Effect Of Laser Parameters Research Articles

Picosecond laser-induced evolution of processing properties of 4H–SiC

The irradiation threshold of 4H–SiC under picosecond laser action was calculated, and the influence of laser parameters on the size of 4H–SiC was studied. According to the model, the evolution rule of the microgroove size was predicted. The effect of laser parameters on the mechanical properties of 4H–SiC was studied by nanoindentation. The results show that the ablation threshold energy density of the picosecond laser on 4H–SiC is 2.67 J/cm2. The effect regular of laser parameters on the size of 4H–SiC microgrooves: energy density > scanning speed > scanning interval. The error of the microgroove which is between the predicted value and measurements is within 10 %. By doing nanoindentation detection, proving that Pop-in is the elastic-plastic transition point. It shows that laser irradiation has a significant modification effect on the mechanical properties of 4H–SiC. According to the difference range of elastic modulus and hardness, showing that the influence of laser energy density on mechanical properties is dominant. The consequences of the study provide a theoretical foundation for subsequent CMP processing.

Influence of laser parameters on the machining performance of textured cutting tools

Over the past three decades, surface texturing has garnered significant interest as a method of controlling friction and wear in tribological systems. Surface textures play a significant role in reducing friction under dry machining conditions by lowering adhesion, decreasing the effective area of contact, and collecting wear particles. However, the effect of various laser parameters on the machining performance of textured tools is still unclear. In this research study, linear textures have been fabricated on the rake surface of uncoated carbide tools using the Nd:YAG laser by varying the laser parameters. The effect of the laser parameters, such as fluence and the average number of pulses per surface spot has been evaluated in terms of depth of textures, resolidified layer, and change in substrate hardness. The textured tools have been further used for turning the pH 13–8 Mo SS (UNS S13800) alloy under dry and wet conditions. The machining outcome results obtained with the textured tools have been compared with the plain tool. The turning experiments showed that textured tools helped in improving the machining performance by reducing the cutting forces, cutting temperature, surface roughness, and tool wear. In this research work, the textured tools fabricated with the combination of fluence = 31.4 J/cm2 and pulses per surface spot = 5 pulses/surface spot have outperformed the other textured tools fabricated with the combination of different laser parameters in terms of machining performance.

Preparation and characterization of germanium dioxide nanostructure for gas sensor application: effect of laser parameters

In this article, a novel application of germanium dioxide (GeO2) as a gas sensor is systematically reported. In detail, GeO2 layers were deposited on quartz and n-type Si substrates, as a function of laser pulses, using combined laser ablation and thermal spray coating approaches. The attained layer/s were methodically inspected in term of their morphological, structural, and optical features; specifically, highly crystalline GeO2 structure was obtained for samples prepared using 1500 pulses and above. In the meanwhile, the obtained particle diameters were found to be within the range of 15 to 274 nm, while the estimated optical band gaps exhibited values from 3.85 to 4.0 eV. Simultaneously, the gas sensing behavior demonstrated a well-oriented performance for all devices, however, devices treated with 2500 pulses delivered stable trend with sensitivity value as high as 3 × 10−6. The rise/fall period revealed an adequate outcome (~10 𝑠𝑠𝑠𝑠𝑠𝑠.) for gas sensors fabricated via pulses of 1000 and above, with respected to the working temperature. The proposed framework delivers a substitute technique towards 2D metal oxide based eco-friendly-gas sensor.

Femtosecond laser printing-assisted etching tailored hard and brittle micro-convex surface.

We report a femtosecond laser print-assisted dry etching technology for high-efficiency, high-quality, and tailored fabricating of a micro-convex surface (MCS) on hard and brittle materials. Liquid ultraviolet curing adhesive (UVCA) was transferred from a donor substrate to a receiving substrate by femtosecond laser-induced forward transfer, and the transferred microdroplet spontaneously has a smooth surface under the action of surface tension. And then an MCS with a high-quality surface was formed on hard and brittle materials by UV curing and dry etching. The effects of laser parameters and receiving substrate surface free energy on MCS morphology were investigated. According to the variation of the numerical aperture, the two methods to change the morphology of the MCS were divided into independent/joint regulation of diameter and height. We showed that a hexagonal array containing a variety of MCS morphologies can be fabricated on a fused silica by setting the appropriate parameters. And the fabrication time of an MCS in a large-area array was only 1.1s.

