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Selective laser melting (SLM), an additive manufacturing technology, is expected to replace the traditional lost-wax casting process used in producing removable partial denture (RPD) frameworks. However, studies comparing the accuracy of RPD frameworks and the effects of process parameters are lacking.The purpose of this in vitro study was to optimize SLM process parameters and use a quantitative analysis method to improve the accuracy of 3D-printed RPD frameworks.The orientation and support structure of Kennedy Class II RPDs were designed in various ways by using 2 different software programs, CAMbridge and Magics. The optimum melt-pool parameters, including laser power, scan speed, hatch distance, and layer thickness, were determined empirically before manufacturing 12 RPD frameworks with 4 different process designs by using SLM (n=3). The accuracy of the RPD frameworks was determined by 3D scanning and comparing the 3D scan data with the original standard tessellation language (STL) RPD design with the best-fit algorithm of the Geomagic software program.Optimum melt-pool parameters were found with the function of density, surface roughness, and productivity (P=180 W, v=1200 mm/s, h=60 μm, t=30 μm). RPD frameworks fabricated by the optimized process parameters (167 ±105 μm) showed significantly better (P.05) mean ±standard deviation accuracy than the 3 other groups of RPD frameworks manufactured by using the nonoptimized process parameters (180 ±121 μm to 222 ±136 μm). The best accuracy was found with the transverse orientation and interconnected support structure.With the optimized design of process parameters, clinically acceptable RPD frameworks were produced. The accuracy of RPD frameworks fabricated by using SLM varied according to the design of the process parameters, indicating that SLM technology can replace the traditional lost-wax casting process.

Exploiting energy-saving potentials while obtaining ideal processing results is highly sought for in fiber laser welding (FLW) applications. However, little is known about the correlation between energy consumption and bead geometry of FLW, which is largely determined by processing parameters. In this study, to find the optimal processing parameters of FLW, an ensemble of variable neighborhood search-based gene expression programming (VNS-GEP) and black-box metamodels (EGBM) is presented, combined with non-dominated sorting genetic algorithm (NSGA-II) to form the proposed optimization methodology. Firstly, the optimal weight coefficients of VNS-GEP and two black-box metamodels (Kriging and SVR) are determined considering the leave-one-out generalized mean square error. Then, the EGBM is used to establish the relationship between processing parameters (laser power, welding speed and defocus distance) and response results (energy consumption and bead geometry). Additional experiments are then performed to validate the accuracy of EGBM. Analysis of variance (ANOVA) is carried out to study the main effects of the processing parameters on response results. After that, NSGA-II is employed based on EGBM to approximate the Pareto front of processing parameters with minimal total energy consumption (TEC) and maximal depth-to-width ratio (DWR). Finally, experimental validations show that the obtained solutions can achieve ideal DWR and significant reductions in TEC. In conclusion, the proposed hybrid methodology, EGBM-NSGA-II, can facilitate obtaining optimal welding processing parameters and provide a reliable empirical basis for low-energy laser manufacturing.

The laser welding (LW) process of highly reflective materials presents low thermal efficiency and poor stability. To solve the problem, the effects of subatmospheric environment on LW process, technological parameters in subatmospheric environment on weld formation and welding with sinusoidal modulation of laser power on the stability of LW process in subatmospheric environment were explored. The AZ31 magnesium (Mg) alloy was used as the test materials. The test result revealed that the weld penetration in subatmospheric environment can increase by more than ten times compared with that under normal pressure. After the keyhole depth greatly rises, significantly periodic local bulge is observed on the backwall surface of the keyhole and the position of the bulge shifts along the direction of the keyhole depth. Eventually, the hump-shaped surface morphology of the welded seam is formed; moreover, the weld width in local zones in the lower part of the welded seam remarkably grows. During LW in subatmospheric environment, the weld penetration can be further greatly increased through power modulation. Besides, power modulation can inhibit the occurrence of bulges in local zones on the backwall of the keyhole during LW in subatmospheric environment, thus further curbing the significant growth of the weld widths of hump-shaped welding beads and local zones in the lower part of welded seams. Finally, the mechanism of synchronously improving the thermal efficiency and stability of LW process of highly reflective materials through power modulation in subatmospheric environment was illustrated. This was conducted according to theoretical analysis of recoil pressure and observation results of dynamic behaviors of laser induced plasma clouds and keyholes in the molten pool through high speed photography.

Laser powder bed fusion (LPBF) is a promising technology that requires further work to improve productivity to be adopted more widely. One possible approach is to increase the laser power and scan ...

We report laser cladding of pure titanium on a CoCrMo alloy using directed energy deposition. Using electron microscopy, the microstructural evolution upon varying the process parameters, especially laser power and powder feed rate, was investigated in relation with crack formation. Cladding layers showing dilution rates of more than 5% contained cracks due to the formation of the brittle Co2Ti intermetallic phase. The observed cracks could be ascribed to a mismatch in thermal expansion and a resulting stress of more than 440 MPa acting on the Co2Ti phase, as determined by density functional theory and nanoindentation. Furthermore, an excess laser energy caused chemical inhomogeneity and unmelted Ti powder particles, while a deficient laser energy resulted in lack of fusion. Neither cracks nor partially melted powders were observed for a powder feed rate of 3 g/min and a laser power of 225-300 W, for which the dilution rate was minimized to less than 5%. For such samples the cladding layers comprised pure α-Ti and a uniform CoTi interface with Co2Ti islands.

The high corrosion resistance, low density, and useful biological activity with heat resistance of titanium alloys have made them the most outstanding choice in various industrial applications. However, their poor tribological properties inhibit utilizing them in applications that need abrasive and adhesive wear resistance. Laser cladding is being applied to increase the capabilities of such alloys by allowing the deposition of different hard coating materials. This paper attempts to study the thermal, microstructure, and clad layer geometry evolution during coaxial laser cladding of Ti6Al4V titanium alloy with tungsten carbide + nickel-based alloy preblended powder. Owing to the difficulty in experimentally measuring the thermal and microstructure evolution due to lots of laser processing parameters, a new three-dimensional numerical model based on finite-difference analysis for studying the entire process has been proposed. The behavior of the different thermophysical properties of WC, NiCrBSiC, and Ti6Al4V materials, as well as the phase transition based on latent heat and fluid dynamics considering materials velocity, viscosity, and buoyancy force, during melting and resolidification processes, were considered to improve and ensure the accuracy of the numerical model. The proposed model could be applied to accurately estimate the temperature history and the deposited clad layer morphology and geometry. The cooling rate and thermal gradient were investigated to predict the solidification rate and microstructure by using different laser cladding parameters. It was confirmed that the laser power has a substantial impact on the peak temperature in the melt-pool, while the laser scanning speed has a significant effect on the heating and cooling rates. In conclusion, the process parameters have to be carefully chosen to certify a good quality clad layer with the preservation of the WC particles.

