Influence Of Laser Power Research Articles

Effect of laser power on the grain morphology and microhardness of dual laser-beam bilateral synchronous welded 2219 aluminium alloy T-joint

Dual laser-beam bilateral synchronous welding (DLBSW) technology has been widely used in the connection of skin-stringer T-joint. In this study, DLBSW technology was performed to fabricate T-joint of 2219 aluminium alloy. Furthermore, the effect of laser power on grain morphology and microhardness of the T-joint was investigated. The microstructure of different parts was observed and the grain size was quantitatively analysed. The results show that the grain quantity and microhardness of the welded joint are increased significantly as the welding heat input increases. It is found that the influence of laser power on the grain size at the edge of the weld seam is greater than that in the centre of weld. Besides, the microhardness of the non-dendritic equiaxed zone decreases with the increase of laser power, which is caused by the decrease of Al element.

Hydrogen-Bonding-Induced H-Aggregation of Charge-Transfer Complexes for Ultra-Efficient Second Near-Infrared Region Photothermal Conversion

Hydrogen-Bonding-Induced H-Aggregation of Charge-Transfer Complexes for Ultra-Efficient Second Near-Infrared Region Photothermal Conversion

The Influence of Laser Power and Butt Gap on the Droplet Transfer and Weld Formation of Laser Arc Hybrid Welding

In this study, an 8mm thick AH36 steel plate was welded using laser + MAG hybrid welding technology. The results show that when the laser power is low, the droplet transition form is droplet transition, the droplet size is larger, and the transition frequency is low. As the laser power increases, the form of droplet transition is jet transition, the droplet size is small, and the transition frequency is high. When the laser power is low, the undercut phenomenon of the weld is serious. With the increase of the laser power, the undercut phenomenon of the weld is improved. Besides, the weld width and welding seam reinforcement will also increase. Laser-arc hybrid welding has a certain gap adaptability. When the laser power is 10KW, the weld profile of 0mm welding gap and 1mm welding gap are basically the same. Properly reducing the laser power is conducive to the larger welding assembly gap of laser arc hybrid welding.

Parametric Study of Laser Welding on Polyamide using Design of Experiments

Laser welding was primarily employed for metals but recent developments in laser technology have enabled its applications in the polymers field. Laser transmission welding or joining of two polymers and metal-polymer has become feasible. The study was mainly aimed to investigate the influence of laser power, speed of welding, and number of passes based on Taguchi orthogonal array on responses by using continuous mode high power diode fiber laser on polyamide. The weld quality was assessed by measuring the strength of weld and width of the weld seam. Initial study on diode fiber laser welding machine and the parameters associated with it was essential to design the experimental layout. Polyamide, which is widely used in the automotive industry was selected as the material and the influence of various parameters on the laser welds were studied using design of experiments. The experimental studies were performed based on orthogonal array method. The responses of the weld were measured using an optical metallurgical microscope. The ideal parameters for maximum joint strength and minimum weld width are investigated using Taguchi method. The multi-objective optimization has been done by applying grey relational analysis to identify the levels of factors that result in the maximum strength and minimum weld seam width.

Influence of Pulsed Exposure Strategies on Overhang Structures in Powder Bed Fusion of Ti6Al4V Using Laser Beam

Manufacturing structures with low overhang angles without support structures is a major challenge in powder bed fusion of metals using laser beam (PBF-LB/M). In the present work, various test specimens and parameter sets with continuous wave (cw) and pulsed exposure are used to investigate whether a reduction of downskin roughness and overhang angle can be achieved in PBF-LB/M of Ti6Al4V. Starting from cw exposure, the limits of overhang angle and surface roughness at the downskin surface are investigated as a reference. Subsequently, the influence of laser power, scanning speed, and hatch distance with fixed pulse duration (τpulse = 25 µs) and repetition rate (υrep = 20 kHz) on surface roughness Ra is investigated. Pulsed exposure strategies enable the manufacturing of flatter overhang angles (≤20° instead of ≥25°). Furthermore, a correlation between the introduced volume energy density and the downskin roughness can be observed for pulsed exposure. As the reduction in volume energy density causes an increase in porosity, the combination of pulsed downskin exposure and commercial cw infill exposure is investigated. The larger the gap in volume energy density between the infill area and downskin area, the more challenging it is combining the two parameter sets. By combining cw infill and pulsed downskin exposure, flatter overhang structures cannot be manufactured, and a reduction in roughness can be achieved.

