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Effects of single- and multi-shape laser-textured surfaces on tribological properties under dry friction
摘要： Textural morphology is an important factor influencing dry friction, and few studies have been conducted regarding the effects of single- and multi-shape textures on dry tribological properties. In this work, six types of textures including single- and multi-shape textures were produced on 40Cr steel samples by using a nanosecond laser. Reciprocating sliding tests under dry friction were conducted using a pin-on-disc friction tester. The influences of textured surfaces with different textures on tribological properties were investigated. Results showed that tribological properties were affected by different textural morphologies. The dimple-textured surface had the highest friction coefficient, followed by the groove-textured surface. The sinusoidal-textured surface had the lowest friction coefficient. The friction coefficients of multi-shape textured surfaces were lower than those of non-textured surfaces but higher than those of sinusoidal-textured surfaces. The wear properties of the tested surfaces were consistent with the friction-coefficient results. The sinusoidal- and sinusoidal–groove-textured surfaces can be considered as the optimum choices for dry reciprocating friction.
关键词： textural morphology,dry friction,tribological properties,surface texturing,Nanosecond laser processing
更新于2025-09-12 10:27:22
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Ultra-fast laser-based surface engineering of conductive thin films
摘要： Modern electronics facilitate the need for fast, efficient, and reliable methods for direct laser-based surface engineering of conductive thin film materials on flexible substrates. Recent advances in pulsed laser source development only incrementally increased the processing speeds, as those are limited by the available scanning systems. Our goal was to combine a high pulse repetition frequency high-power pulse-on-demand fiber laser source with an ultra-fast resonant scanner to achieve high throughput surface engineering. The enabling factor to compensate a resonant scanner’s sinusoidal movement were the laser’s intrinsic pulse-on-demand capabilities beyond simple pulse picking solutions. The high temporal resolution at full laser power was exploited for spatially controlled surface texturing, allowing a minimally 3 μm positioning accuracy throughout the scanner’s range at up to 60 m/s scan speed with a 10 μm laser spot size. We applied the setup to processing of ITO and metallic films on flexible substrates for touchscreens, position sensors, or EM shielding. Surface modification and patterning of the conductive layer was successfully demonstrated while keeping the underlying surface intact. We employed a simple laser ablation model in comparison to the experimental data to improve the understanding of the ablation process. The resulting surface topography was observed and analysed.
关键词： ultra-fast laser processing,resonant scanning,intrinsic pulse-on-demand,surface engineering
更新于2025-09-12 10:27:22
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In-situ full-field mapping of melt flow dynamics in laser metal additive manufacturing
摘要： Melt flow plays a critical role in laser metal additive manufacturing, yet the melt flow behavior within the melt pool has never been explicitly presented. Here, we report in-situ characterization of melt-flow dynamics in every location of the entire melt pool in laser metal additive manufacturing by populous and uniformly dispersed micro-tracers through in-situ high-resolution synchrotron x-ray imaging. The location-specific flow patterns in different regions of the melt pool are revealed and quantified under both conduction mode and depression mode. The physical processes at different locations in the melt pool are identified. The full-field melt-flow mapping approach reported here opens the way to study the detailed melt-flow dynamics under real additive manufacturing conditions. The results obtained provide crucial insights into laser additive manufacturing processes and are critical for developing reliable high-fidelity computational models.
关键词： x-ray imaging,melt flow,laser processing,powder bed fusion,Metal additive manufacturing
更新于2025-09-12 10:27:22
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Effect of Laser Processing Parameters on Surface Texture of Ti6Al4V Alloy
摘要： Surface micro-machining was performed on Ti6Al4V alloy sample by nanosecond laser. The micro-morphology, the depth of texture and the chemical composition of melt deposits were analyzed through different techniques including Ultra-Depth Microscopy, SEM and EDS. The single factor method was applied to investigate the influence of different laser parameters on the depth of texture and micro-morphology. The result showed that the depth of texture increased first and decreased with the increase of average power (11-20.9W), the texture depth decreases sharply when the scanning speed increased from 10mm/s to 40mm/s, and the repetition frequency had little effect on the depth of texture. It was possible to select an optimum combination of laser processing parameters that obtain different depths of texture without decreasing the surface quality of texture.