We firstly propose the integration of heterogeneous Tm:YAG and Ho:YAP crystals into a single bulk structure for a compact, diode-pumped passively Q-switched (PQS) Ho laser. Efficient 2129 nm laser, with maximum CW power of 6.67 W was obtained from the Tm:YAG/Ho:YAP gain medium, with slope efficiency of 38.3% and optical conversion efficiency of 27.4% by considering the incident diode power at 785 nm. Modulated by a Cr:ZnSe saturable absorber inside a hybrid cavity, characteristic self-pulsing of the integrated Ho laser can be suppressed for a stable PQS process, where average output power of 743 mW at 2053.3 nm was obtained with shortest pulse duration of 123 ns at 14.2 kHz. As the maximum thermal stress of 48.2 MPa is far below the fracture limits of each integrated section (~160 MPa), higher laser power can be expected. The results pave the way to explore the integration of other existing Tm-doped and Ho-doped hosts for an accessible 2.1 m source.

In this study, we investigate the influence of in situ reactive synthesis of Ti6Al4V- AlCoCrFeNiCu high entropy alloys by laser metal deposition on the microstructural and mechanical properties of the as-built alloy as opposed to the traditional method of mixing powders via a ball mill prone to contamination and segregation. We explore the capability of a new alloy design by combining two base alloys via in situ reactive alloying, delivering the Ti6Al4V and AlCoCrFeNiCu high entropy alloy powders from multiple powder feeders and regulating their feed rate ratios. The nano mechanical, tribological and microstructural morphologies of the alloys were characterized using a nanoindentation tester, a tribometer, XRD and SEM, respectively. The results showed that satelliting the high entropy alloys powder and the Ti6Al4V powder fraction using double powder feedstock had a homogeneous distribution with dendritic structures. Optimization was achieved at a laser power of 1600 W, a scan speed of 12 mm/s and a powder flow rate of 2 g/min. The surface roughness (Ra) for Ti-6Al-4V, AlCoCrCuFeNi and (Ti-6Al-4V)-(AlCoCrCuFeNi) alloy was 0.5 μm, 0.63 μm and 0.80 μm, respectively. The high wear resistance of the novel Ti6Al4V- AlCoCrFeNiCu alloy was influenced by the hardness of the alloy which was higher than the Ti6Al4V alloy and the AlCoCrFeNiCu alloy. This study successfully defines the capabilities of in situ fabrication of high entropy alloys and presents novel techniques for multiple powder preparation of high entropy alloys using laser additive manufacturing, to permit the next generation of compositionally graded materials for aerospace components.

In this paper, 50 vol% TiCp/Ti6Al4V composites without pores, cracks or poor fusion were fabricated by laser melting deposition (LMD) technology using 500 W laser power (lower power, LP) and 1000 W laser power (higher power, HP). The microstructure of different deposited layers was analyzed and the corresponding microhardness was measured. The results show that the composites are composed of undissolved TiC, in-situ TiC (eutectic TiC and primary TiC), α Ti and β Ti. It is interesting that the microstructure from the bottom layer to the top layer presents a graded distribution when all layers have the same composition. The eutectic TiC is mainly formed in lower layers while the primary TiC is mainly in upper layers. With increasing layer number, the size and number of the primary TiC grains increase and the primary TiC grows gradually from granules into dendrites, however, the number of the undissolved TiC particles decreases along the depositing direction. The simulation results show that the peak temperature of deposited layer increases while the cooling rate decreases with increasing layer number. Different thermal history affects the diffusion of carbon and the evolution of TiC, and then affects the microstructure distribution of the composites. This graded microstructure leads to the graded distribution of microhardness. The microhardness of the LP composite rises from 432.5 HV to 488.1 HV, while the HP composite rises from 435.5 HV to 604.3 HV from the bottom layer to the top layer, respectively.

The effects of irradiation time (IT), laser power (LP), and spot diameter (SD) on the damage caused to quartz ceramics under continuous-wave laser irradiation were investigated through an orthogonal experiment. The experimental results show that the LP has the dominant effect on the depth of an ablation pit, while the SD has the greatest impact on the diameter of the ablation centre. The diameter and depth of the ablation pit were both positively correlated to the irradiation energy. The bubbles and molten silica transition layer affected the laser beam's reflection and transmission properties, leading to the incident laser beam scattering into the entire ablation pit and forming an elliptical ablation pit. Furthermore, a 3D finite element (FE) model considering a dynamic heat source was developed to simulate the laser damage process. The shape and dimension of the ablation pit predicted by the FE model were consistent with those obtained through the experiment, demonstrating the effectiveness and rationality of the model. The FE analysis results show that the different ablation rates in the radial and depth directions significantly influence the morphology of the ablation pits. The temperature gradient in the transition region increases while the thickness of the transition region decreases as the LP increases. This indicates that a large LP will lead to greater thermal stress in this area and result in more microcracks.

Additive manufacturing (AM) is a type of manufacturing technologies whereby the material is added a layer upon layer to produce a 3D object. Produced 3D parts are applied in such industry sectors as space, aviation, automotive, building and has excellent future promises. These days, the commercially promised technique for metal manufacturing are laser metal deposition (LMD), direct metal laser sintering (DMLS). Our study concentrated on the investigation of mechanical properties of 17-4 PH stainless-steel parts produced by laser sintering. The effect of the laser sintering process parameters (laser power, scanning speed and energy density) on the ultimate stress, yield stress and Young’s modulus was determined. We showed an evolution of the microstructure. The detected defects were classified. This study allowed to determine optimal process parameters for laser sintering of SS 17-4 PH and to describe mechanical properties of the produced parts as well as helped to show future possibilities of the development of laser sintering technology.

The microstructure, phase composition, texture, and tensile properties of Ti48Al2Cr2Nb5Ta alloy prepared by laser additive manufacturing (LAM) were all investigated in detail. The microstructure of the alloy is constituted of α2(Ti3Al), γ(TiAl), and β/B2 (β ordered to B2) phases, according to the results. The microstructure changes from lamellar structure to lamellar structure divided by massive β/B2 phase when the laser power increases from 1.0 kW to 2.2 kW. Furthermore, when the laser power is 2.2 kW, the content of the β/B2 phase achieves its highest value (9.43%), whereas when the laser power is 1.8 kW, the content of the α2 phase reaches its maximum value (9.43%). The crystal texture of the γ(111) and α2(0001) orientations strengthens as laser power increases. Tensile characteristics demonstrate that the 1.4 kW alloy has the best tensile strength and elongation at room temperature and 750 °C, with values of 677 MPa, 651 MPa, and 1.8%, 2.2%, respectively. However, when compared to other alloys, the 1.4 kW alloy's tensile strength and elongation at 850 °C are slightly lower (538 MPa 13%).

