Laser Additive Manufacturing Technology Research Articles

A comparative study on the corrosion, wear, and tribocorrosion performances of Ti-6.5Al–2Zr–1Mo–1V (TA15) alloy fabricated by selective laser melting and laser metal deposition

Corrosion-erosion performances of Ti-6.5Al–2Zr–1Mo–1V (TA15) alloy fabricated by two laser additive manufacturing technologies, namely selective laser melting (SLM) and laser metal deposition (LMD) were investigated, and compared with those of traditional forged counterpart. Results show that SLM-ed TA15 possesses better corrosion, wear, and tribocorrosion resistances than LMD-ed and forged TA15. This is mainly attributed to the ultrafine-grain αʹ phase in the microstructure of SLM-ed sample, which improves the hardness and thereby enhances the wear and tribocorrosion resistance. Additionally, the complete αʹ phase formed in SLM-ed sample also avoids the galvanic corrosion that occurs at the α+β-type LMD-ed and forged samples.

Research progress in laser additive manufacturing of aluminum alloys: Microstructure, defect, and properties

Laser additive manufacturing (LAM) has attracted significant interest in developing Al alloys due to its potential to fabricate structural components at low cost and high efficiency. Nevertheless, LAM Al alloys still suffer many issues, including heterogeneous microstructure, various defects, and poor mechanical properties, significantly hindering the advancement of LAM Al alloys. This article seeks to provide a comprehensive overview of the current advancements made in the field of LAM Al alloys and attempts to establish an in-depth relationship between microstructural characteristics, defects, and performances. Development status and limitations of LAM technologies are described, microstructural characteristics of Al alloys in LAM are introduced, mechanisms of formed defects and corresponding mitigation measures are discussed, and current quality improvement strategies are summarized. Following the research of previous work, this review will provide an outlook on overcoming the existing challenges and provide a helpful resource and reference for the development of LAM Al alloys.

Microstructure and mechanical properties of Cu-Cr-Zr alloy prepared by electron beam additive manufacturing and laser-MIG hybrid welding

Cu-Cr-Zr alloys are widely used as medium-strength and high-conductivity copper alloys in aerospace, transportation and electronic information fields. The application of additive manufacturing technology is expected to realize the preparation of Cu-Cr-Zr alloy parts with complex structure and superior property. However, the commonly used laser additive manufacturing technology is not applicable to the preparation of copper alloys due to its intrinsic high reflection to laser. In this study, we adopted two technologies, i.e., electron beam additive manufacturing (EBAM) and laser-metal inert gas hybrid welding (laser-MIG), for the preparation of Cu-Cr-Zr alloys. Finite element simulation was employed to simulate the temperature field and residual stress field of the material during solidification. The microstructure, relative density, microhardness, tensile properties and electrical conductivity of the as-fabricated samples were characterized. The results showed that samples with better moldability were obtained by both methods at a line energy density of 600 J/mm. In the top area, both methods exhibit medium-sized equiaxed grains with more precipitated phases, showing the best comprehensive properties. The EBAM method demonstrates superior formability, better relative density and electrical conductivity due to more stable temperature field changes. On the other hand, the laser-MIG method obtains finer grains and higher mechanical properties because of a faster cooling rate, but leads to a decrease in relative density and electrical conductivity. This study presents new experimental data for Cu-Cr-Zr alloys prepared by EBAM and laser-MIG methods, contributing to extend the application of additive manufacturing in the preparation of Cu alloys.

