Effect Of Laser Energy Density Research Articles

Effect of laser energy density on bead characteristics in wire-DED

Effect of laser energy density on bead characteristics in wire-DED

Effect of Laser Energy Density and Scanning Strategy on Residual Stress in Laser Melting Deposited FGH4096 Superalloy

Effect of Laser Energy Density and Scanning Strategy on Residual Stress in Laser Melting Deposited FGH4096 Superalloy

Effect of Laser Energy Density on Phase Evolution in Laser Surface Melted As-Cast Zr–Cu Alloy

Effect of Laser Energy Density on Phase Evolution in Laser Surface Melted As-Cast Zr–Cu Alloy

The deterministic effect of laser energy density on the microstructures of novel duplex stainless steel fabricated via in-situ alloying in laser powder bed fusion

Distinctive microstructures and distributions of novel duplex (ferrite δ + austenite γ) stainless steel can be fabricated using in-situ alloying of Fe–Cr–Mn alloy and pure Ni powders by tuning laser energy density in powder bed fusion. At low-level energy density (∼60 J/mm3), ferrite solidification dominates and results in bimodal ferrite of columnar and equiaxed grains. At medium energy density (∼100 J/mm3), fine acicular Widmanstätten austenite satisfying the Nishiyama-Wassermann orientation relationship was produced within the coarse grains of δ, which is the predominant phase although ferrite and austenite solidification occur. At high-level energy density (∼194 J/mm3), ferrite and austenite solidification occur and the resultant microstructure consists of nearly equivalent fine equiaxed-grained δ and γ. The key difference in the microstructure was attributed to the different melt pool overlapping and types, which can be characterized by the size and local ratio of Cr equivalent (Creq) and Ni equivalent (Nieq) values (Creq/Nieq). The melt pool characteristics fundamentally determine the local solidification and transformation mode at different energy densities. The testing results have shown that the novel duplex stainless steel possesses excellent mechanical properties compared to conventionally-manufactured counterparts.

Effect of laser energy density on the microstructure and properties of Tribaloy T-800 coating fabricated by laser cladding on the DZ125 alloy

Tribaloy T-800 coatings are fabricated on the DZ125 alloy by laser cladding, and the effect of laser energy density (η) on the macroscopic morphology, phase composition, microstructure, microhardness and the wear properties of the coatings is investigated. The experimental results indicate that cracks are observed in the coating fabricated with the laser energy density η1 = 33 J/mm2. However, as the laser energy density is raised to η2 = 50 J/mm2 and η3 = 75 J/mm2, the coatings become crack-free. The coatings consist mainly of face-centered cubic Co solid solution and Laves phase (Co3Mo2Si). The microstructure consists mainly of planar crystal, flower-like Laves phase, coarse Laves phase and lamellar eutectic structure. The average microhardness of the coatings is 717 HV0.5, 673 HV0.5 and 572 HV0.5 for laser energy densities of η1 = 33 J/mm2, η2 = 50 J/mm2 and η3 = 75 J/mm2, respectively. The wear mechanism of the coating fabricated with laser energy density η1 = 33 J/mm2 includes abrasive wear, fatigue wear and oxidative wear. However, as the η is increased to 50 J/mm2 and 75 J/mm2, the wear mechanism shifts to abrasive wear and oxidative wear.

Effect of Laser Energy Density on Amorphous Phase Content and Properties of Fe-Based Amorphous Coatings

Effect of Laser Energy Density on Amorphous Phase Content and Properties of Fe-Based Amorphous Coatings

Evaluation of antibacterial effect of a cationic porphyrin derivative on Pseudomonas aeruginosa in photodynamic therapy

BackgroundPseudomonas aeruginosa is a gram-negative bacterium without spores, and it is one of the pathogens that easily cause secondary infectious diseases when human immune function is low. The purpose of this study is to explore the inhibitory effect of photodynamic antibacterial chemotherapy-induced by cationic porphyrin derivative on clinical P. aeruginosa and its mechanism. MethodsThe uptake of photosensitizer by P. aeruginosa and L929 cells was measured by an ultraviolet spectrophotometer. Effect of laser energy density on the bacterial activity of P. aeruginosa and post antibiotic effect were measured by bacterial suspension and tenfold dilution method. Flow cytometry and scanning electron microscopy were used to observe the activity and morphological changes of P. aeruginosa after PACT treatment. ResultsThe uptake of Tetra-ATPP-Lys-by P. aeruginosa and L929 was shown as concentration-dependent and time-dependent. However the uptake of L929 cell had a clear difference with P. aeruginosa at the same time and concentration intervals(P < 0.05).The increasing laser energy density had a high inactivation effect of on P. aeruginosa at the same Tetra-ATPP-Lys-concentration(P < 0.05). Post-antibiotic effect of Tetra-ATPP-Lys -PACT was dose-dependent(P < 0.05). Bacterial viability which evaluated by the flow cytometry method demonstrated that the proportion of viable bacteria is decreased with the photosensitizer dose-dependent. The morphology and microstructure of P. aeruginosa after Tetra-ATPP-Lys -PACT was demonstrated by a scanning electron microscope(SEM). After PACT, the morphology of P. aeruginosa was rod-shaped, the outer membrane surface was rough, and the bacteria were dry flat, sunken, shrunk and deformed. ConclusionsCationic porphyrin photosensitizer had a great damage effect on P. aeruginosa under the PACT, which can effectively destroy the microstructure of bacteria and lead to bacterial inactivation and death.