The AA7075 aluminum alloy with Ti6Al4V titanium alloy in lap configuration was successfully joined with laser fusion brazing method without filler wire. The effects of laser fusion brazing parameters, including defocus distance and laser power, on the joint appearance, interfacial microstructure and mechanical properties of the joints were explored. The results indicated that a good joint appearance could be obtained with variation of defocus distances. The adjustable range of laser power was expanded with the increase of defocus distance, from the range of 1600-1800 W with the laser spot diameter of 1.0 mm (defocus distance of +10 mm) to 2600 W–3400 W with the laser spot diameter of 2.7 mm (defocus distance of +20 mm). It was observed that the wettability of molten aluminum alloy on titanium alloy was improved with the increase of laser power, the wetting length was increased from 1.76 mm to 3.62 mm and the contact angle was decreased from 32.8° to 21.6° upon increasing the total laser power from 2400 W to 3000 W with the defocus distance of +15 mm. There was a continuous 0.7 ± 0.2 μm thick TiAl3 IMC (intermetallic compound) layer at the brazing interface with the defocus distance of +15 mm and laser power of 3000 W. The tensile strength and fracture location of the joints were mainly dependent on the spreadability and IMC thickness along the interface. Poor spreadability and too thick IMC thickness at the inner part of interface will result in fracture along the Al/Ti interface and lower strength. The best mechanical properties of the joints with the fracture load of 3621 N on average could be obtained with the defocus distance of +20 mm and laser power of 3400 W.

In this research work, the effect of laser cutting parameters on material removal rate of aluminium 5052 is presented. The material removal rate has been analysed using various investigating techniques such as precise measuring scale and optical microscope. The various cutting parameters considered such as cutting speed, laser output power, nozzle stand-off distance and nozzle diameter. The cut quality further investigated for kerf width deviation and surface roughness using one factor approach. Using microstructural analysis, it was analysed that cutting rate and laser power as most significant parameters.

Ti6Al4V is one of the most widely used titanium alloys due to its excellent mechanical, physical, and chemical properties. Laser surface texturing is a promising method to endow new functions of material surfaces; however, direct generation of laser-induced periodic surface structure (LIPSS) on the Ti6Al4V surface by nanosecond laser is rarely reported. In this study, by nanosecond laser irradiation in nitrogen atmosphere, the ripples (a typical LIPSS) were directly fabricated on the Ti6Al4V surface. By single-line laser scanning, the effects of laser irradiation parameters including the laser power and repetition frequency on the formation and evolution of the ripples were systematically investigated, followed by optimizing the laser irradiation parameters to achieve the large-area regular and clear ripples with relatively good surface quality as well. Furthermore, by performing contrast experiments in argon atmosphere, the role of nitrogen atmosphere on the formation of ripples was confirmed. Accordingly, formation mechanism of the ripples was discussed. Finally, the effects of the formed ripples on the surface color and wettability were preliminarily characterized to demonstrate the potential applications of surface ripples. This paper provides a nitrogen assisted method to fabricate large-area ripples on the Ti6Al4V surface by nanosecond laser irradiation.

Additive manufacturing is a highly projected technology that continues to evolve and improve. In this context, laser-based powder bed fusion (L-PBF) offers a series of advantages for manufacturing parts of high geometric complexity, impossible or too costly to process through conventional processes. However, anticipating the effect of processing parameters on the resulting microstructure remains challenging due to the complexity of the involved processes. In this sense, numerical simulation, also substantially improved in the recent decade, in particular finite element analysis, offers considerable precision, comparable to results obtained by experimentation. Therefore, in this work, the applicability of numerical simulation is evaluated to predict the effect of laser power, scanning speed, and hatch spacing on the dimensions of the molten pool, degree of porosity, and the resulting microstructure. Ansys Additive package was employed to simulate a single bed deposit, evaluate the porosity, and determine the microstructure of the 316L stainless steel processed through L-PBF. The results indicate that the lowest degree of porosity is obtained with high laser power, low scanning speed, and the lowest hatch spacing with a recommendable volumetric energy density greater than 60 J/mm3. Through the simulation of the microstructure, it was possible to obtain information on the thermal gradient, solidification rate, and melt pool characteristics. Ansys Additive proves a powerful tool to understand microstructure evolution and furthering customization of mechanical properties.

Pores are some of the most common defects that form during direct laser deposition of ceramic materials. A mathematical model of pore formation for Al2O3-ZrO2 ceramic was developed. The pore formation model, which was developed from the bubble escape factor, reveals the relationship between the movement of the solid-liquid interface of the molten pool and that of the bubbles. In the frontier region of the molten pool, with increasing laser power, the proportion of bubbles that escaped and the area from which bubbles escaped increased. With increasing laser power, the actual and theoretical porosity decreased from 80 % to 40 %. At the central region of the molten pool, the bubble escape factor increased with increasing bubble diameter under the same laser power. The theoretical porosity and the actual porosity decreased with increasing laser power. The pore formation model provides a basis for fabricating high-quality Al2O3-ZrO2 ceramics by direct laser deposition.

The process of marking the surface by laser provides advantages for applications in many fields due to its high processing speed, non-contact precision marking at constant quality with minimal human intervention. The produced laser marked objects are used for product identification and traceability and also to prevent illegal copying of products. In this regard, mark readability seems to be one of the factors responsible to produce good quality marks. The application of process parameters such as laser power, scanning speed and pulse frequency had a significant role for marking engineering materials surface for qualities and characteristics. The paper focused to generate good quality square shaped marked surface in a minimal possible time on the surface of stainless steel 304 using multi diode pumped fiber laser marking system. The studies provides the process parameters influence on marking characteristics for a single pass laser marked surface. Experimental results revealed that the application of process parameters such as laser power of 15 W, pulse frequency of 50 kHz, scanning speed of 35 mm/s and duty cycle of 99% produces better squared shaped marks on stainless steel 304.