Hybrid Laser Additive Manufacturing of Metals: A Review

Due to the unparalleled benefits of traditional processing techniques, additive manufacturing technology has experienced rapid development and continues to expand its applications. However, as industrial standards advance, the pressing needs for high precision, high performance, and high efficiency in the manufacturing sector have emerged as critical bottlenecks hindering the technology’s progress. Single-laser additive manufacturing methods are insufficient to meet these demands. This review presents a comprehensive exploration of metal hybrid laser additive manufacturing technology, encompassing various aspects, such as multi-process hybrid laser additive manufacturing, additive–subtractive hybrid manufacturing, multi-energy hybrid additive manufacturing, and multi-material hybrid additive manufacturing. Through a thorough examination of the principles of laser additive manufacturing technology and the concept of hybrid manufacturing, this paper investigates in depth the notable advantages of hybrid laser additive manufacturing technology. It provides valuable insights and recommendations to guide the development and research of innovative machining technologies.

Exceptionally strong and ductile bulk metallic glass composite with bioinspired architecture mimicking porcupine fish spine

Introducing soft crystalline phases into the glassy matrix to produce bulk metallic glass composites (BMGCs) is an effective way to enhance the ductility of bulk metallic glasses (BMGs). However, the introduction of soft crystalline phases severely sacrifices the strength, resulting in the strength-ductility trade-off. To defeat this dilemma, here, we successfully fabricate a bioinspired BMGC with architecture mimicking a porcupine fish spine. The bioinspired BMGC shows a pronounced yield strength of ∼800 MPa with an excellent fracture strain of ∼35 %. The fabrication of the bioinspired BMGC is achieved through infiltration and vitrification of molten Zr50Ti5Cu27Ni10Al8(Zr50) melt into the crystalline Nb skeleton fabricated by laser additive manufacturing (LAM). Such enhanced strength-ductility synergy is attributed to the asynchronous deformation associated with the delicate bioinspired heterogeneous architecture. The bioinspired structural design motif, enabled by the combination of LAM and infiltration casting technologies, opens a new window to develop high-performance BMGCs on a large scale for structural applications.

Enhancing tensile properties of laser additive manufactured FeCoNiCrMn high entropy alloy via adding Fe-based metallic glass

It has always been difficult to significantly improve the tensile strength of FeCoNiCrMn high entropy alloy (HEA) by traditional technical methods. Here, high-strength Fe-based metallic glass (MG) was precisely selected as the strengthening phase to reinforce the mechanical properties of FeCoNiCrMn HEA fabricated by laser additive manufacturing (LAM) technology. The results showed that although the addition of Fe-based MG with 5 wt% did not change the original phase composition of HEA, it facilitated grain refinement to a great extent. Of special significance was that the strength and ductility of HEA-MG exhibited a synergistic enhancement (σy, σUTS and εf were increased by 23.8 %, 28.4 % and 31.0 %, respectively) after Fe-based MG addition, deriving from the grain refinement, increased the dislocation density and formation of deformation twins.

Simultaneous improvement of strength and ductility of laser additively produced Ti6Al4V by adding tantalum

Laser additive manufacturing (LAM) technique can efficiently fabricate Ti6Al4V components of complex shapes, but often show poor mechanical properties. In this study, tantalum (Ta) was added into Ti6Al4V as an alloying element to improve the overall mechanical performance using a laser cladding system. It was found that Ti6Al4V–4Ta (corresponding to 4 wt% Ta) exhibited excellent mechanical performance with the yield stress of 956 MPa, ultimate tensile strength of 1042 MPa and the elongation of 10.8 %, meeting the ISO 7209 requirements for titanium and titanium alloys. The synergistic improvement of strength-ductility of Ti6Al4V–4Ta was attributed to the microstructure refinement, weakened α-variants selection, Ta solid solution, modified dislocation density and β phase content. Further quantitative analysis demonstrated that the strength increase was mainly contributed from the additional grain boundary, solid solution and dislocation induced by Ta elemental alloying. This study established Ta elemental alloying as an effective method to simultaneously enhance the strength and ductility of Ti6Al4V alloy using LAM technology.

