached 20 %, the brittleness of the coating was too high, leading to the phenomenon of grooves on the wear surface of the coating, and the wear rate was reduced by only 45.5 %.

Microstructure and wear characteristics of austenitic stainless steel coatings fabricated through various directed energy deposition

Austenitic stainless steels are widely used in automotive and marine environments because of their high toughness, corrosion resistance, and wear resistance. The present comparative study focuses on the microstructure and wear resistance of double-layer austenitic stainless-steel coatings prepared on a ductile iron substrate using circular spot high-speed laser-directed energy deposition (DED) and broad-beam laser-DED. The results indicate that while the deposition process does not alter the physical phase of coating, it does influence the preferred orientation of surface grains. Both coatings exhibit characteristics of hypoeutectic alloys, where the harder eutectic structure serves as a skeleton to resist external pressure. The high-speed laser-DED coating demonstrates higher hardness and wears resistance due to its denser eutectic structure. In addition, its finer microstructure produces smaller wear debris, contributing to the formation of a denser oxide film, thereby enhancing wear resistance.

The Customized Heat Treatment for Enhancing the High-Temperature Durability of Laser-Directed Energy Deposition-Repaired Single-Crystal Superalloys.

The high-temperature durability performance plays a crucial role in the applications of single-crystal (SX) superalloys repaired by laser-directed energy deposition (L-DED). A specialized heat treatment process for L-DED-repaired SX superalloys was developed in this study. The effect of the newly customized heat treatment on the microstructure and high-temperature mechanical properties of DD32 SX superalloy repaired by L-DED was investigated. Results indicate that the repaired area of the newly customized heat treatment specimen still maintained a SX structure, the average size of the γ' phase was 236 nm, and the volume fraction was 69%. Obviously recrystallized grains were formed in the repair area of the standard heat treatment specimens, and carbide precipitated along the grain boundary. The size of the γ' phase was about 535 nm. The high-temperature durable life of the newly custom heat treatment specimen was about 19.09 h at 1000 °C/280 MPa, the fracture mode was microporous aggregation fracture, and the fracture location was in the repair area. The durable life of the standard heat treatment specimen was about 8.70 h, the fracture mode was cleavage fracture, and the fracture location was in the matrix area. The crack source of both specimens was interdendrite carbide.

Influence of cooling rate on microstructure, dislocation density, and associated hardness of laser direct energy deposited Inconel 718

This work deals with the effect of cooling rate on microstructure, dislocation density, and microhardness of laser direct energy deposited Inconel 718. Thermocycles were captured during direct energy deposition process using an infrared pyrometer. Cooling rate was estimated from the thermocycles at various laser powers and scanning speeds. In addition, a numerical model was developed to calculate cooling rate at different laser process parameters, and the same was verified with the experimental results. Microstructure and phases of the direct energy deposited Inconel 718 were observed using a scanning electron microscope and X-ray diffractometer, respectively. Top layer of the cladding was found to consist of fine equiaxed grains, whereas columnar dendrites were observed at the interface region of cladding layer and substrate. This is attributed to the variation in cooling rates between the top layer of the cladding and the interface region. γ, γ′, γ″ and Laves phases were identified to be the primary phases in the cladding layer. Moreover, niobium content was found to be high and varying with the cooling rate in the direct energy deposited Inconel 718. Dislocation density at varying scanning speed, i.e., cooling rate was estimated using the Williamson-Hall method. An increase in the dislocation density and concomitant improvement in the hardness was found with an increase in the cooling rate.

Influence of solid solution time on microstructure and precipitation strengthening of novel maraging steels

Effective subsequent heat treatment is crucial for achieving the desired microstructure and excellent mechanical properties in laser-deposited high-performance maraging steel. In this paper, we systematically investigate the synergistic relationship and tuning mechanism of different solution treatment times on the microstructure-property synergy of new maraging steels fabricated using laser direct energy deposition (LDED). To determine the optimal heat treatment process, solution treatment was conducted at 840 °C for varying durations, followed by aging at 530 °C for 2 h to induce precipitation strengthening. The results indicate that after 2 h of solution treatment, the alloy exhibits optimal ductility with an elongation of 7.90 % ± 0.15 %, attributed to the refinement of the martensitic matrix and precipitated phases, along with the formation of a small amount of residual austenite. When the solution treatment time is extended to 4 h, the alloy achieves its highest tensile strength, reaching 1958 ± 24 MPa. However, the elongation decreases to 7.31 % ± 0.12 % due to the coarsening of the martensite and secondary phase particles. After 6 h of solution treatment, significant coarsening and aggregation of the martensite and Fe2Mo intermetallic compounds markedly reduce the hardness, strength, and toughness of the alloy. By adjusting the solution treatment time, the size, morphology, and distribution of the martensitic matrix, Fe2Mo, and nanoscale precipitated phases play a critical role in the strengthening and fracture processes. Therefore, optimizing the precipitation behavior of the martensitic matrix and Fe2Mo intermetallic compounds through rational solution heat treatment is key to enhancing the mechanical properties of laser-deposited new maraging steels.