In the Rapid Prototyping process, surface finish is very critical as it affects the part quality. As Rapid Prototyping is moving towards Rapid manufacturing there is an increasing stress on obtaining good quality parts. Surface finish of Rapid Prototyping parts is becoming more and more important with more parts being used for end purposes. Good surface finish is required for better functionality and look, but also for cost reduction in terms of reducing post-processing expenditure. A critical study and analysis of process parameters behaviour has been carried out for assessing the surface quality of parts manufactured on Selective Laser Sintering Rapid Prototyping system. The principal concern of experimental work has been investigated for achieving better surface finish by which the life of parts is governed. The primary objective of study is to analyze the optimum process parameters of Selective Laser Sintering Rapid Prototyping system. The material selected for study is “Dura Form“ and experimental work was carried out on selective laser sintering rapid prototyping machine DTM Vanguard 2500. Taguchi method is used to investigate the parameters and results are improved by using signal-to-noise methods. The major process parameters selected for study were Part Orientation, Laser Power and Scan Spacing. The study and analysis depict that Part Orientation has a major effect on the surface roughness of the part produced on Rapid Prototyping Machine. It has been observed from the study that lower value of Part Orientation level I (0 degree) gives better finish and this is because of less number of layers required for manufacturing of part. It has been observed from the study of second process parameter i.e. Laser Power that the surface finish was better at 16 W. Similarly, the surface finish obtained at lower values of Scan Spacing was for better as compared to higher values of Scan Spacing. The comparative analysis of three-process parameter indicates that the effects of variation of Part Orientation and Scan Spacing parameters are more as compare to Laser Power.

Purpose The purpose of this study is to investigate the microstructural evolution of high-strength 2024 Al alloy prepared by the laser powder bed fusion (L-PBF) additive manufacturing (AM) route. The high-strength wrought Al alloy has typically been unsuitable for AM due to its particular solidification characteristics such as hot cracking, porosity and columnar grain growth. Design/methodology/approach In this research work, samples were fabricated using L-PBF under various laser energy densities by varying laser power and scan speed. The microstructural features that developed during the solidification are correlated with operating laser parameters. In addition, finite element modelling (FEM) was performed to understand the experimentally observed results. Findings Microstructure evolution and defect formation have been assessed, quantified and correlated with operating laser parameters. Thermal behaviour of samples was predicted using FEM to support experimental observations. An optimised combination of intermediate laser power and scan speed produced the least defects. Higher energy density increased hot tearing along the columnar grain boundaries, while lower energy density promoted void formation. From the quantitative results, it is evident that with increasing energy density, both the top surface and side wall roughness initially reduced till a minimum and then increased. Hardness and compressive strength were found to decrease with increasing power density due to stress relaxation from hot tearing. Originality/value This research work examined how L-PBF processing conditions influence the microstructure, defects, surface roughness and mechanical properties. The results indicates that complete elimination of solidification cracks can be only achieved by combining process optimisation and possible grain refining strategies.

Low noise synchronization of the frequency and phase of a DFB fiber laser and two fiber ring cavities was achieved based on a two-channel optical injection lock and phase lock loop. Two-channel modulation signals of different frequencies were adopted to extract the phase noise signals of the two fiber ring cavities. Finally, the lasers from the two fiber ring cavities were coherently combined in the closed loop of the control system owing to the synchronous frequency and phase. The power stability and polarization stability of the combined laser was improved under the optical injection lock and phase lock loop. The phase noise of the two cavities was $6.56 \times 10^{-7}$ rad/Hz1/2 and $1.34 \times 10^{-6}$ rad/Hz1/2 at 10 Hz; and $7.77 \times 10^{-8}$ rad/Hz1/2 and $1.35 \times 10^{-7}$ rad/Hz1/2 at 10 kHz. The total combined power was ~580 mW in the closed loop, and the entire system oscillated under a single frequency, providing excellent power scaling ability.

The emerging technique of carbonization of polyimide (PI) by direct laser writing receives great attention for its flexibility, versatility, and ease-of-patterning capability in creating a variety of functional laser-induced graphene (LIG) sensors and devices. LIG prepared by CO2 laser irradiating of the PI film is characterized by scanning electron microscopy, X-ray diffraction (XRD), transmission electron microscope (TEM), specific surface area analyzer, synchronous thermal analysis, and Raman spectroscopy with the focus on investigating the effects of laser parameters (e.g. power, scanning speed) on the microstructure, thickness, and sheet resistance of LIG. Both TEM and XRD indicate that LIG is composed of many graphene layers with a layer spacing of 0.34 nm. The specific surface area of LIG decreases with the increase of laser power. The ratio of the thickness of LIG over the depth of the carbonized PI film as the expansion ratio characterizes the expansibility of LIG. The influence of laser scanning speed and off-focus value on the sheet resistance of LIG is explained by the superposition mechanism of laser scanning spots.

3D printing (3DP) of polymers using fused filament fabrication (FFF) is not yet massively adopted in industrial environments due to shape accuracy and surface integrity limitations. However, the FFF process combined with laser processing (hybrid manufacturing) or other precision machining processes is under investigation nowadays and is a promising combination for high quality 3DP final parts. This work investigates the effects on the dimensional accuracy and the surface roughness of process parameters, during low power CO2 laser cutting (LC) of thin acrylonitrile butadiene styrene (ABS) plates manufactured with the FFF process. Even though LC is highly flexible and the quality of the machined surfaces is versatile, certain problems are associated with LC, such as the kerf angle formation and the surface texture quality, which need optimization in respect to the LC parameters. The full factorial design methodology is adopted, having four parameters as input, i.e., stand-off distance (SoD), raster deposition angle (RDA), laser speed (LS), and laser power (LP), and kerf geometry characteristics as output, i.e., kerf widths (upper, middle, and down; Wu, Wm, and Wd), kerf angle (KA), and average and max height surface roughness (Ra and Rt). The statistical analysis is used to investigate the relations between the input and the output parameters. Seventy-two independent experiments were utilized. The analysis of variances (ANOVA), the interaction study, and the quadratic regression models (QRM) were adapted to fit the input with the output parameters, optimize the process KA close to 0°, and minimize the Ra close to 0 μm. The optimum parameter values (7.5 mm SoD, zero RDA, 14.4 mm/s LS, and 105 W LP) are validated by seven independent experiments, which show that only the Wu and Ra predicted values are close to the actual values following the ANOVA analysis and the mean average percengtage error (MAPE) index.

BACKGROUND: A class of additive manufacturing technologies called Laser powder bed fusion (LPBF), which allows fabricating metallic components with complex geometries in near-net-shape, can be employed for fabricating patient-customized orthopaedic implants. Selection and optimization of the LPBF process parameters are critical to achieving the required biomechanical properties and fabricability of such implants. METHODS: The process parameters of direct metal laser sintering, the most widely used LPBF process, were optimized for fabricating Ti6Al4V ELI orthopaedic implants, based on ASTM and ASM standards. The parameters included Laser power, Laser velocity and hatch distance, which were varied using Taguchi approach. A multi-criteria decision-making technique (TOPSIS) was employed to optimize the process parameters considering yield and ultimate tensile strength, percentage elongation, part density, volumetric energy density and printing time. In-vitro cytotoxicity and in-vivo muscle implantation were performed on the optimized samples for determining the suitability of the parameters for biomedical applications. RESULTS: A combination of medium laser power, higher laser velocity, and lower hatch distance with values 200 W, 2200 mm/s and 0.08 mm, respectively, was found to be suitable for producing implants. Based on the type of LPBF technology in use, an implant manufacturer can select the initial set of parameters using a similar approach and improve them further based on experimental results. CONCLUSION: The optimized parameters were found to be suitable for developing orthopaedic implants, in terms of physical, mechanical and biological criteria. The methods and results presented in work are expected to assist the implant manufacturers in meeting the expected user requirements and quality standards. GRAPHICAL ABSTRACT: [Image: see text]