Melt-grown behaviour of heat treated high-purity alumina ceramics prepared by laser directed energy deposition

Laser additive manufacturing technologies have attracted attention for the rapid preparation of melt-grown oxide ceramics, which are promising for high-temperature applications. However, the limitation of the mechanical properties and lack of understanding of high-temperature stability limit the applications of this type of material. In this study, the effect of heat treatment on melt-grown high-purity alumina ceramics prepared by laser-directed energy deposition (LDED) was investigated. The results show that melt-grown alumina ceramics have excellent high-temperature stability, as evidenced by the negligible changes in weight, geometric size, roughness, and phase composition after heat treatment. Compared with the same deposited material without heat treatment, the flexural strength of the heat-treated material is significantly increased, and the maximum strength can reach 547.85 ± 78.81 MPa, an increase of 102.96%. This increase in strength is attributed to crack healing during the heat treatment process. The heat treatment had less influence on the microhardness and fracture toughness. The results presented here can provide technical guidance for the fabrication of high-performance melt-grown high-purity oxide ceramics using LDED technology.

Microstructure and mechanical properties of Inconel 718 thin walls prepared by laser direct energy deposition and selective laser melting

This paper systematically investigates the microstructure, crystal structure and related mechanical properties of Inconel 718 thin walls prepared by two different methods, laser direct energy deposition (LDED) and selective laser melting (SLM), which are representative technologies for laser additive manufacturing of high-performance metal parts, and compares with conventional forged parts. The microstructure of SLM-part consists of columnar and equiaxed crystals with disordered growth directions, while LDED-part is mainly composed of coarse columnar crystals that grow perpendicular to the plane of the molten pool free surface. Unlike a strong 〈001〉 texture in the LDED-part, the SLM-part has a {110} texture in the XY plane, achieving stronger tensile strength due to different grain boundary strengthening and dislocation strengthening effects, which is found by comparing with LDED and forged Inconel 718 alloy. In addition, the difference in crystallographic texture between SLM and LDED-parts results in the different mechanical property anisotropy. The comparative study of two laser additive manufacturing technologies provides guidance for an in-depth understanding about the mechanism of laser additive manufacturing high-performance metal parts.

Enhancement of Microstructure and Mechanical Properties of High Nb-TiAl Alloys Prepared Using Laser Additive Manufacturing by Annealing Treatment

The microstructure, phase composition, hardness, and tensile properties of the Ti-48Al-2Cr-5Nb alloy have been systematically investigated using laser additive manufacturing technology. Results indicate that both the as-deposited and annealed microstructures contain both the α2 (Ti3Al) and γ (TiAl) phases. As the annealing temperature increased, the structure changed significantly from a large block structure to a fine equiaxed structure and finally to a large lamellar structure. Nevertheless, the amount and distribution of precipitation of α2 phase are obviously different, especially during the annealing at 1260 °C, where the fine α2 phases are evenly distributed on the γ phase matrix. The hardness value of the as-deposited sample is the highest, with a HV value of 484 at the room temperature, while the hardness value of the annealed sample at 1260 °C is the smallest, with a HV value of 344. An annealed sample at 1260 °C exhibits the highest tensile strength and elongation at room temperature, with values of 598 MPa and 2.1%, respectively. These values are increased by 1.15 times and 1.4 times compared to the as-deposited sample (519 MPa, 1.5%).

Assessment of self-lubricating coated cutting tools fabricated by laser additive manufacturing technology for friction-reduction

