High Power CO2 Laser Research Articles

Laser applications in arts and culture: An example on the construction of tiered umbrellas

Tiered umbrella or in Thai called Chat means a high decoration or decoration of honor, a type of umbrella that is stacked up in layers along a single axis. At present, in Thailand, the tiered umbrellas are seen in three important places including (1) on the top of the pagoda of various temples, (2) inside the ordination hall of temples, and (3) inside the Grand Palace for the king and the royal family. In the past, a tiered umbrella was made from brass because its color was similar to gold. Constructing each set of tiered umbrellas requires a skilled technician and takes a lot of time. At present, laser cutting of metals has been widely used in the production section of the industry. This is due to the advantages of laser cutting that include narrow kerf width, smooth cutting edges, high cutting speed, reduced material waste, no tool wear, and easy automation and manipulation even for complex shapes. In this work, an example for the construction of seven-tiered umbrellas from stainless steel sheets using a high-power CO2 laser was reported. The results show that the total working time for the construction of a seven-tiered umbrella is about 113 h, which is much less time compared to 3–6 months taken by craftsmen. Therefore, this method can preserve the construction of tiered umbrellas in Thailand even though craftsmen are scarce at present.

Suppressing effect of shortening vapor cell stem on polarization-induced magnetic gradient relaxation of Xe in NMR co-magnetometers

The Rb polarization-induced magnetic field gradient is one of the crucial sources of Xe spin relaxation in NMR co-magnetometers. The additional volume of the atomic vapor cell stem can enhance the effective magnetic field gradient through the diffusion effect of the optically polarized-Rb atoms, which affects the spin relaxation properties of Xe and degrades the long-term stability of NMR co-magnetometers. Based on the discrete steps random walk diffusion model, the magnetic gradient relaxation properties of Xe diffusing in an asymmetric cell composed of a cubic part and a cylindrical tube (stem) are characterized. Simulation results indicate that a shorter stem can effectively prolong the nuclear spin relaxation time under a constant magnetic field gradient. To verify this conclusion, a cell stem truncating actuator is developed using a high-power CO2 laser to shorten the cell stem, and the magnetic field gradient coil is used to perform the gradient compensation to examine the impact of various stem lengths on the spin relaxation rate. Experiments indicate that under the influence of atomic diffusive motions, shortening the stem length can effectively suppress the polarization-induced magnetic gradient and increase the 129Xe transverse relaxation time from 4.5 s to 21 s. The study posts practical applications for vapor cells with a stem, which is expected to enhance the performance of atomic spin co-magnetometers.

Flexible and freestanding temperature sensors based on laser carbonization of carbon nanofibers

A new single-step, low-cost method for producing a wearable, flexible temperature sensor has been developed using laser writing technology. The process involves carbonizing and patterning polymeric nanofibers to create a standalone laser-carbonized nanofibers (LCNFs) substrate. A large-area polyacrylonitrile nanofibers mat is first prepared using electrospinning and then carbonized with a high-power CO2 laser beam. The resulting LCNFs are highly conductive and retain their fibrous structure. The near-complete disappearance of polyacrylonitrile peaks in the FTIR measurements and the high-intensity characteristic peaks of carbon materials obtained in the Raman scattering measurements of the LCNFs confirm their complete carbonization. SEM microscopy showed that the fibrous structure of the LCNFs remained intact after the laser carbonization process with no significant damage. Additionally, TEM microscopy revealed that the LCNFs are made up of axially ordered graphene sheets, which form their unique fibrous structure. LCNFs' temperature sensor exhibits >87% higher temperature coefficient of resistance (TCR) than laser-induced graphene (LIG) temperature sensor on a polyamide substrate when tested under the same experimental conditions. The LCNFs sensor also boasts excellent resistance stability, mechanical stability, and flexibility. To fit various wearable applications and enhance the temperature-sensing capabilities, three different sensor patterns of LCNFs were created: square, serpentine, and heater. Among these patterns, the heater design exhibited superior TCR and temperature response. However, it also had a higher thermal mass compared to the other patterns.