A thin-walled copper flange was prepared by the selective laser melting (SLM) method (with the average particle size of pure spherical copper powder of about 35 μm and the focal spot diameter of the single-mode fiber laser of 50 μm). The results show that the wall thickness (about 400 μm) of the obtained sample is significantly larger than that (200 μm, namely desired wall thickness) of the model set before the test. In this study, the wall thickness of the model was set as 50 μm and the linear scanning was adopted. On this basis, the influence laws of SLM parameters (laser power, scanning speed and hatch spacing) on forming quality (relative density, surface roughness and wall thickness) of the thin-walled copper flange sample were studied through an orthogonal test. Moreover, two groups of parameters of the sample with good forming quality were obtained. The thin-walled copper sample with the relative density of about 99.8%, wall thickness of about 200 μm and variance of height of rough surface morphologies (reflecting surface roughness) of 29–36 μm was obtained under linear scanning. Compared with SLM under linear scanning, the surface flatness of the sample is obviously improved and the variance of height of rough surface morphologies is reduced to 13–15 μm after SLM under circular scanning. In this way, the capability of SLM in preparing thinner components is significantly enhanced. The analysis shows that the area of a laser-heated region under scanning along the direction of wall thickness of the copper flange (linear scanning) is about 1.196 times that of the desired shape, and the heated region is wavy with several semicircles connected. Therefore, this is unfavorable for ensuring forming quality and dimensional accuracy of the sample prepared by SLM.

3D-printing is an emerging technology that challenged wrought counterparts by one-step manufacturing for complicated biological devices. However, the material properties and surface features due to manufacturing parameters play an important role on the corrosion behaviour and influence the toxicity of the material as an implant. In this paper, the improvement of pitting potential was observed by electrochemical experiments as the result of grain refinement of DMLS 316 L at 200 W laser power. The ICP results verified the supressed release of toxic cations after the formation of the passive film with enhanced characteristics. However, the pores from DMLS 316 L have the potential to develop into pits when polarised above pitting potential, promoting the risk of using 3D-printed 316 L as implant materials.

Large scale atom interferometers promise unrivaled strain sensitivity to midband (0.1 - 10 Hz) gravitational waves, and will probe a new parameter space in the search for ultra-light scalar dark matter. These atom interferometers require a momentum separation above 10^4 \hbar k between interferometer arms in order to reach the target sensitivity. Prohibitively high optical intensity and wavefront flatness requirements have thus far limited the maximum achievable momentum splitting. We propose a scheme for optical cavity enhanced atom interferometry, using circulating, spatially resolved pulses, and intracavity frequency modulation to overcome these limitations and reach 10^4 \hbar k momentum separation. We present parameters suitable for the experimental realization of 10^4 \hbar k splitting in a 1 km interferometer using the 698 nm clock transition in 87Sr, and describe performance enhancements in 10 m scale devices operating on the 689 nm intercombination line in 87Sr. Although technically challenging to implement, the laser and cloud requirements are within the reach of upcoming cold-atom based interferometers. Our scheme satisfies the most challenging requirements of these sensors and paves the way for the next generation of high sensitivity, large momentum transfer atom interferometers., Comment: 24 pages, 6 figures

Faraday isolator with composite terbium gallium garnet TGG/sapphire magneto-optical elements that were produced by the surface-activated direct bonding method was created. Thermally induced depolarization and thermal lens for composite elements were investigated experimentally and numerically. The resulting structures operated successfully at a high radiation power, providing an isolation ratio exceeding the classical single element made of TGG by 5 dB and amounted to 34 dB at a laser power of 700 W. The maximum operating power at which the isolation ratio was higher than 30 dB was estimated to be over 2 kW, which is almost 3 times more than in the case of a single TGG.

High power laser transmission is being intensively researched as a potential solution to transfer power to remote systems, being the power converter (PC) one of the main limiting factor to improve the system efficiency ( $\eta $ ). Current PCs are mostly horizontal structures in which the $\eta $ heavily decreases at large input power. In this work, we propose a novel GaAs-based vertical-tunnel-junction (VTJ) PC suitable for ultra-high (UH) input power density (P in ). This structure does not suffer from $\eta $ degradation at high P in because it is designed to have low current density, high output voltage and reduced series resistance (~ 2 orders of magnitude lower than the state-of-the-art PCs). We have demonstrated increasing $\eta $ with P in , reaching values higher than 76% at 3000 $\text{W}\cdot $ cm −2 . This vertical-based architecture enables a new set of potential applications for wireless PC to power remote systems with $\eta $ exceeding today’ s state-of-the-art PC designs.

To measure the transmitted laser power in the coronal, middle and apical root thirds during vertical and horizontal irradiation of laser. 14 mm length whole roots and longitudinal root sections were irradiated using a 940 nm diode laser with 0.5 W in continuous mode for 5 s. A power detector was placed in front of the root apex for the vertical transmitted power measurement and placed laterally to root surface for the horizontal transmission experiment. The transmitted power from the root apex vertically was 53% of the irradiated power, while for the horizontal transmission experiment for the coronal, middle and apical root thirds were 25.6%, 40.4% and 41.3%, respectively. Irradiation of root canals with 940 nm laser power can be transmitted during vertical irradiation in more than 50% of the samples, whereas less transmission happens with horizontal irradiation at apical and middle root third than coronal.

Using the Al-Zn-Mg-Cu alloys for the laser melting processes is a challenge due to the formation of hot cracks and pores in the fusion zone. This challenge can be solved by refining the grains, which was achieved in this study. The investigated alloy was modified with 0.5Ti + 0.1B and various Zr concentrations. The microstructure and hardness were studied in the as-cast and pulsed laser melt states (PLM). In the as-cast state, the grains size was reduced 12 times due to forming TiB2 and Al3(Ti, Zr) as heterogeneous nucleation centers. Increasing Zr content to 0.5% led to an increase in the hardness of the base metal to 136.4 HV. After PLM, the microstructure was changed; at low Zr content, large columnar grains were formed. The columnar grains were eliminated when increasing the Zr content, forming small equiaxed grains at the center. Moreover, the hardness of the laser melted zone at low Zr content decreased to 80.5 HV while increasing Zr content to 0.5 wt.% increased the hardness to 99.3 HV. Thus, adding these elements to the investigated alloy improves their properties for high laser power applications.