Influence of laser parameters on segregation of Nb during selective laser melting of Inconel 718

A transient three-dimensional powder-scale model was established for understanding the flow field and mass transfer within the molten pool during the selective laser melting (SLM) of Inconel 718 alloy by considering some important physical phenomena, such as, a transition from powder to solid, nonlinearities produced by temperature-dependent materials’ properties, and fluid flow in the calculation. The influence of laser power or scanning speed on the flow field and cooling rate was discussed in detail. The simulation results reveal that the motion of molten pool and higher cooling rate promote the mass transfer and benefit the solute distribution by increasing laser power. However, with increasing the scanning speed, the melt flow speed and cooling rate are elevated, resulting in an agglomeration of the solute elements, which is ascribed to the shorter dwelling time of liquid. Therefore, the segregation of Nb can be effectively suppressed by increasing laser power or decreasing scanning speed, which can decrease the dwelling time of liquid.

Study on the damage effect of optical detector irradiated by CW laser

In order to study the damage effect of continuous laser on optical detectors, an equivalent experimental method of laser irradiated optical detectors was designed and constructed in the laboratory. The damage mechanism and phenomenon of the laser are analyzed through experiments, and the power density of the laser to the target and the size of the saturated spot on the surface of the detector are measured, and the corresponding relationship between the saturation of a single pixel of the detector and the power of the laser to the target is obtained, which reveals the influence of laser power on detection The influence law of the interference characteristic of the device. The experimental results show that under the condition that the diameter of the laser beam and the distance to the target are the same, as the power of the laser to the target increases, the saturated spot size of the detector (that is, the number of saturated pixels) increases, and the saturated spot size increases with the power within the error range. The relationship is approximately linear; for a typical optical detector, the laser power at which the pixels are disturbed by saturation is a fixed value. Increasing the laser power can increase the number of saturated pixels, and the area disturbed by laser saturation is further expanded.

COMSOL SIMULATION OF LASER WELDING OF ALUMINUM

This research includes a Comsol Mutiphysics model describing the temperature distribution on aluminum during the laser conductivity welding process. The influence of laser power and speed on the welding process is discussed and compared with experiments. Numerical simulations of laser welding process have been performed to determine the temperature fields of laser impact to samples of aluminum. Numerical calculations are made for fiber laser. The plots of the temperature dependence on the surface and in the depth of aluminum samples on the velocity are analyzed for several power densities for this laser.

The influence of laser power and scanning speed on the dimensional accuracy of SLS formed parts

In SLS sintering forming, laser power and scanning speed are two important process parameters, which directly affect the dimensional accuracy of sintered parts. Using PA2200 powder as the forming material, the influence of laser power and scanning speed on the dimensional accuracy of the sintered part was analyzed. Through theoretical analysis and experimental verification, the best combination of parameters was obtained. The laser power is 40 W and the scan speed is 5000 mm/s. The dimensional accuracy of the sintered parts is obtained by X-direction deviation -0.35 %, Y-direction deviation -0.4 %, and Z-direction deviation -0.25 %.

Investigating the elastic modulus and hardness properties of a high entropy alloy coating using nanoindentation

Using a focused ion beam TTX-NHT3 Nanoindentation tester with a load of 500 mN, we study the micromechanical properties of laser-deposited AlCoCrFeNiCu high entropy alloy coatings. The indentation tests conducted were used to examine the influence of laser power and scan speed on the elastic modulus and hardness of the alloy coatings using the Oliver & Pharr method. There were several indentation points impressed and used to extract the mechanical properties of the alloys, and the results of the alloy were compared with that of the A301 steel substrate. The results showed the mean value of the NanoHardness and Elastic modulus of the high entropy alloy were 2.769 GPa and 149 GPa, respectively. The Vickers hardness showed a 60% decline as the laser power increased from 1200 W to 1600 W. The hardness and the elastic modulus were proportional to each other, both increasing with a decrease in the indentation depth and laser power. The laser-deposited high entropy alloys were more resistant to plastic deformation and had improved mechanical properties than the steel substrate attributed to the solid-solution hardening and lattice distortion effect of the BCC phase structure and aluminium contents, respectively.