Enhancing Methyl Orange Degradation with Laser-Generated ZnO and Ce-Doped ZnO Nanoparticles

The presence of Methyl Orange, a hazardous organic compound typically found in industrial wastewater, presents a significant environmental challenge, necessitating the development of effective strategies for its removal to mitigate adverse impacts on aquatic ecosystems and human health. In this work, we utilized 60-watt continuous-wave (CW) and high-power CO2 laser with 10.6 μm wavelength to synthesize Zinc Oxide nanoparticles (ZnO NPs) doped with 1% Cerium (Ce) as photocatalyst at standard laboratory conditions through Laser-Assisted Chemical Bath Synthesis (LACBS) technique. The synthesized nanostructures were thoroughly characterized using UV–vis spectroscopy, field-emission scanning electron microscopy (FESEM), and X-ray diffraction (XRD) techniques. Subsequently, their efficiency in degrading Methyl Orange (MO) dye was evaluated under UV and sunlight irradiation. The findings revealed that the 1% Ce-doped ZnO sample exhibited enhanced photocatalytic efficiency under both UV and sunlight irradiation, as well as active adsorption capabilities in the absence of light. Notably, the most effective photodegradation performance was achieved under solar radiation, with an impressive 95% of MO dye degradation observed after just 90 min of exposure.

Laser-induced carbonization of carbon nanofibers free-standing electrodes for flexible interdigitated micro-supercapacitors

A versatile one-step laser writing technique is introduced in this work for carbonizing and patterning polymeric nanofibers mat to produce a free-standing laser carbonized nanofibers (LCNFs) electrode for flexible interdigitated microsupercapacitors. A large-area polyacrylonitrile nanofibers mat was first prepared with the facile electrospinning technique on a collecting drum followed by a stabilizing step. A high-power CO2 laser beam is used to carbonize the stabilized nanofibers into highly conductive LCNFs at ambient atmospheric conditions and draw the interdigitated pattern at the same time. The complete carbonization of the nanofibers is confirmed by the nearly complete disappearance of polyacrylonitrile peaks in the FTIR measurements and from the high-intensity characteristic peaks of carbon materials obtained in the Raman scattering measurements of the LCNFs. The SEM microscopy showed that the LCNFs were able to survive their fibrous structure after the laser carbonization process and without any significant damage. Also, the TEM microscopy revealed that the LCNFs are composed of graphene sheets that are axially ordered to form such a unique fibrous structure. Owing to its outstanding structural and electrical properties, the LCNFs interdigitated supercapacitor attained an aerial specific capacitance of 20.38 mF/cm2, a high energy density of 0.64 μWh/cm2, and a high-power density of 224.6 μW/cm2 which are almost two-fold higher than those of the laser-induced graphene (LIG) on a polyamide substrate assembled with the same conditions. This was accompanied by an excellent capacitance retention of 95.3 % after 10,000 electrochemical cyclic stability and impressive mechanical stability and flexibility.

Laser melting manufacturing of large elements of lunar regolith simulant for paving on the Moon

The next steps for the expansion of the human presence in the solar system will be taken on the Moon. However, due to the low lunar gravity, the suspended dust generated when lunar rovers move across the lunar soil is a significant risk for lunar missions as it can affect the systems of the exploration vehicles. One solution to mitigate this problem is the construction of roads and landing pads on the Moon. In addition, to increase the sustainability of future lunar missions, in-situ resource utilization (ISRU) techniques must be developed. In this paper, the use of concentrated light for paving on the Moon by melting the lunar regolith is investigated. As a substitute of the concentrated sunlight, a high-power CO2 laser is used in the experiments. With this set-up, a maximum laser spot diameter of 100 mm can be achieved, which translates in high thicknesses of the consolidated layers. Furthermore, the lunar regolith simulant EAC-1A is used as a substitute of the actual lunar soil. At the end of the study, large samples (approximately 250 × 250 mm) with interlocking capabilities were fabricated by melting the lunar simulant with the laser directly on the powder bed. Large areas of lunar soil can be covered with these samples and serve as roads and landing pads, decreasing the propagation of lunar dust. These manufactured samples were analysed regarding their mineralogical composition, internal structure and mechanical properties.