Investigation of the effect of laser energy density on selective laser sintering of PA12 using a multi-physics field simulation method

Investigation of the effect of laser energy density on selective laser sintering of PA12 using a multi-physics field simulation method

Effect of synergistic cavitation erosion-corrosion on cavitation damage of CoCrFeNiMn high entropy alloy layer by laser cladding

The CoCrFeNiMn high entropy alloy (HEAs) clad layer was prepared on the surface of 304 stainless steel using coaxial powder feeding laser cladding. The effects of laser energy density on the macroscopic residual stress, crystallographic characteristics, microhardness, corrosion resistance and cavitation erosion (CE) resistance of HEAs clad layer were studied. With the decrease of laser energy density from 45 J/mm2 to 36 J/mm2, pore defects and abnormal coarsening of microstructure in HEAs cladding layer can be effectively avoided, the average grain size can be refined to 74.3 ± 1.7 μm, the average Schmidt factor is 0.43, which also shows the highest dynamic passivation tendency and corrosion resistance in artificial seawater. After 10 h-CE, the carrier density ND in the passivation film of HEAs clad layer can be as low as 3.24 ± 0.08 × 1022 cm−3, and the lowest mean depth erosion rates (MDER) is 0.68 ± 0.07 μm/h, which is much lower than that of 304 stainless steel substrate (4.23 ± 0.13 μm/h). The excellent CE resistance of the HEAs clad layer is attributed to the fact that its grains can effectively resist the plastic deformation and the surface passivation film can maintain a relatively high degree of integrity and continuous level after long aging CE, which has a considerable application prospect in marine engineering.

Effect of laser energy density on surface morphology, microstructure and mechanical behaviour of direct metal laser melted 17-4 PH stainless steel

Abstract The surface and microstructural characteristics of 3D printed parts play a significant role under mechanical loading. The authors have explored the effect of laser energy densities on the surface morphology, microstructure and mechanical behaviour of 17-4 precipitation hardened stainless steel fabricated under the direct metal laser melting technique. The considered processing parameters were laser energy density and its technical parameters: laser power, layer thickness, hatch spacing and scanning speed. The mechanical and metallurgical properties of the as-printed samples appeared better than the wrought counterpart due to the higher densification level (99.74 %) induced by the rotating scanning strategy. X‐ray diffraction revealed the presence of both the martensitic α phase and austenitic γ phase in the as-printed sample. There is no significant anisotropy in the mechanical behaviour as the build direction has a random texture with a fine columnar grain structure. The high laser energy density with low layer thickness results in an excellent surface finish. The tensile strength (1180 MPa) and the elongation for the as-printed sample (45.0 %) were considerably more significant than that for the wrought sample (1160 MPa and 26.0 %), which is attributed to the combination of low and high-angle boundaries, as confirmed by the electron backscatter diffraction results.

Effect of laser energy density on microstructure and properties Cu–Fe–P immiscible alloys fabricated by laser selective melting: heterogeneous and high strength and magnetic

Through the incorporation of phosphorus (P) as a third component, an in-situ formation of a magnetic phase with a nanotwin structure was achieved. The utilization of selective laser melting (SLM) enabled the synthesis of a Cu–Fe–P immiscible alloy that exhibits an integrated structure and function. The microstructure predominantly consists of a magnetic heterogeneous Fe–P-rich phase, comprising a mixture of Fe2P and a small quantity of Fe3P, which is distributed within the ε-Cu Cu-rich matrix in alternating “fiber-layer” and “particle-shape” forms. Additionally, the fibrous Fe2P phase exhibited precipitation of α-Fe, while the Fe–P-rich phase experienced the precipitation of high-density nanotwinned Cu (nt-Cu) particles. The microstructure density and structural characteristics of Cu–Fe–P immiscible alloys were enhanced through the adjustment of laser energy density, leading to improvements in their mechanical and magnetic properties. It was observed that the microstructure density initially increased and then decreased with increasing laser energy density. The highest relative density of the Cu–Fe–P immiscible alloy microstructure (98%) was achieved at a laser energy density of 53 J/mm3. Furthermore, the influence of laser energy density on the mechanical and soft magnetic properties of Cu–Fe–P immiscible alloys was examined. The findings indicate that the mechanical and soft magnetic properties of these alloys are affected by the laser energy density. The findings indicate that the compact Cu–Fe–P immiscible alloys exhibit favorable compression mechanical properties and soft magnetic properties. Specifically, the ultimate compressive stress can reach 890.5 ± 20 MPa, while the failure strain can reach 20.5 ± 2%. Additionally, the coercivity is observed to be as low as 20.0 Oe, the magnetic saturation strength as high as 93.5 emu/g, and the residual magnetization at 1.1 emu/g.