Sequential Self-Folding of Shape Memory Polymer Sheets by Laser Rastering Toward Origami-Based Manufacturing

Abstract Origami-based fabrication strategies open the door for developing new manufacturing processes capable of producing complex three-dimensional (3D) geometries from two-dimensional (2D) sheets. Nevertheless, for these methods to translate into scalable manufacturing processes, rapid techniques for creating controlled folds are needed. In this work, we propose a new approach for controlled self-folding of shape memory polymer sheets based on direct laser rastering. We demonstrate that rapidly moving a CO2 laser over pre-strained polystyrene sheets results in creating controlled folds along the laser path. Laser interaction with the polymer induces localized heating above the glass transition temperature with a temperature gradient across the thickness of the thin sheets. This gradient of temperature results in a gradient of shrinkage owing to the viscoelastic relaxation of the polymer, favoring folding toward the hotter side (toward the laser source). We study the influence of laser power, rastering speed, fluence, and the number of passes on the fold angle. Moreover, we investigate process parameters that produce the highest quality folds with minimal undesired deformations. Our results show that we can create clean folds up to and exceeding 90 deg, which highlights the potential of our approach for creating lightweight 3D geometries with smooth surface finishes that are challenging to create using 3D printing methods. Hence, laser-induced self-folding of polymers is an inherently mass-customizable approach to manufacturing, especially when combined with cutting for integration of origami and kirigami.

Effect of Laser Heat Treatment on the Mechanical Performance and Microstructural Evolution of AISI 1045 Steel-2017-T4 Aluminum Alloy Joints during Rotary Friction Welding

This paper evaluates the influence of laser power on the rotary friction welding (RFW) process to improve the mechanical performance and microstructural evolution of AISI 1045 steel and 2017-T4 aluminum alloy joints. As part of this evaluation, the absolute chemical determination of these materials was precisely measured using a GDOES bulk analysis. The application of laser power during friction welding is known as laser-assisted friction welding. To evaluate the effect of the energy from the laser on the rotary joining process of steel-aluminum, a laser-assisted rotary friction welding process was set up, and a design of experiments (DOE) applied. First, a DOE consisting of two factors at two levels was used to evaluate the effect of friction pressure and rotational speed on the hardness and tensile strength of the weldment. Then, a mixed DOE of three factors at two and three levels was implemented to investigate the effect laser heat treatment has on the process. It was concluded that the application of a laser heat treatment plays a significant role in the resulting mechanical performance and microstructural evolution of RFW steel-aluminum joints. Increasing both the ultimate tensile strength and the thickness of the Al(Fe, Cu) interface reaction layer between the joined materials.

Research on surface finish of thin-wall parts by laser with coaxial inside-beam powder feeding

Surface quality is an important performance indicator of laser metal deposition. Based on annular laser beam internal powder feeding technology, the effect of higher energy of the outer side of the annular beam on the surface roughness and waviness of thin-wall parts is studied in this paper. The influences of laser power, scanning speed, and powder feeding rate on the surface finish of thin-wall parts are investigated. The results show that the laser power has a significant effect on surface finish. With the increase in laser power, the roughness decreases and the waviness increases first and then decreases. High laser power can improve surface finish. As the scanning speed increases, the roughness decreases first and then increases, and the waviness decreases. The scanning speed has a significant influence on surface waviness. Increasing the powder feeding rate is not beneficial to surface quality because the value of the roughness and the surface waviness will add with its rising.