A Promising Crystalline KCl: Electrolyte Material for Studying the Electrochemical Properties of Cerium on Liquid Indium Electrodes

Potassium chloride crystals are good conductors in the UV to mid-infrared broadband and can be widely used as materials for high-power CO2 lasers. However, the most important use of potassium chloride crystals has been overlooked; their stable chemistry and wide electrochemical window allow them to form molten eutectic salts with other chlorides for the dry reprocessing of spent fuel. The aim of this work is to investigate the electrochemical properties of the actinide substitute cerium metal on liquid indium media in order to provide basic data for further realization of lanthanides (Ln)/actinides (An) separation. In this paper, we investigated the electrochemical behavior of 3LiCl-2KCl-CeCl3 melt at liquid metal media indium (In) electrode using various transient electrochemical analysis methods, such as cyclic voltammetry, square wave voltammetry and open circuit potential technique. The quasi-equilibrium potentials of Ce3+ at different temperatures on the liquid metal In electrode were determined. On the redox process, the reaction kinetics of the oxidation–reduction process in the 3LiCl-2KCl-CeCl3 system is studied. It was determined that the reduction of Ce3+ at the liquid metal In electrode is an irreversible single-step process with three electron transfers. The relationship between the diffusion coefficient and the reduction process of Ce3+ ions on liquid metal indium electrodes at different temperatures was determined. The expression for the diffusion coefficient and temperature of Ce3+ at the liquid metal indium electrode is: lnD = 1.43 − 7974.69/T.

Influence of heat input on intermetallic formation in dissimilar autogenous laser welding between Inconel 718 and AISI 316L steel

Intermetallic formation during dissimilar welding of Inconel and stainless steel significantly hinders producing sound-quality weld. In the present work, a high-power CO2 laser welding system is employed to join Inconel 718 and AISI 316L stainless steel without using any filler materials. The finite element based thermal model provides the temperature distribution in the weld zone and consequently the solidification parameters (G/R and G.R). The micro-segregation and intermetallic formation in laser welding are correlated with these solidification parameters. The segregation of principal alloying elements triggers the formation of intermetallic phases during solidification. The presence of various phases like Laves, NbC, and TiC in the fusion zone reduces with increase in heat input. The amount of these intermetallic phases present in the weld zone is estimated by XRD analysis. With an increase in heat input, the mode of solidification changes from columnar to equiaxed dendrites that is characterized at reduced value of solidification parameter (G/R). The intermetallic Laves particle diminishes significantly (more than 90%) with a reduction of G/R parameter. In equiaxed dendrites, the segregation and formation of these secondary particles reduces to more than 40% compared to the columnar dendritic structure. Overall, the reduction in the intermetallic particles improves the joint efficiency up to 100% with an elongation of 14.2% for the equiaxed structure of the laser welding system.

CA single track simulation of laser conduction welding with stainless steel 316L (1.4404)

The study presents a coupled cellular automata (CA) approach for a single track microstructure simulation for laser conduction welding. A high-power CO2 laser beam (1000 W) traverses the substrate, with the beam shaped by conventional optics, which produces a Gaussian profile. The process parameters produce a shallow melt phase maintaining a conduction limited weld seam. The stainless steel material 1.4404 was used as substrate material with a grain size of approximately 20 µm without any filler material. The cooling rates and initial grain size influence the grain morphology and were determined. The size of a single crystal was simulated for different cooling rates. The simulation outputs of the melt pool boundary are qualitatively and quantitatively compared to experimental results. The micrograph results have shown that fine sub cells are developed. This fine cellular microstructure was only satisfactorily resolved experimentally along the melt pool boundary. The simulation results are in acceptable agreement with the experiments at the melt pool boundary. They match in terms of cooling rate, grain angle, and primary dendrite spacing. However, the simulated grains are longer which indicates the necessity of homogenous nucleation in the liquid melt pool.