Dry cutting acting as a green machining technology is a promising manufacturing process in industrial applications; however, severe friction under dry cutting conditions aggravates tool wear and reduces tool life. Self-lubricating cutting tools exhibit excellent benefits in improving cutting properties and that can be used in sustainable machining. The complex process, low efficiency and thin coating thickness limit the production and use of present self-lubricating cutting tools with traditional methods. To enhance the lubricating effect and motivate the development of fabrication methods for self-lubricating cutting tools, Ni-based powders dispersed with MoS2 and Al2O3 particles were preset on the tool substrate; afterward, the self-lubricating coatings were deposited by laser powder-bed fusion additive manufacturing (AM) with a nanosecond fiber laser for cutting application. The self-lubricating coatings were characterized, and the friction and cutting performances of the AM self-lubricating coated tools (SLCs) were evaluated by sliding friction and dry machining tests. The results show that the developed SLC tools reduced the friction coefficient by 8.8–11.7%, cutting forces by 17.6–29.6%, and cutting power by 17.3–22.0% compared to conventional high-speed steel cutting tools (HSS). Built-up edge formation and tool wear were also significantly reduced. The observed mechanisms were attributed to the release of MoS2 particles from the coatings forming a lubricating film at the tool-chip interface, while the Al2O3 particles enhanced surface hardness. The results revealed the practicability of self-lubricating coated cutting tools fabricated by laser-based AM for friction-reduction, and that provide a cleaner process for dry cutting applications.

Influence of laser energy density on the microstructure and corrosion resistance of LPBF‐fabricated titanium‐based nanocomposites

AbstractAs a high‐efficiency laser additive manufacturing technology, laser powder bed fusion (LPBF) has unparalleled advantages in the manufacture of titanium matrix composites. In this work, the effect of laser energy density (LED) on the forming quality, microstructure evolution, and corrosion resistance of LPBF‐fabricated nanographene oxide reinforced titanium matrix nanocomposites (GO/TC4) was investigated. The results show that the optimal surface roughness and relative density of GO/TC4 nanocomposites fabricated by LPBF are 11.8 μm and 99.40%, respectively. The microstructure is mainly acicular α/α′‐Ti, accompanied by a small amount of β‐phase grain boundaries. When the LED is increased to 58.33 J/mm3, the self‐corrosion potential of GO/TC4 sample reaches 0.345 V in 3.5 wt% NaCl solution, and the GO/TC458.33 nanocomposite exhibits the highest corrosion resistance. The results revealed that the corrosion products on the surface of the samples were mainly composed of a passivation film of TiO2 and a small amount of Al2O3.

Microstructure and mechanical performance of laser additive manufacturing Ni50Ti40Cu10 and Ni45Ti40Cu15 alloy

Ni-Ti-Cu alloy can not only prevent scale and biological adhesion, but also has applications in aerospace, automotive engineering, and nanotechnology. In this study, Ni50Ti40Cu10 and Ni45Ti40Cu15 alloy large-size thin-walled parts are prepared on the surface of Ti plates using laser additive manufacturing technology. The optimum operational parameters are explored through a two-factor controlled variable method, based on which the effects of TiC and TiB2 addition on the forming quality of Ni50Ti40Cu10 and Ni45Ti40Cu15 alloys are further investigated. SEM, EDS, and other testing methods are used to determine the microstructure composition and distribution, and the composition of the physical phases of the alloy. Finally, tensile and hardness tests are carried out to study the mechanical properties of the alloy. The results show that the better operational parameters for laser additive manufacturing of large-size thin-walled Ni50Ti40Cu10 and Ni45Ti40Cu15 alloys are 1250w laser power and 300 mm min−1 scanning speed. 0.6 wt% TiC addition can achieve better forming quality of the large-size thin-walled parts. The large-size thin-walled Ni50Ti40Cu10 alloy precipitates significantly more Ti2Ni strengthening phases than the large-size thin-walled Ni45Ti40Cu15 alloy. Ni50Ti40Cu10 alloy large-size thin-walled parts have 20% higher tensile strength and 45.4% higher elongation compared to Ni45Ti40Cu15 alloy. The average hardness of Ni45Ti40Cu15 large-size thin-walled parts is 3.4% lower than that of Ni50Ti40Cu10 alloy.