Influence of laser power and welding speed on dendrite structure growth of low power pulsed laser welded super alloy

The influence of different welding parameters like welding speed and laser power on microstructure and the mechanical properties of low power pulsed Nd: Yag laser welded Nickel based super alloy inconel 617 sheets of thickness 1.5 mm has been investigated. In the present study, the welding of the specimens was done in a single pass aimed to full depth penetration. The microstructure of the various samples at fusion zone and at heat affected zone was characterized by field effect scanning electron microscope (FESEM) while the weld size of the welded metal at different parameters were measured using optical microscope (OM). The microhardness in the various zones for the welded sample has also been investigated. The microhardness of the welded samples was compared with base metal after experimental observations. The XRD technique was used to analyze the crystallography of the material at (2θ degree). The material has been used for the present study because of its exceptional properties of heat resistant and corrosion resistant. The Nd: YAG pulsed laser has been used because of its overlapping factor during welding that reduces porosity in the weld zone.

Effect of porosity morphology and elements characteristics on mechanical property in T-joints during dual laser-beam bilateral synchronous welding of 2060/2099 Al-Li alloys

The 2 mm thick 2060-T8/2099-T83 Al-Li alloy T-joints were welded by dual laser-beam bilateral synchronous welding (DLBSW) with ER4047 filler wire. The metallurgical porosity defects under different welding parameters were investigated to study the influence of laser power and weld speed on the porosity distribution, formation mechanism and mechanical properties during DLBSW process. In order to explore the special effect of welding heat input on the difference of alloying elements content around porosity, a comparative analysis of elements content between the porosity boundary and matrix around porosity was studied. It was found that the weld porosity defects were increased significantly as the laser power increased. Besides, the heat affected zone (HAZ) and branches of dendritic crystals were the key positions of porosity nucleation and formation. The results of tensile test and SEMoffailuresurface demonstrated that porosity was one of the important factors leading to weld bead failure. In particular, the porosity in the bottom fusion zone and EQZ significantly weakened the performance of the T-joint.

Inner strut morphology is the key parameter in producing highly porous and mechanically stable poly(ε-caprolactone) scaffolds via selective laser sintering

Selective laser sintering (SLS) is an established method to produce dimensionally accurate scaffolds for tissue engineering (TE) applications, especially in bone. In this context, the FDA-approved, biodegradable polymer poly(ε-caprolactone) (PCL) has been suggested as a suitable scaffold material. However, PCL scaffold mechanical stability – an attribute of particular importance in the field of bone TE – was not considered as a primary target for SLS process parameters optimization so far. Here, we investigated the influence of SLS process parameters on the sintered scaffolds with the aim of producing highly porous (>70% porosity) PCL scaffolds with sub-mm geometrical features for bone TE. Specifically, we studied the influence of laser power, beam compensation and laser beam diameter on the dimensional accuracy and mechanical stiffness of the produced PCL scaffolds. We found that the ratio between the diameter of the molten cross-section within scaffold struts and the outer strut diameter (including partially sintered particles) depended on the SLS process parameters. By maximizing this ratio, the mechanical stability could be optimized. The comparison with in silico predictions of scaffold mechanical stiffness revealed that the diameter of the molten cross-section within struts and not the strut diameter controlled the mechanical behaviour of the scaffold. These observations should be considered when evaluating the quality of the sintering process based on dimensional accuracy, especially for features <1 mm. Based on these findings, we suggested an approach to evaluate the sintering outcome and to define SLS process parameters that enable the production of highly porous scaffolds that are both dimensionally accurate and mechanically stable. Moreover, the cytocompatibility of PCL scaffolds was evaluated by elution tests with primary human mesenchymal stromal cells. No evidence of cytotoxicity was found in any of the investigated scaffolds, confirming the suitability of SLS as production technique of PCL scaffolds for bone TE over a wide range of SLS process parameters.