In-situ synthesis of TiC/Ti alloyed layer via pulsed Nd:YAG laser melting of Ti-6Al-4V titanium with preplaced carbon-based powder

The present research deals with fabricating an in-situ TiC/Ti alloyed layer on the Ti-6Al-4V titanium alloy through the preplacement of a mixture of graphite and nickel powders and subsequent pulsed Nd:YAG laser melting. The comprehensive effects of laser parameters, including scanning speed and energy density on the microstructural evolutions and hardness variations were investigated. It was found that the geometry of treated layers varied from 150 to 200 µm in thickness and 1200–1750 µm in width depending on the thickness of the preplaced layer and laser peak power. The promising results of X-ray diffraction patterns and scanning electron microscope observations manifested the formation of in-situ TiC and an increase in its content versus the energy density of the laser beam. The main mechanism of the in-situ formation of TiC in the matrix during laser irradiation was also discussed. The results indicated that the in-situ TiC phases had either dendritic or needle-like morphology. Laser parameters were crucial in establishing the TiC morphologies associated with temperature and chemical composition. The hardness values of the fabricated layers were directly proportional to the amount of TiC in the treated layers and varied from 1000 to 1400 HV0.3, which was nearly 3–4 times higher than that of the substrate.

Laser cutting of basalt fibre reinforced polymers by QCW fiber laser: Interaction mechanisms and effect of laser parameters

In the paper, laser cutting of basalt fibre reinforced polymer laminate using a 450 W QCW fiber laser, working in a pulsed regime is presented. Preliminary tests were performed on a basalt laminate, 1.3 mm in thickness, changing the pulse power (Pp) and pulse duration (D) to find the maximum cutting speed. Then a 33 experimental plan was carried out changing the pulse power, the pulse duration, and the cutting speed. The kerf width and the heat-affected zone were measured in the section and on the external surfaces. ANOVA analysis was adopted to assess the process parameters’ influence. The interaction mechanisms were found and discussed. From the results, the BFRP laminate appears easy to cut at maximum cutting speeds up to 3500 mm/min. However, thermal damages occur. Kerf geometry and HAZ are mainly affected by the cutting speed, while the Pp and D seem to have a minor role.

Effect of nanosecond pulsed laser parameters on texturing formation of metallic surface: Experiment and modelling

The laser ablation process is an indispensable tool in precision micromachining for fabricating micro/nanostructures with specific geometries and regulating physicochemical properties on target surfaces. However, the absence of studies on the effect of laser parameters on texturing formation and surface microstructure makes process control and the optimization of surface texturing challenging. In this study, a nanosecond pulsed laser process was employed to create the micro-texturing on the Al alloy surface, emphasizing the effect of process parameters on surficial grain structures and texturing formation. A three-dimensional (3D) heat transfer model based on the finite element (FE) method was developed to numerically visualize the shape-dimensional evolution of micro-texturing during laser ablation. A simplified but effective moving laser heat source model was proposed to predict the dynamic spatial and temporal distributions of heat generation and transfer. Material removal, which was dominated by surface evaporation in the pulsed laser process, was achieved using the element deletion method. Under various laser parameters, the model-predicted cross-sectional groove profiles agreed well with experimental measurements. In addition, the effects of laser power and scanning speed on the groove morphologies were investigated. The experimental findings and numerical models established in this study will provide guidance for precisely controlling pulsed laser parameters to achieve desired texturing structures and dimensions.