关键词： laser processing parameters,micro-morphology,Ti6Al4V alloy,depth of texture,surface texture
更新于2025-09-12 10:27:22
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High-resolution material structuring using ultrafast laser non-diffractive beams
摘要： Scales in the 100 nm range represent a generic cornerstone for laser material processing, enabling novel size-dependent functions on surfaces and in the bulk and thus a new range of technological applications. On these scales, the processed material acquires optical, transport or contact properties that do not only rely on local e?ects on singular topographic features but involve increasingly collective behaviors. Rapid access to sub-100 nm features with intense coherent light represents nevertheless a challenge in laser structuring in view of the optical di?raction limit. Ultrafast non-di?ractive beams with controllable time envelopes can overcome this limit and achieve super-resolved processing, a prerequisite for the next generation of ?exible and precise material processing tools. They show a remarkable capacity of structuring transparent materials with high degree of accuracy and exceptional aspect ratio. This capacity relies on triggering fast hydrodynamic and material fracture e?ects with characteristic spatial scales in the nm range. Reviewing the present achievements and technical potential, we discuss from a dynamic viewpoint the physical mechanisms enabling structural features beyond di?raction limit achieved using ultrafast Bessel beams and indicate applications of high technical relevance.
关键词： nanotechnology,non-di?ractive beams,Ultrafast lasers,laser processing
更新于2025-09-12 10:27:22
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Stiffness and hardness gradients obtained by laser surface melting of an aged β-Ti alloy
摘要： Components with variable stiffness have been attracting interest because of their potential for use in biomedical implants. Here, a β-titanium alloy aged under different conditions was subjected to laser surface melting (LSM). The high cooling rate typical of LSM avoided α-phase precipitation in the fusion zone (FZ) and heat-affected zone (HAZ) as the α precipitates were solid-solutioned into the β phase, producing a surface layer with full β phase over the aged substrate and reduced stiffness and hardness. The decrease in stiffness occurred independently of the aging condition used while the decrease in hardness was greater for the sample aged at the lower temperature as this had finer precipitates. A route involving aging at this lower temperature and LSM is proposed for use when a graded material combining a less rigid surface with the original core stiffness and strength is required, as in orthopedic implants.
关键词： Laser processing,Graded materials,Elastic modulus,Titanium alloys
更新于2025-09-12 10:27:22
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Application of combined laser processing in welding of heat-treated parts
摘要： The article deals with the questions of the end connections of heat-treated precision machine parts having a low stiffness, in particular, assembled Camshaft cars. To reduce the residual stresses that occur when welding heat-treated parts, it is proposed to perform preheating of heat-treated elements in the welding zone using a laser. Also, to reduce the deformations that may occur when welding axisymmetric structures with low stiffness, such as assembled Camshaft, it is proposed to use pulsed laser welding, and welding is performed only on the site previously processed by the previous laser. A laser machine based on two sources of laser radiation DLR-200-AC and YLR 150/1500-QCW-AC was used for experimental studies. The technological heads of lasers are coaxially arranged and have a single output lens, this allowed to calculate the processing program and the necessary laser power for the first and second laser source in a single technological window, as well as to synchronize the work of two laser sources. As samples were used assembled Camshafts, which consisted of a shaft with a Central hole, and heat-treated Cams. The shafts were made of steel 20 (WNr 1.0402), Cams of steel 40X (WNr 1.7034). Heat treatment of Cams was carried out by induction method. Analytical and technological features of processing are described. The cyclic combined process is described. The result is shown. Using the proposed methodology it is possible to use the technology of connecting axisymmetric parts with low stiffness both at the stage of analysis and modernization of existing designs, and at the stage of development of advanced designs.