A Comparative Analysis of Laser Additive Manufacturing of High Layer Thickness Pure Ti and Inconel 718 Alloy Materials Using Finite Element Method

Investigation of the selective laser melting (SLM) process, using finite element method, to understand the influences of laser power and scanning speed on the heat flow and melt-pool dimensions is a challenging task. Most of the existing studies are focused on the study of thin layer thickness and comparative study of same materials under different manufacturing conditions. The present work is focused on comparative analysis of thermal cycles and complex melt-pool behavior of a high layer thickness multi-layer laser additive manufacturing (LAM) of pure Titanium (Ti) and Inconel 718. A transient 3D finite-element model is developed to perform a quantitative comparative study on two materials to examine the temperature distribution and disparities in melt-pool behaviours under similar processing conditions. It is observed that the layers are properly melted and sintered for the considered process parameters. The temperature and melt-pool increases as laser power move in the same layer and when new layers are added. The same is observed when the laser power increases, and opposite is observed for increasing scanning speed while keeping other parameters constant. It is also found that Inconel 718 alloy has a higher maximum temperature than Ti material for the same process parameter and hence higher melt-pool dimensions.

Study on the mechanism of surface topography evolution in melting and transition regimes of laser polishing

Previous studies on the mechanism of laser polishing were limited to the melting regime, this paper proposed a numerical model for the melting and transition regimes of laser polishing, which coupled heat transfer, fluid flow, and material vaporization. Based on the model, the evolution of the temperature and velocity fields of the molten pool in laser polishing was presented. And the mechanism of surface topography evolution was revealed from the perspective of surface forces (capillary force, thermocapillary force, and recoil pressure), fluid velocity, and material removal. Furthermore, the corresponding relationships between surface forces, fluid velocity, and surface topography were determined. The contributions of surface forces and vaporization front velocity in laser polishing were investigated, and the reason for the formation of the bulge structure and the influence of laser power on it were analyzed. And the velocity direction change points which have a great influence on the surface evolution were found, and the method to determine the positions of these points was proposed. Besides, the surface roughness prediction after laser polishing was tried through the numerical model, and the maximum error between the predicted results and the experimental results is 14.9%. Therefore, this model can be used to optimize process parameters.

Laser Metal Deposition of Inconel 718 Alloy and As-built Mechanical Properties Compared to Casting.

In the last years, powder-based Laser Metal Deposition (LMD) has been attracting attention as a disruptive Additive Manufacturing (AM) technique for both the fabrication and restoration of Inconel 718 components, enabling to overcome current limitations faced by conventional manufacturing processes in terms of manufacturing costs, tool wear, and lead time. Nevertheless, the uncertainty related to the final mechanical performance of the as-built LMD parts limits a wider adoption of such technology at industrial level. This research work focuses on the mechanical characterization of as-built Inconel 718 specimens through split Hopkinson tensile bar tests performed at different strain rate conditions. The influence of laser power on the final mechanical behavior of the as-built tensile samples is discussed and compared with the mechanical response of as-cast ones. The as-built specimens exhibit a high internal density (i.e., 99.92% and 99.90% for 300 W and 400 W, respectively) and a more ductile behavior compared to the as-cast ones for every evaluated strain rate condition. The strain hardening capacity of the as-built samples increases with the laser power involved in the LMD process, reaching an average Yield Strength of 703 MPa for specimens realized at 400 W and tested at 800/s.

Influence of laser power on interface characteristics and cracking behavior during laser remanufacturing of nodular cast iron

Nodular cast iron shows poor weldability due to obvious crack tendency caused by chilled structure in interface region during welding and cladding process. However, chilled structure could be eliminated by controlling interface heat input during laser cladding process. In this paper, brazing interface characteristic with no chilled structure could be obtained by controlling the heat input of the interface, and the results showed that the brazing interface illustrated higher strength compared with the chilled structure interface. The results illustrated that the tensile strength of specimens with brazing and intermittent chilled structure characteristic could reach 564 MPa. However, tensile strength of specimens with continuous chilled structure characteristic was lower than 353 MPa. Cracks formed in the interface zone and extended to the ledeburite region. FEM method with the help of ANSYS software was adopted to determine the thermal cycles of the interface region during the cladding process, and the mechanism of the interface behavior was studied.