Grain visualization of FeCoCrMnNi and AlCoCrFeNi2.1 high-entropy alloys by nanosecond pulse laser irradiation

Characterizing grains is the most common method in materials science research, but the existing techniques for grain characterization are generally expensive and time-consuming. In this study, nanosecond pulse laser irradiation with low laser fluence is attempted to visualize the grains of two typical high-entropy alloys (HEAs) with different crystal structures and elemental compositions. The effects of laser parameters and gas atmospheres on the laser visualization of grains are comparatively investigated. Under specific laser irradiation conditions, the grains of these two HEAs could be well visualized by producing different surface nanostructures. By experiments and analysis, the underlying mechanisms of laser visualization of grains under different conditions are elucidated, and the role of O element on the promotion of the visualization of grain boundaries is confirmed. This study provides a simple and efficient method to visualize the grains of HEAs, and on the other hand, enhances the understanding of nanosecond laser-HEA interaction.

Laser shock forming of metal nanostructures withultrafine gaps.

The nanogaps between metal nanostructures are of great importance in nanotechnology. However, low cost and high precision fabrication of such nanogaps is still a difficult problem. In this paper, a method combining nanosecond laser shock and flexible metal film is proposed to form ultrafine gaps between metal nanostructures. The forming mechanism of ultrafine gaps between metal nanostructures was revealed by studying the superplastic deformation, spatiotemporal evolution of stress and strain, and cooperative deformation of the flexible metal thin film and metal nanostructures under laser shock. On the basis of the mechanism study, the effects of laser parameters and gold nanoparticle size on the forming of ultrafine gaps were further studied, so as to achieve high precision forming of ultrafine gaps (<10n m) between metal nanostructures.

Fabrication of Ohmic Contact on N-Type SiC by Laser Annealed Process: A Review

In recent years, because of stringent needs in the fabrication of silicon carbide (SiC) power devices, laser annealing has been introduced to achieve local ohmic contact. In this paper, the laser annealing research for the ohmic contact process of SiC power devices is reviewed, which is mainly divided into four aspects: laser process mechanism, ohmic contact electrode materials, and substrate materials. The effect of laser parameters on ohmic contact and the annealing process on SiC diode devices is also reviewed. Progress of other substrate materials, namely 6H-SiC and semi-insulating 4H-SiC-based devices with laser annealed ohmic contacts, is also briefly discussed, in which formation of semi-insulating SiC ohmic contacts is derived from laser irradiation at the interface to produce 3C-SiC. Some experiment results have been shown in the passage, such as XRD, SEM, TEM, etc. In the review, it points out that the direction of application and development of the laser annealing process for improving the ohmic contact of SiC power devices is highly encouraging.

Optimization design of laser-EMAT and its application in high-temperature forgings detection

In high-temperature continuous forging process, according to the real-time monitoring of workpiece thickness and flaws, the processing parameters can be adjusted accordingly, so we can remove defective components in time, which has essential research value for avoiding the interruption of production line and improving their yield and quality grade. We established a finite element (FE) model of the carbon steel’s laser-electromagnetic acoustic transducer (laser-EMAT) testing process. Based on the simulation model, we analyzed the effects of laser parameters, EMAT parameters, and sample thickness on the detected ultrasonic signal amplitude, and we also achieved the optimized Laser-EMAT design parameters. Subsequently, we developed a high-temperature resistant spiral coil EMAT and measured the high-temperature forging with a thickness of 100 mm and temperatures from 300 °C to 730 °C. Based on the experiments, we researched the effect of specimen temperature on the received ultrasonic wave amplitude. The results show that the excitation efficiency of laser-induced ultrasonic waves improves by decreasing pulse duration, decreasing laser spot radius, and increasing pulse laser energy. The receiving efficiency of the shear wave (SW) detected by the EMAT enhances when reducing the diameter of the EMAT wire and increasing the permanent magnet height. When the radius of the permanent magnet is equal to the radius of the EMAT coil, the receiving efficiency of SW is the highest. As the sample thickness increases, the size of the EMAT should increase accordingly to the acoustic beam divergence for obtaining a higher ultrasonic wave intensity. The amplitude of the SW signal received by the EMAT increases by 679% after the optimization design. With rising carbon steel forging temperature, the SW signal amplitude increases first and then decreases sharply, reaching its maximum at 617 °C, which is 29% higher than at room temperature, and the signal-to-noise ratio (SNR) of the SW is 20.5 dB.