Experimental study of mechanical properties of laser additively manufactured 316L stainless steels

Laser additive manufacturing (LAM), as an advanced additive manufacturing technology, has high efficiency and excellent precision in producing large size 3D printing elements. It has proven potential for application in buildings and civil infrastructure. However, in order to apply LAM technology to the production of components in civil engineering, it is necessary to understand comprehensively the mechanical properties of LAM products. In a previous study, the mechanical properties in the layer plane of LAM 316L stainless steels have been studied, but the mechanical properties in the building elevation plane are still unknown. To this end, an experimental study into the mechanical properties and microstructure of LAM 316L stainless steels has been undertaken and is reported in this paper. A total of 18 tensile coupons with two nominal thicknesses were extracted in various orientation angles relative to the print layer from the LAM prims for the uniaxial tensile tests. The influences of the orientation angle and thickness on the mechanical properties of LAM 316L stainless steels were investigated through the tensile tests. The test results show high anisotropy of the LAM 316L stainless steels in the building elevation plane, for which the anisotropy indexes of all mechanical properties exceed 10%, and the anisotropy indexes of the elastic modulus, Poisson's ratio and the proof stresses even exceed 25%. In addition, a very small Poisson's ratio value and an extreme short softening stage of stress–strain curves after peak values were identified for the coupons with the orientation angle θ = 45°. Microstructural characterisation of the LAM 316L stainless steels was also examined by means of optical microscopy and scanning electron microscope (SEM). The microstructure analyses observe an obvious layered structure perpendicular to the building direction and some columnar crystals perpendicular to the layer plane crossing the boundary, which might explain the reasons causing the high anisotropy of the macroscopic mechanical properties of LAM steels.

Semisolid-Liquid Fabrication of Cu–Cr Pseudobinary Alloy by Laser-Directed Energy Deposition

Copper–Chromium (Cu–Cr) pseudobinary alloys are promising materials for electrical application. Nevertheless, their fabrication remains limited by traditional techniques, which are not suitable for manufacturing homogeneous Cu–Cr alloys with uniformly distributed elements. Recently, semisolid-liquid manufacturing method has emerged as a promising technique route to fabricate Cu–Cr alloys. In this work, the laser-directed energy deposition (L-DED) as one of the laser additive manufacturing (LAM) technology, was successfully introduced for semisolid-liquid fabricating the homogeneous Cu–30 mass%Cr alloys. The obtained Cu–Cr alloys are constituted by fully melted Cu metallurgically combined with semisolid-liquid Cr. The close combination of Cu and Cr is benefit to improve the electrical conductivity of the alloy.

Microstructural evolution and performance improvement mechanism of Ti–6Al–4V fabricated by oscillating-wire laser additive manufacturing

This work proposes an oscillating wire laser additive manufacturing (O-WLAM), which is based on the wire laser additive manufacturing technology (WLAM) and combined with the laser oscillating welding technology. For different laser oscillation patterns, it shows a trend that metallurgical defects such as porosity, microstructural and columnar grain size decrease with the increase of oscillation frequency and oscillation amplitude. In solidified grains formed under laser oscillation, a complex oscillation of melt pool agitation could lead to a refining effect on the β grains size. The corresponding tendency of epitaxial growth of the prior β grains is weakened as well. The process experiments in this work provide a new idea of laser oscillation for wire laser additive manufacturing. The use of laser oscillation to achieve improvement of metallurgical defects and optimization of microstructure has some guiding significance for wire laser additive manufacturing.

High-temperature tribological properties of coatings repaired by laser additive manufacturing on railway wheel tread damage

Heavy-duty train wheels can easily cause local damage. Laser additive manufacturing technology has obvious advantages in repairing local damage to train wheels. The high temperature sliding condition caused by tread braking is a severe test for the coating of damaged wheels repaired by laser additive. In this study, three self-fluxing alloy powders, Fe-, Ni-, and Co-based, which are the most widely used in laser cladding, were selected as repair materials. The sliding friction wear performance at high temperatures was evaluated with an HT-1000 ball-disk wear tester, and the wear mechanisms of the repair area, substrate, and counterpart surfaces of the specimens were analyzed. The results show that the microstructure of the coating after the surface damage of the wheel is repaired by laser additive is mainly composed of dendritic structure and eutectic structure. Compared with the base material, the hardness of Fe-, Ni-, and Co-based alloy cladding coatings is significantly improved. At the same time, the wear resistance of the repaired wheel steel samples was improved to different degrees. The wear mechanism of the repaired area of the Fe-based alloy sample is mainly adhesive wear, and the wear mechanism of the repaired area of the Ni-based alloy sample is adhesive wear and oxidation wear. However, the surface of the wear scar of the Co-based alloy repaired sample is relatively smooth, the damage is slight, and the friction reduction effect is the best.