Effect of CO2 Laser Fluence in Cladding Process on the Microstructure of Cold Rolled 0.2 % Carbon Steel

In this article a 1.8kW continuous wave of high power CO2 laser was used to clad of a titular composition of Ni – 10 wt% Al powder on cold rolled 0.2% carbon steel substrate. The feed rate was kept constant after many preliminary claddings at approximately 11 g/min. In order to produce clads with different specific energies and interaction times, different traverse speeds were used in the range of 1.5 to 12.5 mm/s. The microstructure of substrate was changed at the heat affected zones under the variety of specific energies. The cladded coatings showed the presence of ɣ solid solution and β (NiAlFe) phases. A strong metallurgical bonding produced between the substrate and the clad coat at fluence higher than 48 J/mm2. The changing in microstructure were observed using both microscope and SEM. The microhardness was evaluated using Vickerʼs microhardness test. The microstructure of the substrate was ferrite and pearlite transformed to martensite at the region adjacent to the clad interface. It followed by a three regions can be classified, a grain growth zone (large grains of austenite/ferrite and pearlite), recrystallization zone (fine grains of austenite/ferrite and pearlite) and recovery zone (the structure has a little changes from the structure of low carbon steel). The microhardness testing result showed higher values for the clad regions compared with substrate. This study emphasize the possibility to develop a temporary new graded material.

Determining optimal laser-beam cutting equipment investment through a robust optimization modeling approach.

The acquisition of Advanced Manufacturing Technologies (AMT), such as high-power fiber or CO2 laser cutting equipment, generally involves high investment levels. Its payback period is usually more extended, and there is a moderate-to-high risk involved in adopting these technologies. In this work, we present a robust model that optimizes equipment investing decisions, considers the process’s technical constraint and finds an optimal production plan based on the available machinery. We propose a linear investment model based on historical demand information and take physical process parameters for a LASER cutting equipment, such as cutting speed and gas consumption. The model is then transformed into a robust optimization model which considers demand uncertainty. Second, we determine the optimal production plan based on the results of the robust optimization model and assuming that demand follows a normal distribution. As a case study, we decided on the investment and productive plan for a company that offers Laser-Beam Cutting (LBC) services. The case study validates the effectiveness of the proposed model and proves the robustness of the solution. For this specific application of the model, results showed that the optimal robust solution could increase the company’s expected profits by 6.4%.

Parameterized multipoint-line analytical modeling of a mobile heat source for thermal field prediction in laser beam welding

The thermal effects of the “keyhole” full penetration welding mode, which is characteristic of high-power CO2 laser, are simulated introducing a multipoint-line thermal source model based on heat conduction, parameterized by the distribution of the laser beam power, and the setting of the source system layout, and to be fitted on experimentally detected cross sections of the heat-affected or fusion zones of the weld. The proposed model allows to express the thermal field according to the moving reference system fixed on the overall heat source, and to analyze the temperature profiles that develop in some detection points fixed on the workpiece, as time varies during the welding process. By this way, it can be useful in evaluating the thermal effects that result from the variation of the main welding parameters (beam power, welding speed, plate thickness), with the aim of simplifying the selection of the optimal process conditions. As an application, reference is made to a cross section of a joint between plates of AISI 304 L austenitic steel. The fitting procedure allows to set the power distribution and layout parameters of the most suitable source combination (obtained by superposition of a line and two point sources). The value of the absorption coefficient also is assumed as fitting variable, so to overcome the complex problem of evaluating the beam power actually absorbed by the material on keyhole mode welding. Finally, the fitted model is applied to carry out a detailed thermal field analysis in the welded plates.

Effect of cutting conditions on surface roughness of machined parts in CO2 laser cutting of pure titanium

Abstract Titanium (Ti) and its alloys machining has been a long standing issue in the manufacturing industry. The extraordinary Ti machining costs restrict its used in the specialised applications. To achieve improved surface quality, researchers are working tirelessly to optimize various cutting parameters. In this study, high-power CO2 laser cutting of the 2 mm thick sheet of pure Ti is investigated. Additionally, effect of the input laser conditions on the machine surface quality is also analysed. The arithmetic roughness Ra and total roughness Rt of the cut work-pieces, produced by different cutting speed (V), laser power (Pu) and gas pressure (p) are measured by the roughness tester. The machined or cut surfaces were analyzed at several locations along the cutting surface. The Taguchi method was applied to minimize the surface roughness of the cut parts and to optimize the cutting parameters. It was observed that surfaces roughness increases with the evolution of the thermal energy by laser power. However, surface roughness decreases with faster cutting speeds. Finally, the optimum cutting conditions for the arithmetic roughness (Ra) was recorded at laser power Pu of 2 kW, V of 2400 mm/min and p of 14 bars. For total roughness (Rt), Pu, V and p were 2 kW, 2400 mm/min and 2 bars respectively.