Integrated fiber components enable compact and robust laser systems but are usually not available with specialty fibers. However, specialty fibers allow power scaling of fiber lasers and amplifiers with all advantages of these fiber designs. In this context, chirally-coupled-core fibers show promising properties for optical fiber components. In this paper, we present the development of a highly-integrated signal and pump combiner in chirally-core-fibers using a side-pumping technology. Combining up to four fiber-coupled pump diodes, a pump-light limited power handling of 600 W can be achieved with an efficiency of 78%. The combiner was tested in a side-pumped single-frequency all-fiber amplifier but can also be implemented in almost any fiber laser or amplifier.

The magnetometer is a multi-parameter system, parameters optimization is always the problem to improve the sensitivity of the atomic magnetometer. Multiple parameters hardly decide the optimized conditions in the experiments because of the influence of several parameters and parameters may interact with each other. Besides, the influence of parameters on the signal-to-noise ratio can hardly be analyzed theoretically due to the complex physical configuration. We used a generalized polynomial chaos expansion to construct an agent model for the SERF atomic magnetometer to replace its complex physical model, and used a variance-based sobol method to perform a global sensitivity analysis of the parameters in this paper. The mathematical method of uncertainty quantification is used to comprehensively analyze six parameters’ effect on SERF atomic magnetometer performance. The results show that the probe laser power has the greatest impact on the atomic magnetometer, and it is the parameter with the highest degree of linearity with the atomic magnetometer. In accordance with the results of the uncertainty quantification analysis, the parameters of the probe laser power of the SERF atomic magnetometer were experimentally optimized, and the performance of the magnetometer was significantly improved.

Selective laser melting (SLM) is a promising additive manufacturing process for fabricating complex geometries of metallic parts. The SLM processing parameters can have a major effect on microstructure and mechanical behavior of the fabricated metallic parts. In this work, the effect of laser spot size, hatch spacing, energy density, scan strategy, scanning speed and laser power on the microstructure and mechanical behavior of SLM-processed 316L stainless steel samples has been studied. These samples processed with different processing parameters were characterized by performing microhardness, tensile tests, x-ray diffraction (XRD) analysis, Energy dispersive spectroscopy (EDS) and scanning electron microscopy (SEM) analysis. The samples fabricated with a larger laser spot size exhibited higher tensile strength as well as higher microhardness values. A similar trend was observed for samples processed with higher laser power and hatch spacing. For the same energy density, higher laser power and lower scanning speed significantly enhance the mechanical properties of SLM processed samples compared to those fabricated with lower laser power and higher scanning speed. Therefore, it can be concluded that laser power has a more dominant role in governing the mechanical properties of SLM processed parts than scanning speed.

Journal of materials science 2021, 1-15 (2021). doi:10.1007/s10853-021-06577-8, Laser powder bed fusion is an additive manufacturing process that employshighly focused laser radiation for selective melting of a metal powder bed. Thisprocess entails a complex heat flow and thermal management that results incharacteristic, often highly textured microstructures, which lead to mechanicalanisotropy. In this study, high-energy X-ray diffraction experiments were carriedout to illuminate the formation and evolution of microstructural featuresduring LPBF. The nickel-base alloy Inconel 625 was used for in situ experimentsusing a custom LPBF system designed for these investigations. The diffractionpatterns yielded results regarding texture, lattice defects, recrystallization, andchemical segregation. A combination of high laser power and scanning speedresults in a strong preferred crystallographic orientation, while low laser powerand scanning speed showed no clear texture. The observation of a constantgauge volume revealed solid-state texture changes without remelting. Theywere related to in situ recrystallization processes caused by the repeated laserscanning. After recrystallization, the formation and growth of segregations werededuced from an increasing diffraction peak asymmetry and confirmed by exsitu scanning transmission electron microscopy., Published by Springer Science + Business Media B.V, Dordrecht [u.a.]

This paper focuses on improving the melt pool geometry predictions and quantifying uncertainties using an adapted version of the Eagar–Tsai (E–T) model that incorporates temperature-dependent properties of the material as well as powder conditions. Additionally, Bayesian inference is employed to predict distributions for the E–T model input parameters of laser absorptivity and powder bed porosity by incorporating experimental results into the analysis. Monte Carlo uncertainty propagation is then used with these parameter distributions to estimate the melt pool depth and associated uncertainty. Our results for the 316L stainless steel suggest that both the absorptivity and powder bed porosity are strongly influenced by the laser power. In contrast, the scanning speed has only a marginal effect on both the absorptivity and powder bed porosity. We constructed a printability map using the Bayesian E–T model based on power-dependent input parameter values to demonstrate the merit of the approach. The Bayesian approach improved the accuracy in predicting the keyhole regions in the laser power-scan speed parameter space for the 316L stainless steel. Although applied to a specific adaptation of the E–T model, the method put forth can be extended to quantify uncertainties in other numerical models as well as in the estimation of unknown parameters.

This study explores the laser-arc hybrid welding process of high nitrogen steel (HNS) in order to circumvent the problem of welding porosity. The influence of welding heat input on welding porosity has been elucidated by analyzing the changes in the morphological characteristics of the laser keyhole and the molten pool temperature. The results show that the pore ratio increases with a rise in laser power. Meanwhile, the pore ratio first decreases and then increases as the welding current intensifies. Additionally, it decreases as the welding speed and defocus amount increase. The lowest pore ratio of the weld is considered as the desired value, and the response surface method (RSM) is used to optimize the heat input parameters. When the laser power ranges from 2.80 to 2.85 kW, the welding current becomes 260 A, welding speed ranges from 0.73 to 0.80 m/min, defocus amount ranges from 0 to 1 mm, and pore ratio of the weld exhibits its minimum value (4.29 to 4.67%).

In this paper, SiCp/Al composites were successfully fabricated by selective laser melting (SLM), and the dependence of phase composition, densification behavior, and mechanical properties of the composites on laser power was researched and discussed. The results showed that the density, microhardness and friction resistance of the SLM formed SiCp/Al composites were enhanced with increasing the laser power density, which may be caused by the higher molten pool temperature at higher laser power density. When SiCp/Al composites were prepared at 400 W with a scanning speed of 300 mm/s, the highest relative density of approximately 91.1 % and microhardness of approximately 191 HV0.1 (more than six times higher than that of the selective laser melted pure Al specimens, 191 HV0.1 vs 31 HV0.1) were obtained, and the minimum wear rate and friction coefficient were 1.31 × ×10−5 mm3 N−1 m−1 and 0.38, respectively.