关键词： welding,deformations,laser processing,residual stresses,Camshaft,heat-treated parts
更新于2025-09-12 10:27:22
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Development of BMG-B2 nanocomposite structure in HAZ during laser surface processing of ZrCuNiAlTi bulk metallic glasses
摘要： In this study, the laser scanning speed used during laser surface processing of a Zr-based bulk metallic glass (BMG) was optimised to obtain amorphous structure in the melt zone and nanocomposite structure in the heat affected zone (HAZ). For this aim, Zr65.7Ti3.3Al3.7Ni11.7Cu15.6 (wt.%) BMG foils with a 100 μm thickness were laser surface treated at the different speeds. The microstructural characteristics of the melt zone and HAZ of the different samples were studied using X-ray diffraction (XRD), differential scanning calorimetry (DSC), and high-resolution transmission electron microscope (HRTEM). Nanoindentation testing was employed to evaluate the mechanical properties. In addition, molecular dynamic (MD) simulation was used to discover the deformation mechanisms. The results showed that at a laser speed of 22.6 mm/s, the amorphous structure remained, and an improvement in mechanical properties was obtained in the HAZ. The HRTEM images revealed that in the HAZ of the optimum sample, a BMG-B2 nanocomposite structure was formed that improved the mechanical response of the HAZ, considerably. The MD results showed that the existence of B2 phase avoid stress reduction after starting of plastic deformation and even a higher stress during plastic deformation was recorded.
关键词： Laser processing,HRTEM,Zr-bases BMGs,Microstructure
更新于2025-09-12 10:27:22
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p-type doping of Ge by Al ion implantation and pulsed laser melting
摘要： Germanium recently attracted a renewed interest for its potential applications in several fields such as nanoelectronics, photonics, plasmonics, etc., but well-known issues about doping at high concentration and controlling impurity profiles prevent its integration in technology. To this purpose, p-type doping aluminum ion implantation followed by pulsed laser annealing in the melting regime has been investigated for the first time. In particular, two different regimes have been studied, in order to explore the limit of incorporation for such a method: 6.4 × 1014 Al/cm2 and 4.2 × 1015 Al/cm2, both at 25 keV, corresponding to concentrations below and above the solid solubility, respectively. We found that in the former case, oxygen contamination precludes full activation (< 60 %), as suggested by Raman characterizations. Besides, secondary ion mass spectrometry evidences pronounced out-diffusion and pile-up of the dopant near the surface. In the letter case, remarkable (～ 1 × 1020 Al/cm3), although partial (～ 30%), electrical activation is obtained, independently on O occurrence. Therefore, O-Al and Al-Al clustering are proposed as concurrent mechanisms, limiting full activation at high implanted dose. Nevertheless, the samples display good crystalline quality and, surprisingly, a significant thermal stability (up to 600° C).
关键词： Laser processing,Germanium,Doping,Ion Implantation,Aluminum
更新于2025-09-12 10:27:22
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Double line waveguide amplifiers written by femtosecond laser irradiation in rare-earth doped germanate glasses
摘要： We report the production of active double waveguides in Er/Yb doped GeO2-PbO glasses, by direct femtosecond laser writing. The glasses were produced using the melt-quenching technique and the active waveguides were written using 30 fs laser pulses, at 800 nm, with writing speed of 0.06 mm/sec and pulse energy of 32 μJ. The photo-induced negative refractive index change was of -7.4x10-3. The Er/Yb doped sample showed a relative gain (signal enhancement of 7.5 dB/cm, for 105 mW of 980 nm pump power. The relative gain compensates both, the propagation losses and the absorption losses, and a positive maximum internal gain of 4.6 dB/cm can be obtained at the signal wavelength of 1550 nm. The results obtained in present work demonstrate that Er/Yb glasses are promising materials for the fabrication of integrated amplifiers, lossless components and lasers based on germanate glasses.
关键词： Optical materials,Laser processing,Optical spectroscopy,Amorphous materials
更新于2025-09-12 10:27:22