High compressive plasticity refractory medium entropy alloy fabricated by laser powder bed fusion using elemental blended powders

High plasticity light weight refractory complex concentrated alloys (RCCAs) are the best alternative to replace nickel base alloy. The advantages of additive manufacturing (AM) in the rapid and direct forming of complex structure RCCA parts are beyond the reach of traditional techniques. In this work, a simple composition of refractory metal elementals was carefully designed. The single-phase BCC Nb–40Ti–20Ta refractory alloy was fabricated by laser powder bed fusion (LPBF) using elemental blended powders, it has excellent compression plasticity (e>80%) and strength at both room and high temperatures. The effects of laser parameters and treatment process on microstructure and mechanical properties of the Nb–40Ti–20Ta alloy were investigated. The experimental results show that the density and hardness of the alloy are approximately positively correlated with the laser energy density. The laser parameters have a significant effect on the microstructure. Too low energy density leads to the formation of some unmelted powders, while too high power density results in the transformation of micro-pore into larger keyhole. The laser short action time and too rapid cooling rate of the molten pool induce the micro-segregation in grains. β-phase dendrites are formed from inside to outside while the high melting point Ta acts as the center, and Ti is enriched in the inter-dendrite region. The shapes of grains are divided into two types: columnar and cellular substructures. The single phase BCC Nb–40Ti–20Ta alloy has ultra compressive plasticity whether annealed or not. The results show that the novel alloy prepared by LPBF possesses excellent mechanical properties. This work provides an important progress for the preparation high compressive plasticity RHEAs by LPBF using elemental blended powders.

Generalized thermoelasticity study in ultrashort pulsed laser machining of ceramic considering material removal and variable material properties

Ceramic materials are widely used in engineering due to their excellent properties, but they are difficult to be machined by conventional techniques. Ultrashort pulsed laser is an applicable tool to achieve high-quality processing of these hard-brittle materials. However, the ultrashort thermalization time and complex interactions in laser processing bring great difficulty to describe thermal-mechanical responses precisely. For this purpose, we establish a model for ceramics irradiated by femtosecond pulsed laser in the context of Green-Lindsay generalized thermoelastic theory, considering the effect of material removal and temperature-dependent material properties. Thermoelastic responses and the effect of laser parameters in the machining considering material removal are obtained by means of Finite Element Method. Results show that classical thermoelastic theory underestimates thermal stresses, while G-L thermoelastic theory predicts more accurate responses. Laser parameters, including laser intensity and pulse duration, significantly affect the thermoelastic responses and the process of material removal, which indicates the necessity of laser parameter optimization for reduced thermal stresses and higher processing efficiency. Temperature-dependence of material properties must be considered, as it has pronounced influences on thermoelastic responses. This study can be used as the preparation for the structural safety design in ultrashort pulsed laser machining.

Laser parameters affecting the asymmetric radiation of the electron in tightly focused intense laser pulses

The nonlinear radiation of the electron is a distinctive feature of the action of tightly focused linearly polarized lasers. In this paper, from the perspective of radiation symmetry, the effect of laser parameters on the electron radiation power in the time domain is studied systematically. An asymmetric bimodal structure is found in the time domain in the direction of the maximum radiation. For this special structure, an explanation is given based on the electron dynamics perspective. The structure is compared with the symmetric bimodal structure in the classical theory. The increase in laser intensity, while significantly increasing the radiated power of the electron, exacerbates the asymmetry of the electron radiation. The variation in the initial phase of the laser leads to a periodic variation in the electron motion, which results in a periodic extension of the electron spatial radiation with a period of π. Moreover, the existence of jump points with a phase difference of π in the range of 0–2π is found. The increase in pulse width reduces the radiated power, extends the radiation range, and alleviates the radiation asymmetry. The results in this paper contribute to the study of electron radiation characteristics in intense laser fields.