Microstructure and Properties of Inconel 625 Fabricated Using Two Types of Laser Metal Deposition Methods.

The effect of using two different deposition systems on the microstructure and mechanical properties was studied in this paper. For this purpose, laser-engineered net shaping (LENS) and high-power CO2 laser deposition processes were applied to fabricate Inconel 625 samples. The microstructure of the Inconel 625 produced by both additive techniques was characterized using light microscopy (LM), scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), and transmission electron microscopy (TEM). The mechanical properties were characterized by tensile tests and microhardness measurements. High-power laser application resulted in a strong <100> build texture, while, at low powers, the {011} <100> Goss component increased. Both types of deposited materials showed dendritic microstructures with Ti-, Mo-, and Nb-rich zones at the cell boundaries, where numerous precipitates (Nb2C, NbC, titanium carbides, Nb3Ni, and NbNiCr) were also observed. It was also noted that both variants were characterized by the same slope with a proportional length, but the Inconel 625 fabricated via LENS showed a higher average yield strength (YS; 524 MPa vs. 472 MPa) and ultimate tensile strength (UTS; 944 MPa vs. 868 MPa) and lower elongation (35% vs. 42%) than samples obtained with the high-power CO2 laser deposition process.

Combined Windows for High-Power Gas Lasers

Based on a previously developed mathematical model describing the behavior of the window of a multi-kilowatt laser with an unstable cavity, the case of a two-component output window is considered. The two-component window consists of a transparent annular polycrystalline diamond and a central opaque area, separated by a plastic vacuum gasket. To reduce the heat load, the central opaque part is equipped with a cooler. Numerical calculations of thermomechanical processes for such windows used in high-power CO2 lasers are carried out. The mathematical model used for the calculations consists of three parts: thermophysical, mechanical, and optical. The advantages of the two-component design with a cooler being used with a multi-kilowatt gas laser are demonstrated. The dependences of the maximum admissible output radiation power, temperature distribution, and mechanical stresses on the window thickness are obtained. Conditions under which such an output window should not only successfully withstand the extreme radiation loads, but also ensure the minimum possible divergence of the outgoing radiation are considered.

Experimental study of laser pyrolysis of coal and residual oil

A lab-scale laser pyrolysis platform was set up to study the pyrolysis of coal and residual oil to light gases combining high accuracy, good repeatability and ultra-high temperature, fast heating rate. With a high-power CW CO2 laser used as heat source, the laser pyrolysis took place as a procedure-controlled reaction process connected with a specially designed GC to analyze the gas products on line. The temperature of samples was measured by a two-color infrared pyrometer in milliseconds time-step, and the measured ultimate temperature and heating rate exceeded 2900 K and 3 × 104 K/s respectively. Through a series of experiments, the accuracy and reliability of the laser pyrolysis platform are verified and the effects of sample weight, environmental atmosphere, laser irradiation time and power, hydrogen content in atmosphere on the yields of gas products were investigated. The appropriate operating conditions are: the weight of residual oil less than 1.0 mg, the laser irradiation time longer than 3.0 s, laser irradiation power stronger than 90 W. The relationship between laser pyrolysis and plasma pyrolysis processes has also been discussed in this work. This work established an efficient, easy-to-use method for the preliminary feedstock selection of plasma pyrolysis process because C1 + C2 yield from laser pyrolysis could be used as a criterion for plasma pyrolysis.