Stable output and beam profile at high power laser operation is a prime requirement for precision high-end manufacturing. The stability of laser charateristics during power scaling in a single-oscillator is limited by several unavoidable non-linear effects. Hence, kW-level power scaling through multiple amplification stages or using signal combination are feasible solutions. In a master oscillator power amplifier (MOPA) architecture, pump-signal combiner with high pump coupling efficiency and low loss signal transmission maintaining seed beam quality during coupling from a single mode fiber into a large mode area fiber, is an important component. In this respect, an effective method of fabricating mode-field matched pump-signal combiner has been presented employing a section of intermediate fiber, having adiabatically tapered core and uniform cladding, along with a conventional signal fiber (termed hybrid signal fiber) inside the input fiber bundle to obtain effective mode-field matching of signal light in between the input fiber bundle and the output fiber. Additionally a taper-less signal combiner design has been proposed for scaling laser power through incoherent combination. The reduced-clad signal fiber with low loss core guidance supports bundling of the input fibers inside an economic low-OH silica tube to obtain good transmission efficiency and beam profile.

In recent years, the application of aluminum-based hybrid nanocomposites has been developed in industries like automotive and aerospace due to their remarkable properties. Hence, the machinability investigation of these materials is essential. In this research, laser-assisted machining was performed on aluminum based hybrid nanocomposite samples fabricated by the electromagnetic stir casting method. Continuously, the effects of process parameters namely laser power, depth of cut and cutting speed on the surface roughness, cutting force and temperature were assessed by Design of Experiments (DOE) technique. Taguchi standard orthogonal method (L9 (33)) was used to analyze the process factors. Based on the results, depth of cut had no effect on the surface temperature. Moreover, cutting speed and depth of cut exhibited the major influence on the surface roughness and cutting force, respectively. The optimal cutting conditions were obtained for surface roughness at laser power of 450 W, cutting speed of 30 m/min, and cutting depth of 0.2 mm and were obtained for cutting force at laser power of 450 W, cutting speed of 30 m/min, and cutting depth of 0.1 mm.

Purpose For the laser powder bed fusion (L-PBF) technology, the side surface quality is essentially important for industrial applicated parts, such as the inner flow parts. Contour is generally adopted at the parts’ outline to enhance the side surface quality. However, the side surface roughness (Ra) is still larger than 10 microns even with contour in previous studies. The purpose of this paper is to study the influence of contour process parameters, laser power and scanning velocity on the side surface quality of the AlSi10Mg sample. Design/methodology/approach Using L-PBF technology to manufacture AlSi10Mg samples under different contour process parameters, use a laser confocal microscope to capture the surface information of the samples, and obtain the surface roughness Ra and the maximum surface height Rz of each sample after analysis and processing. Findings The results show that the side surface roughness decreases with the increase of the laser power at the fixed scanning velocity of 1,000 mm/s, the side surface roughness Ra stays within the error range as the contour velocity increases. It is found that the Ra increases with the scanning velocity increasing and the greater the laser power with the greater Ra increases when the laser power of contour process parameters is 300 W, 350 W and 400 W. The Rz maintain growth with the contour scanning velocity increasing at constant laser power. The continuous uniform contour covers the pores in the molten pool of the sample edge and thus increase the density of the sample. Two mechanisms named “Active adhesion” and “Passive adhesion” cause sticky powder. Originality/value Formation of a uniform and even contour track is key to obtain the good side surface quality. The side surface quality is determined by the uniformity and stability of the contour track when the layer thickness is fixed. These research results can provide helpful guidance to improve the surface quality of L-PBF manufactured parts.

The currently available high-power laser presents significant opportunities for welding of thick section components in single-pass. However, weld defects frequently occur and depth of penetration is usually lower than expected in this situation. In this work, a process of laser welding under reduced ambient pressure was investigated to achieve a single-pass complete-joint-penetration weld of 20 mm-thick high-strength steel. An experimental and theoretical program of investigation was undertaken to evaluate the characteristic of this welding process. The weld appearance, porosity inside the weld metal, microstructure and mechanical properties of weld joint were examined experimentally. The temperature field was calculated numerically using a 3D heat transfer and fluid flow model. A defect-free sound weld joint of 20 mm-thick plate was obtained just using an 8-kW laser power. The weld joint showed a very high aspect ratio characteristic of electron beam welding. From base metal (BM) to fusion zone (FZ) through heat-affected zone (HAZ), the microhardness varied significantly duo to their different microstructures resulted from the various peak temperatures and cooling rates for varying distances from weld center. All the tensile test samples fractured at the BM away from HAZ and FZ, which suggested that the welded metal was stronger than BM. The calculated weld geometry agreed with the corresponding experimental results through considering the role of ambient pressure. Their good agreement indicated the validity of the potential causative variables considered in the simulations. The modelling results also showed that the weld pool had a lower peak temperature and thinner liquid weld metal around keyhole under reduced ambient pressure.

The conventional fabrication methods for enrichment microfluidic devices require cleanroom, which are costly and time-consuming. Developing a facile and low-cost method to fabricate microfluidic chips could stimulate the progress of the applications of those chips. Here, we present an easy method for fabrication of a complete PDMS (Polydimethylsiloxane) microfluidic chip used for ion and protein enrichment. The method consists of three main fabrication steps: PDMS microchannels ablation by co2 laser, nation membrane deposition, and oxygen plasma assist bonding under pressure. To fabricate a desired microchannel, the laser ablation parameters, containing laser power and ablation speed, were analyzed. The parameters for oxygen plasma assist bonding were also investigated to improve the bonding quality of the chips (low dimension loss and high bonding strength). The following Rhodamine B enrichment tests demonstrate that the presented method allows fabrication of microfluidic chips with precise dimensions and leakage free.

A hybrid metal additive manufacturing method for complex structures and high-precision parts was investigated to realize both high-efficiency forming with wire arc additive manufacturing (WAAM) and precise forming with laser metal deposition (LMD). In this method, a part is decomposed into sub-volumes. Then, the sub-volumes with relatively simple structural features are formed through WAAM as a substrate, and the other sub-volumes with more complex structures or small-sized features are formed through LMD on this substrate. However, the mechanical properties of the bonding interface could be reduced if the latter sub-volumes were directly deposited by LMD on the rough WAAM substrate surface. In order to avoid unnecessary machining processes between WAAM and LMD for high efficiency and ensure the mechanical properties of the WAAM–LMD bonding interface, a laser remelting method was applied to improve the profile of the WAAM substrate surface. A simulation model of the heat transfer and fluid flow in the laser remelting process was established, and the influences of the laser power and scanning speed on the surface-profile improvement were researched by simulation and verified by experiments, which allowed the remelting process parameters to be optimized. Furthermore, the LMD-formed volumes were deposited directly on the WAAM-formed substrate after surface milling and laser remelting. Then, the microstructures and shear properties of the bonding interfaces formed using the three process methods were compared, and the feasibility of using the laser remelting method to improve the bonding interface performance was verified.