Effect of laser parameters on fatigue crack growth behavior of AZ31B magnesium alloy TIG welded bionic joint

The purpose of this study was to evaluate the effect of laser parameters on the fatigue crack growth (FCG) behavior of AZ31B Magnesium alloy TIG welded bionic joints with ‘soft-hard’ alternating structures prepared by laser bionic treatment (LBT). The changes of laser parameters promoted the growth of fine equiaxed grain with random texture, and average grain size was 5.12 ± 0.51–8.19 ± 1.02 μm, which significantly increased isotropy and microhardness. The average microhardness was 66.5 ± 1.68–70.85 ± 1.41 HV0.1, which increased by more than 23.11% compared with untreated welded joints. For bionic welded joints, the heat-affected zone (HAZ) had higher FCG resistance and cycle times than weld metal (WM), and the specimens with notch in the HAZ showed obvious crack deflection. It was found that FCG behavior showed significant microstructure sensitivity by comparing the FCG rate curve and crack opening displacement. The Paris parameters had a significant linear relationship and effectively reflect the FCG resistance of the different specimens. The fatigue fracture showed that the crack growth zone was mainly dominated by typical cleavage steps and secondary cracks. The fatigue fracture region contains quasi-cleavage and ductile fracture. A series of strengthening mechanisms were induced by LBT and could significantly affect FCG behavior, which promoted crack deflection and branching to increase the toughness of the joint, while the laser remelting zone increased the strength of the joint. Therefore, the synergistic effect of strength-toughness of the joint was obtained by LBT, which provided a new idea for optimizing the bionic design and improving the fatigue property of welded joints.

Key technologies for laser-assisted precision grinding of 3D C/C-SiC composites

Due to their exceptional and distinctive qualities, 3D C/C-SiC composites are widely utilized in producing high-end equipment and the aerospace national defense industries. However, the hard and pseudo plastic nature of the material and its anisotropies make it challenging to process. To improve the processing quality of 3D C/C-SiC composites, laser-assisted precision grinding technology is introduced in this paper, which innovatively controls the depth of the thermally induced damage layer by adjusting the laser process parameters to reduce the hard brittleness of the material, and then the surface is created by precision grinding with a grinding wheel on this basis. Experiments on laser-induced damage, laser-assisted grinding, and diamond scratching were carried out to investigate the effect of laser parameters on material damage and the effect of laser-assisted grinding processes, with an emphasis on revealing the mechanism of material removal. The results show that laser irradiation causes complex reactions such as sublimation, decomposition, and oxidation of 3D C/C-SiC composites, resulting in SiO2 and Si and recondensed SiC, causing surface/subsurface damage. A maximum reduction in normal grinding force, tangential grinding force, specific grinding energy, and surface roughness of 35.6%, 43.6%, 43.58%, and 24.22%, respectively, compared to conventional grinding processes with laser-assisted grinding. After laser irradiation, the degree of brittle fracture in the precision grinding of workpieces is significantly reduced due to the degradation of matrix and fiber damage caused by laser irradiation, which reduces the hard and pseudo plastic properties of the material. The removal mechanism shows a trend of ductile domain removal in the grinding of thermally damaged layers, which reduces the grinding force and improves the surface quality.