Creation of aerosolized detergent compositions for cleaning high-precision metal mirrors

We report on a studies on the possibility of extending the service life of products of non-ferrous metals by physical and chemical treatments with specially created azeotropic compositions. These studies were carried out on high-precision copper mirrors for high-power CO2 lasers, exposed during operation to different climatic influences, worsening of their operational characteristics. The results obtained in this paper can be applicable for physical and chemical cleaning of such mirrors and other high-precision parts from non-ferrous metals. The work is devoted to the creation of aerosol detergent compositions intended for use during the operation of mirrors in the field climatic conditions. It is shown that when aluminium and tin-plate aerosol containers are used, compositions that are used to clean metal mirrors should not contain chlorine-substituted hydrocarbons or even “traces” of water and hydroxyl ions. In addition to copper mirrors, optical elements made of other materials were also studied in this work.

Surface Quality of Ti-6Al-4V Titanium Alloy Parts Machined by Laser Cutting

This paper investigates high power CO2 laser cutting of 5mm-thick Ti-6Al-4V titanium alloy sheets, aiming to evaluate the effects of various laser cutting parameters on surface roughness. Using multiple linear regression, a mathematical model based on experimental data was proposed to predict the maximum height of the surface Sz as a function of two laser cutting parameters, namely cutting speed and assist-gas pressure. The adequacy of the proposed model was validated by Analysis Of Variance (ANOVA). Experimental data were compared with the model’s data to verify the capacity of the proposed model. The results indicated that for fixed laser power, cutting speed is the predominant cutting parameter that affects the maximum height of surface roughness.

Study on microstructure and mechanical properties of Ni60 + WC/Ni35/AISI1040 functional surface gradient structure of remanufacturing chute plate for the mining scraper by a low cost high power CO2 laser cladding technique

CO2 laser cladding is a type of green remanufacturing technology, which is of many technical advantages in repairing and remanufacturing industry, especially for some large-scale key mining equipment or parts due to its characteristics of high quality, high efficiency and environmental protection (e.g. energy and material saving). In this paper, the chute plate of coal mining scraper is fixed and remanufactured by CO2 laser cladding technique. Ni60, WC, Ni35, IG55 and other composite powders are selected to design and build the gradient functional structure for chute plate in order to improve the reproduced lifetime. A lot of high power low cost CO2 laser cladding tests are carried out on the matrix material (AISI 1040 steel plate) of old attrite chute plate. The optical microscope, SEM, XRD, microhardness test and wear experiment are adopted to analyze the relationships among the laser cladding process, the overlaying composite material, gradient functional structure and mechanical properties of the remanufacturing scraper’s chute plate. The research results show that laser power and scanning speed are the dominant cladding process parameters, which have a significant influence on the geometric dimension (including width and height), dilution rate and hardness of the deposited layer. These composite powders (especially including the rare earth metals) are the key factor to form the gradient functional structure. The laser cladding Ni60 + WC/Ni35/AISI1040 composite gradient functional structure has a reasonable toughness and strength of the transition layer structure, and a high hardness and wear-resistant surface functional layer, so the fixed and remanufactured product has formed good ductile plasticity and wear resistance properties as a result of the gradient functional structure. The unique Ni60 + WC/Ni35/AISI1040 gradient functional structure makes sure that the chute plate of mining scraper has excellent comprehensive performance, which is satisfied with the service requirements of mechanical parts or equipment in the harsh working environment of the mining industry. This research work provides technological guidance for the fix and remanufacturing chute plate, and achieves the goal of low cost, high efficiency and long life reproduced chute plate of mining scraper.

Комбинированные окна для газовых лазеров высокой мощности

Based on the previously developed mathematical model of the behavior of the multi-kilowatt laser window with an unstable cavity, the case of a two-component output window is considered. The two-component window consists of a transparent polycrystalline diamond ring and a central opaque area separated by a plastic vacuum gasket. The central opaque area is equipped with a cryoaccumulator to reduce heat load. Numerical calculations of thermomechanical processes are performed for such windows used in high-power CO2 lasers. Mathematical model used for the calculations consists of three parts - thermophysical, mechanical and optical. The advantages of using a two-component design with a cryoaccumulator under the conditions of a gas laser operating in the multi-kilowatt power range are demonstrated. The dependences of the maximum output power, temperature distribution and mechanical stresses versus the thickness of the window are obtained. The optimal conditions providing maximum radiation strength and minimum beam divergence are considered.