Research on Matching Strategy between Precision and Efficiency of Laser Melting Deposition of Metal Materials

At present, laser deposition forming technology of titanium alloy is widely used based on the flexibility of laser additive manufacturing technology. However, the mechanism and law of influence on the forming accuracy and efficiency need further study. Based on the orthogonal experiment, the analysis of the results shows that with the increase of energy density, the forming accuracy and efficiency are improved. There is a negative correlation between precision and efficiency. The experimental data are fitted and analyzed by establishing a statistical regression analysis model, a regression prediction model is established, and the regression prediction model is comprehensively calculated and analyzed, so as to optimize the appropriate parameter interval. During the forming process, the energy density is maintained in the range of 300 J/mm2–400 J/mm2, the forming accuracy is at a high level of 80%, the forming efficiency can be maintained in a high range of 0.35 g/s-0.40 g/s, and the whole forming process is in a state of high precision and high efficiency, so that the matching strategy of precision and efficiency in the forming process is the best. In order to improve the laser deposition forming titanium alloy.

Understanding the effect of low melting-point phases and homogenization annealing on the liquation cracks formation in the Al-Cu binary system during laser melting process

The alloy design is vital mission for eliminating the laser melting and additive manufacturing technologies defects. The low melting-point phases around the grain boundaries are considered as a source of the liquation cracks formation during laser melting process (LMP). In this work, a simple Al-Cu binary alloy with different Cu concentrations was selected as a model to understand the relation between low-melting point phases and liquation cracks formation during the LMP. In cast samples, most Al2Cu (θ phases) precipitate at the α-Al grain boundaries and during the LMP, the liquation cracks in the laser-melted zone (LMZ) initiated at the grain boundaries and propagated along the LMZ. Thus, homogenization annealing pre-laser melting at various times was done. The results showed that the cast Al-3.5Cu revealed high cracks susceptibility in the LMZ due to the presence of high amount of θ phases and during homogenization annealing the phases dissolved and the number of cracks significantly decreased. No cracks were formed in Al-7.5Cu at the cast and homogenized conditions due to the presence of many equilibrium eutectic θ phases, which heals the cracks (backfilling) during the solidification after the LMP. Liquation cracks susceptibility can be controlled by homogenization annealing.

Laser additive manufacturing of laminated bulk metallic glass composite with desired strength-ductility combination

Introducing ductile crystalline dendrites into a glassy matrix to produce bulk metallic glass composites (BMGCs) is an effective way to improve the poor ductility of bulk metallic glasses (BMGs). However, the presence of soft crystalline phases tends to decrease the strength and causes the strength-ductility tradeoff. Here, relying on the flexible laser additive manufacturing (LAM) technique that allows the composition tailoring of each layer, we successfully fabricate a lamellated Zr-based BMGC constructed by the alternating superimposition of soft and hard layers. The lamellated BMGC shows an exceptional combination of yield strength (∼1.2 GPa) and ductility (∼5%). Such enhanced strength-ductility synergy is attributed to the asynchronous deformation at two scales, i.e., inter-laminar and intra-laminar, and the unique dual-scale Ta particles that uniformly distribute on the amorphous matrix. The lamellated structure design motif, enabled by the flexible LAM technology, provides a new window for the development of high-performance BMGCs. It is also applicable to the synergistic enhancement of strength and plasticity of other brittle metallic materials.