Investigation on the effect of laser parameters and hatch patterns on the dimensional accuracy of micro-dimple and micro-channel texture geometries

Investigation on the effect of laser parameters and hatch patterns on the dimensional accuracy of micro-dimple and micro-channel texture geometries

Optimisation of Rayleigh wave Laser-EMAT with the application of surface constraint mechanism

ABSTRACT A laser-electromagnetic acoustic transducer (Laser-EMAT) Rayleigh wave (RW) detection based on surface constraint mechanism and its optimisation design are proposed to solve the low signal-to-noise ratio (SNR) of its application in aluminium alloy detection at high-temperature. We established a finite element (FE) model of aluminium alloy’s Laser-EMAT RW detection process based on the surface constraint mechanism and investigated the effect of the surface constraint mechanism on laser-excited RW . We also studied the effects of laser parameters and meander-line coil (MLC) EMAT parameters on the ultrasonic wave amplitude and spectral composition. Finally, the enhancement effect of the surface constraint mechanism on RW amplitude was analysed by Laser-EMAT RW detection experiments on aluminium alloy at room temperature and high temperatures. The results show that the optimised MLC-EMAT can increase the RW amplitude by 1.97 times. When the laser line source width equals the MLC-EMAT turn spacing, the echo SNR is the highest. The enhancement effect of the surface constraint mechanism on the RW amplitude gradually decreasesas the specimen temperature increases. The RW amplitude can increase by 1.43 times when the surface constraint mechanism is applied at room temperature, and for the aluminium alloy specimen at 430°C, the RW amplitude can increase by 32%.

Effect of Laser Parameters on Laser-Induced Graphene Filter Fabrication and Its Performance for Desalination and Water Purification.

Laser-induced graphene (LIG) is a low-cost, chemical-free single-step fabrication process and has shown its potential in water treatment, electronics, and sensing. LIG fabrication optimization is mostly explored for dense polyimide (PI) polymers. However, LIG-based filters and membranes for water treatment need to be porous, and additional steps are required to get porous surfaces from PI-based surfaces. Polyethersulfone (PES) porous membranes are cost-effective and are common in water purification as compared to PI; further, the optimization of LIG fabrication on PES-based porous membranes is not explored. So, this study demonstrated the fabrication, optimization, and characterization of LIG with different laser parameters such as power, speed, image density (ID), focusing, laser platforms, and membrane support layer effect on porous PES commercial (UP010) and lab-casted 15% PES (PES15) membranes. The performance of optimized LIG filters was tested for interfacial evaporation (IE)-based desalination in single and stacked layer configuration and water purification applications such as dye removal and disinfection. IE was done in Joule heating (JH) and solar heating (SH) modes, and the UP010-ID7 LIG filter showed the highest JH evaporation rates of ∼1.1, 1.8, and 2.82 kg m-2 h-1 in single, double, and triple stacked configurations, respectively. Using a JH IE setup, the best-performing UP010-ID7 LIG filters have also shown ∼100% removal of methylene blue dye from the contaminated water. Furthermore, all LIG filters showed a complete 6-log bacterial inhibition at the 5 V filtration experiments; at 2.5 V, the optimized LIG filters showed a higher removal than the non-optimized filters. Additionally, the LIGs obtained with the aluminum platform were the best quality. This work demonstrates that laser power, ID, platform, and membrane support are critical parameters for the best-performing PES-LIG filters, and they can be effectively utilized to fabricate PES-based LIG porous surfaces for various energy, environmental, and catalysis applications.

A composite strategy for high-quality and high-efficiency milling of alumina ceramic via femtosecond laser burst-mode

Industrial alumina ceramics require high surface accuracy when assembled to critical components of devices, for which high-quality milling has become an integral process. To achieve high-quality milling of alumina ceramics efficiently, this paper introduced a composite strategy based on the sequence of roughing and finishing via the femtosecond laser burst-mode. Firstly, the effects of laser parameters in the single-pulse mode such as energy fluence, spot overlap ratio, and scanning spacing on the milling quality and efficiency of alumina ceramics were investigated to provide a basis of the parameter selection for the subsequent composite strategy study. Then, the influence of the burst-mode on the optimization of the milling results was discussed, and the advantages of this mode over the single-pulse mode were revealed. Finally, a comparative investigation on the processing performance between the composite strategy and the single strategy was carried out. The results showed that milling the same structure, the roughness of the groove was reduced by 10.69% compared to the optimal processing results in a single process. At the same time, the processing efficiency was maximized with an increase of 49.91%.