Effect of Laser Energy Density on Microstructure and Mechanical Properties of FeCrNi Medium Entropy Alloy

Effect of Laser Energy Density on Microstructure and Mechanical Properties of FeCrNi Medium Entropy Alloy

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 water erosion resistance of in situ synthesized (TiBx+TiC)/Ti composite coatings produced by laser cladding

(TiC + TiBx)/Ti composite coatings were prepared on a Ti6Al4V substrate by laser cladding to improve its microhardness and water erosion resistance. The 1 wt% Gr + 49 wt% Ni60 + 50 wt% Ti6Al4V composite powders were used as the precursor. The effects of laser energy density and powder deposition density on the geometric morphology, phase composition, microstructure, microhardness and water erosion resistance characteristics of the coatings were comprehensively studied through numerical simulation and experimental characterization. The results showed that the geometric morphology of the coating was determined by the laser energy density and powder deposition density; however, the microstructure of the coating was not completely understood. A high scanning speed was more conducive to grain refinement than a low scanning speed. In addition, the earlier precipitated hard phases provided heterogeneous nucleation sites for other grains and promoted their dispersion. Due to the dispersion strengthening and grain refinement effects of the in situ synthesized hard phases, the microhardness and water erosion resistance characteristics of the coatings significantly improved. With a laser energy density of 64 J mm−2 and a powder deposition density of 5 × 10−3 g mm−2, the microhardness of the coating reached 919.9 HV0.3, which was 2.8 times greater than that of the Ti6Al4V substrate. The water erosion resistance of the coating was the best.

Effects of laser energy density on morphology features and microstructures of the single molten track in selective laser melting

Single molten track (SMT) is the basic unit of the selective laser melting (SLM) process, of which the morphology features and microstructures have great significance on the molding quality. In this study, the effects of laser energy density (LED) on characteristics of SMT were studied with 316 L stainless steel processing by SLM. The results indicate that an optimized range of LED was between 200 and 500 J/mm3, which was the best for SLM process of 316 L leading to beautiful SMT appearance such as continuous uniform water-ridge-like surface, good contour straightness, smooth edges, little adhesive powder, and high densification. The microstructures of the SMT molten pool are mainly composed of equiaxed cellular and columnar dendrites. As the LED decreased, the cellular became smaller and disappeared, while the length and width of columnar crystals even gradually increased. The size of the cellular varies between 0.43 and 1.70 μm with the LEDs increase. The relationship between SMT characteristics and LED found in this work can be readily used to optimize SMT and control the microstructures in situ, and the laser energy density range that the work has identified will simplify most of the guess work in additive manufacturing.

Fabrication of high-performance copper circuits using laser-induced forward transfer with large receiving gaps based on beam modulation technology

Laser-induced forward transfer (LIFT) technology has been widely used to print 2D/3D structural patterns in the micron level of metals due to its contactless and maskless advantages. Still, it cannot meet the practical needs of the industry due to its drawbacks, such as low efficiency and a small receiving gap. This study proposes a new LIFT by modulating a Gaussian beam into an Arc beam using a liquid crystal on silicon spatial light modulator (LCOS-SLM) to achieve stable preparation of high-performance Cu circuits at large receiving gaps. First, the laser-induced monomer transfer modes of Gaussian beams and arc beams are studied. Then the effects of laser energy density, scanning velocity, and reception gap on the microcircuits prepared by Gaussian beam laser-induced forward transfer (GB-LIFT) and Arc beam laser-induced forward transfer (AB-LIFT) are studied systematically, and suitable process parameters are found. The transfer process of action of AB-LIFT is revealed. Under the optimized process parameters, the flight distance of AB-LIFT is up to 120 μm, which is about twice that of GB-LIFT, when the laser energy density is 1.94 μJ, and the scanning velocity is 3 mm/s. And the height of the microcircuit can be controlled by the number of depositions. It is demonstrated that the AB-LIFT can achieve stable transfer with large receiving gaps and efficiently prepare continuous Cu circuits with high bonding strength and low resistance. The minimum resistivity (7.46 μΩ∙cm) obtained by selecting optimized process parameters is about 4 times that of Cu bulk (1.76 μΩ∙cm). The application of the AB-LIFT method based on the beam modulation technique in microcircuit defect repair is verified.