In-situ alloying of a Zr-based bulk metallic glass composite via powder-fed laser additive manufacturing and pure elemental blend

This study investigates the feasibility of synthesizing a ZrCuAlNb bulk metallic glass composite through in-situ alloying of pure elemental powder blend using powder-fed laser-directed energy deposition. The process parameters are carefully optimized and multiple laser remelting is applied to address the chemical inhomogeneity and elemental micro-segregation. A detailed microstructural examination confirms the successful discovery and development of an amorphous-crystalline composite structure.

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 sample 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.

Effect of ultra-fine grain zone on mechanical properties of CuCrZr-Hastelloy X bimetallic structure manufactured by laser-directed energy deposition

In this study, CuCrZr-Hastelloy X bimetallic structure featuring an ultra-fine grain zone (UFGZ) near the interface were fabricated by laser-directed energy deposition (L-DED). Samples with UFGZ were obtained with 300 °C preheating, whereas samples without preheating did not contain UFGZ. The microstructures and mechanical properties of samples with and without UFGZ were compared. The formation of UFGZ was attributed to the presence of a spherical phase near the interface, which was identified as Ni (Fe, Cr, Mo). Due to the higher melting point of Hastelloy X compared to CuCrZr, Ni elements mixed into CuCrZr with the flow of the molten pool, solidified first, and served as substrates for the heterogeneous nucleation, ultimately promoting the formation of UFGZ. With 300 °C preheating, the hardness of CuCrZr near the interface increased from 115.07 HV to 148.51 HV due to the presence of UFGZ. And the hardness gap near the interface decreased from 172.58 HV to 147.19 HV, which improved the uniformity of mechanical properties. Moreover, the nanoindentation tests results that UFGZ increased the hardness of the zone near the interface from 1.42 GPa to 1.72 GPa. Tensile test results indicated that the UFGZ altered the fracture mode from brittle to ductile. Samples with UFGZ exhibited ductile fracture, while those without UFGZ exhibited brittle fracture. At room temperature, the tensile strength of samples with UFGZ increased from 298.44 MPa to 347.05 MPa. For tests conducted at 400 °C, the tensile strength increased from 165.12 MPa to 229.53 MPa. This enhancement indicated that UFGZ could improve the strength and toughness of the interface, thereby enhancing the interfacial bonding strength. This study is of great significance for improving the interfacial bonding strength of CuCrZr-Hastelloy X bimetallic structures.

Study on Mitigation of Interfacial Intermetallic Compounds by Applying Alternating Magnetic Field in Laser-Directed Energy Deposition of Ti6Al4V/AA2024 Dissimilar Materials

Brittle intermetallic compounds (IMCs) at the interface of dissimilar materials can seriously affect the mechanical properties of the dissimilar components. Introducing external assisted fields in the fabrication of dissimilar components is a potential solution to this problem. In this study, an alternating magnetic field (AMF) was introduced for the first time in the additive manufacturing of Ti6Al4V/AA2024 dissimilar alloy components by laser-directed energy deposition (L-DED). The effect of the AMF on the interfacial IMCs’ distribution was studied. The results indicate that the contents of the IMCs were different for different magnetic flux densities and frequencies, and the lowest content was obtained with a magnetic flux density of 10 mT at a frequency of 40 Hz. When an appropriate AMF was applied, the IMC layer was no longer continuous at the interface, and the thickness was notably decreased. In addition, the influence of the AMF on the temperature distribution and fluid flow in the melt pool was analyzed through numerical simulation. The simulation results indicate that the effect of the AMF on the temperature of the melt pool was not significant, but it changed the flow pattern inside the melt pool. The two vortices inside the cross-section that formed when the AMF was applied caused different orientations of club-shaped IMCs inside the deposition layer. A sudden change in the streamline direction at the bottom of the longitudinal cross-section of the melt pool can affect the formation of the IMC layer at the interface of dissimilar materials, resulting in inconsistent thickness and even gaps. This work provides a useful guidance for regulating IMCs at dissimilar material interfaces.

Studies on hardness, elastic modulus and high temperature oxidation resistance of TiC and TiB2 dispersed titanium aluminide (Ti45Al5Nb0.5Si) composites developed by laser direct energy deposition

In this study, TiC (5 to 10wt.%) and TiB2 (5 to 10wt.%) reinforced TiAl (Ti45Al5Nb0.5Si) composites have been developed by laser direct energy deposition (LDED) process. The microstructures of TiAl/TiC and TiAl/TiB2 composites consist of TiC and TiB2 particles dispersed in γ and α2 matrix. The microhardness of the composites is improved from 571 HV to 634-683 HV (for TiC dispersion) and 649-694 HV (for TiB2 dispersion). The activation energy of cyclic oxidation is increased from 228kJ/mol (Ti45Al5Nb0.5Si) to 271-301kJ/mol (TiC dispersion) and 262-296kJ/mol (TiB2 additions). The mechanism of oxidation of the composites is established.