In this work, phosphor-converted white laser diodes (pc-WLDs) with high color quality were fabricated by combining blue lasers and bicolor phosphor-in-glass (PiG) converters. The bicolor PiGs were prepared by printing and sintering green/red phosphor glass films on sapphire substrates, and then applied in the transmission type of pc-WLDs. The PiG-based white laser diodes (WLDs) display broadband emission and their optical performances were adjusted by varying the PiG film thickness. When the film thickness increases from 80 to $160~\mu \text{m}$ , the luminous flux and correlated color temperature (CCT) of PiG-based WLDs are gradually decreased, and they still have high color rendering index (CRI). At the film thickness of $160~\mu \text{m}$ , the PiG-based WLD achieves high color quality with a CRI of ${R}_{a} = {88}$ , ${R}_{{9}} = {91}$ , and ${R}_{{13}} = {93}$ , a CCT of 4571 K, and a chromaticity coordinate of (0.3525, 0.3541) at a laser power of 2.4 W. Furthermore, the PiG-based WLD has stable color quality at high laser power and the luminous flux reaches to 553 lm at a laser power of 5 W. The results indicate that the bicolor PiG-based WLDs realize high-quality white light, which can promote the practical applications of laser lighting in high-quality fields.

A high-power monolithic continuous wave (CW) Yb doped fiber amplifier at 1064 nm has been demonstrated based on traditional large mode area step-index fiber, which generated 5.07 kW narrow line-width laser with near diffraction-limited beam quality. At the maximal output power, >35dB OSNR has been achieved with line-width being 370pm, and the measured beam quality is M2x = 1.252, M2y = 1.322. The influence of cooling temperature on SRS has been investigated in high power fiber lasers, which shows that the SRS at 4kW has been suppressed 24 dB by lowering the temperature from 20°C to 8°C. To the best of our knowledge, this is the highest narrow line-width laser power generated from the traditional large mode area step-index monolithic fiber amplifier.

The natural characteristics of sintered ceramics limit the micromachining of functional surface textures in terms of tool wear, processing quality and economic effectiveness. So, the micro-machining of green ceramics before completely sintering is introduced. In this paper, micro-channels are fabricated on the surfaces of green ceramics pretreated by different annealing temperatures. The effect of parametric combination of annealing temperature and laser parameters on the response of processing quality, channel dimension and material removal rate (MRR) are studied by single fact experiments and multi-objective optimization by the response surface method (RSM). The mathematical models of the interaction between different factor combinations are developed based on RSM. Results show that the annealing temperature has significant influence on the aspect ratio under different laser parameters. Continuous channels with few recast layers are always formed at the annealing temperatures of 500–800 °C and a higher annealing temperature always contributes to a larger aspect ratio. Based on the responses of RSM, the optimal parameters of laser ablation and annealing temperature are chosen as laser power of 6 W, scanning speed of 350 mm/s, laser frequency of 40 KHz, and the pretreatment annealing temperature of 750 °C. The experiments validate good agreement of proposed model.

Selective laser melting (SLM) is an advanced, efficient and capable manufacturing technology that utilizes a laser for heating metal or alloy powders to melt and solidify directly into metal parts. In this paper, the smoothed particle hydrodynamics (SPH) method was employed for the three-dimensional numerical simulation of the SLM process. This method is significantly benefit for solving free surface flows and complex motions at multiple material phase interfaces. The weakly compressible equation of state and Navier-Stokes equation were used to describe the state and flow of the liquid metal in the process of the SLM mathematical modelling. The surface tension and wetting effect are critical for the morphology and evolution of the molten pool. A continuous surface tension model and a wetting effect model were established, and the correctness of these mathematical models was verified by the evolution of the liquid droplets over time. Then, a special material model was established based on the thermophysical properties of 304L stainless steel. A Gaussian heat source model was employed to heat the metal powder in the SLM process. In this work, the SPH method was used to simulate the morphology and formation of the molten pool at different laser powers and to analyse the effect of different laser powers on the size of the molten pool. The simulation results show that the surface tension and wetting effect under laser action play an important role in the expansion of the molten pool size; within a certain laser power range, the size of the molten pool gradually increases with increasing laser power, and the simulation calculation results are in good agreement with the experimental results. The results show that the SPH method is a viable and promising way to simulate the SLM process.

An azobenzene (azo)-integrated asymmetric dual-S-taper fiber interferometer based on concatenated single-mode fiber S-tapers is proposed and fabricated. As the fiber interferometer is immersed into the ethyl orange (EO) solution, due to the photo-isomerization effect of azo materials, azo molecules would experience conformal change when 473 nm laser illumination is applied, resulting in the variation of ambient surrounding refractive index. Transmission spectra of the proposed dual-S-taper structure exhibit stable and regular wavelength shift under different illumination light intensities or EO weight percentages of EO solutions. An optimal EO weight percentage of 0.1 wt% was experimentally acquired with wavelength sensitivity reaching −27.6 pm/mW for a laser power range of 0 mW to 195 mW. Furthermore, repeated laser power increasing and decreasing experiments and the control experiment under the distilled water environment proves our proposed fiber interferometer with highly reversible and stable light-sensitive wavelength responses, making it a good candidate for light intensity sensing and light-controlled wavelength-tuning applications in future all-optical networking systems.

The nickel-based Colmonoy-5 hardfacing alloy is used to hard-face 316LN austenitic stainless steel components in fast reactors. The nominal composition (in wt%) was listed as follows: 0.01 C, 0.49 Si, 0.87 Mn, 17.09 Cr, 14.04 Ni, 2.56 Mo, 0.14 N, and balance Fe. Hardfacing is a technique of applying hard and wear-resistant materials to substrates that need abrasion resistance. The thickness of hardfacing deposit varies between 0.8 mm and 2 mm based on parameter combinations. In this study, laser hardfacing process parameters including laser power, powder feed rate, travel speed, and defocusing distance were optimized to reduce weight loss of laser hard-faced Ni-based deposit. The tribological characteristics of reactor-grade NiCr-B hard-faced deposits were investigated. The RSM technique was used to identify the most important control variables resulting in the least weight loss of the nickel-based alloy placed on AISI 316LN austenitic stainless steel. Statistical techniques like DoE and ANOVA are utilized. Changing the laser settings may efficiently track the weight loss of laser hard-faced nickel alloy surfaces. These are created using the response surface technique. The deposit produced with a laser power of 1314 W, powder feed rate of 9 g/min, travel speed of 366 mm/min, and defocusing distance of 32 mm had the lowest weight loss of 16.4 mg. Based on the F value, the powder feed rate is the major influencing factor to predict the hardness followed by power, travel speed, and defocusing distance.