Effect of absorption depth on chemical energy release from laser ablation of ADN-based liquid propellants

Ammonium dinitramide is a new green oxidant, which has been widely used in the field of liquid propulsion. In order to study the influence of doping laser absorber on the propulsion performance of liquid targets, the mixed solution of ammonium dinitramide and ionic liquid 1-allyl-3-methylimidazolium dicyandiamide was used as the ablation target, and the infrared dye was used as the laser absorber to change the doping content of infrared dye and laser energy density. The results show that the light absorption performance of liquid propellant is obviously improved with the increase of infrared dye content. The absorption coefficient and absorption depth of liquid propellant with infrared dye content of 0.6wt% are 425.19 cm−1 and 23.52 μm, respectively. The propellant with lower absorption depth produces high values of impulse bit, specific impulse, impulse coupling coefficient and ablation efficiency under the ablation of high laser energy density. The propellant sample doped with 0.6wt% infrared dye yielded the highest impulse bit of 114.32 μN·s, largest specific impulse of 84.14 s, highest impulse coupling coefficient of 1.07 mN·s·J−1, and the maximal ablation efficiency of 44% at the laser energy density of 21.51 J·cm−2. Furthermore, the effects of laser energy density and absorption depth on the chemical energy release of liquid propellant were studied. It was found that the maximum contribution of chemical energy to kinetic energy of ammonium dinitramide based liquid propellant is 93.93%. In general, improving the absorption performance of propellant can significantly enhance the energy release of energetic propellant. Which has guiding significance for propellant design and selection.

Surface Topography and Biocompatibility of cp–Ti Grade2 Fabricated by Laser‐Based Powder Bed Fusion: Influence of Printing Orientation and Surface Treatments

The selective laser melting process, commonly known as laser‐based powder bed fusion (LB‐PBF), enables the production of structures with unprecedented degrees of freedom that represents an excellent condition for development of metallic implants for biomedical applications. Herein, the effects of laser energy density on relative density and microstructure (presence of internal defects) of cp‐TiGd2 fabricated by LB‐PBF are studied. Additionally, the influence of printing orientation and different surface treatments on surface topography and biocompatibility are investigated. The aim of the research is to develop additive manufacturing process parameters that can achieve full density of cp‐TiGd2 with satisfactory biocompatibility, as a low‐cost alternative to biomedical materials such as Ti–6Al–4 V and Ti–6Al–7Nb. A wide range variation of process parameters leads to an optimized process with high density up to 99.97 ± 0.008%, improved surface roughness, and noncytotoxicity in horizontal and inclined as‐built condition, as well as in Al2O3 (blasting angle 0°) condition.

Improving the microstructure and mechanical properties of laser powder bed fusion-fabricated tantalum by high laser energy density

The effect of laser energy density on the microstructural evolution and the mechanical properties, including tensile property and nanoindentation creep behavior of Ta parts were investigated. A high laser power strategy (600 W) was used to obtain Ta part with high density. The microstructure of Ta fabricated with 200 W comprised columnar grains with strong 〈111〉 texture, while equiaxed grains with random orientation were found in Ta fabricated with 600 W. The elongation to failure of the specimen fabricated at 600 W was higher than that of the specimen fabricated at 200 W, which stemmed from pore elimination and equiaxed grains. Nanoindentation creep results showed that the movement of dislocations was the main creep mechanism and the influence of laser energy density was discussed.

A multiscale composite silicon carbide wick with excellent capillary performance

Wick is the key component of the heat pipe. Composite wick with multiscale porous structure has gained increasing interest for the high permeability and large capillary pressure. In this study, a grooved silicon carbide wick (GSCW) with a multiscale porous structure was fabricated via sintering and laser ablation. The resultant wick is composed of main grooves, the surrounding porous space formed by the stacking silicon carbide (SiC) particles, the microscale netted pores, and nanoscale pores on the groove walls. The effects of laser energy density on the surface morphology, wettability, capillary rise velocity, and overall capillary performance parameter of the GSCW are investigated. The presented wick is hydrophilic. The capillary rise velocity in the initial stage of GSCW was 7 times that of sintered SiC wick. The capillary performance parameter increased with the increasing laser energy density. The laser-ablated grooves improve the capillary performance parameter over 50 times. The rising performances of water, acetone, methanol, and ethanol were tested. The wick thickness has a significant effect on the capillary performance. The comparison of GSCW with other composite wicks in the literature reveals that it has very good capillary performance, making it an excellent wicking structure for heat pipe.