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Tribological performance of metal-reinforced ceramic composites selectively structured with femtosecond laser-induced periodic surface structures
摘要： The impact of femtosecond (fs) laser-induced periodic surface structures (LIPSS) on tribological properties was investigated for metal-reinforced ceramic composites (Al2O3-ZrO2-Nb). For this purpose, the metallic niobium (Nb) phase was selectively structured with LIPSS in an air environment with different values of the fs-laser peak fluence by near-infrared fs-laser radiation (λ = 1,025 nm, τ = 300 fs, frep = 1 kHz), taking advantage of the different light absorption behavior of ceramic and metal. The tribological performance was evaluated by reciprocating sliding tests in a ball-on-disc configuration using Ringer’s solution as lubricant. The surfaces were characterized before and after laser irradiation by optical microscopy, scanning electron microscopy, atomic force microscopy, X-ray photoelectron spectroscopy, energy dispersive X-ray spectroscopy and by measuring the contact angle with Ringer’s solution. The LIPSS formation resulted in an increased wetting of the surface with the lubricant. Moreover, the selectively structured composite surfaces revealed a coefficient of friction significantly reduced by a factor of ~ 3 when compared to the non-irradiated surface. Furthermore, the formation of a laser-induced oxidation layer was detected with NbO as the most prominent oxidation state. Selectively structured composites with outstanding mechanical properties and enhanced tribological performance are of particular interest for biomedical applications.
关键词： femtosecond laser-induced periodic surface structures (LIPSS),tribology,wettability,ceramic matrix composites,coefficient of friction,selective surface structuring
更新于2025-09-12 10:27:22
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Laser-assisted micro-milling of austenitic stainless steel X5CrNi18-10
摘要： This paper presents a novel Laser-Assisted Micro-Milling (LAMM) process of austenitic stainless steel X5CrNi18-10. The LAMM process is compared with the conventional micro-milling process. Ultra-short pulsed laser radiation is utilized for the structuring of the workpiece surface prior to the micro-milling process. Different laser structures are produced on the workpiece surface at a constant laser scanning speed with various laser powers and laser line spans. The high performance of the developed process is shown by experimental investigations. The effect of laser structuring on the micro-milling forces and temperature indicated the superior performance of the new LAMM process. Cutting forces and temperature could be reduced by up to 70% and 50%, respectively. The results of conventional micro-milling showed that increasing the cutting speed, at a constant undeformed chip thickness, reduced the micro-milling forces. Increasing the cutting speed from 50 to 250 m/min halved both the trust and normal forces, while it slightly improved the surface roughness. On the other hand, increasing the feed per tooth degraded the surface roughness and increased the cutting forces. Furthermore, in conventional milling the workpiece was subjected to high plastic deformation during the cutting process, while side flow, smeared material, metal debris, and cavities were observed on the workpiece surface.
关键词： Laser-assisted micro-milling,Austenitic stainless steel,Ultra-short pulsed laser,Laser structuring,Micro-milling
更新于2025-09-12 10:27:22
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Heat accumulation effects in laser processing of diamond-like nanocomposite films with bursts of femtosecond pulses
摘要： In this paper, we have investigated the burst mode (BM) ablation and surface structuring of diamondlike nanocomposite (DLN) a-C:H:Si:O films with femtosecond laser pulses (wavelength λ = 515 nm, pulse duration τ = 320 fs, and pulse repetition rate f = 100 kHz) under different scanning conditions (single spots and linear structures). The pulse separation in the bursts is 25 ns (intraburst frequency f = 40 MHz), and the pulse number is varied from 1 to 8. The ablation depth and specific ablation rates (μm3/μJ) are found to be higher for the burst mode compared to single-pulse irradiation, increasing with the pulse number in the burst. The obtained experimental data of the higher ablation efficiency are shown to correlate with computer simulations of the BM ablation. In correlation with the ablation findings, Raman spectra of single spots and microgrooves have evidenced a growing graphitization of the amorphous film structure with the pulse number in the bursts (at an equal energy deposited into the films). Contact-mode atomic force microscopy (AFM) is applied to reveal an influence of the BM processing on the surface properties (nanoscale relief, friction) of laser-structured films. Based on the ablation and Raman data analysis, AFM examination of ablated/redeposited layers, and computer simulations of the burst mode ablation, the heat accumulation is identified as the main factor responsible for the enhanced ablation efficiency during the BM processing of DLN films. In addition, results of the high precision surface microstructuring of DLN films in the burst mode are presented.
关键词： heat accumulation,diamondlike nanocomposite films,surface structuring,femtosecond laser pulses,burst mode ablation
更新于2025-09-12 10:27:22
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Narrower Far Field and Higher Efficiency in 1 kW Diode-Laser Bars using Improved Lateral Structuring
摘要： High power, efficient diode-laser bars with narrow far field angles are sought for many applications, for example in the 9xx nm-range for the pumping of Yb:YAG disc and slab lasers. In previous work, broad-area (BA) diode-laser bars with 4 mm resonator length operated with high conversion efficiency η = 62% at operating power Pop = 1 kW in quasi-continuous wave testing (200 μs, 10 Hz), by using low optical loss and low-resistivity vertical structures and high fill-factors (~70%). Lateral far field (95% power) was θ95% > 10°. However, higher η and narrower θ95% are needed for industrial application, and we seek improvements by altering the lateral bar structure for a fixed vertical design (from [1], wavelength λ = 930 nm, loss αi ≈ 0.4 cm-1). First, narrower θ95% at Pop = 1 kW was sought. In previous studies on 90 μm-wide single emitters, deep implantation through the active region was shown to reduce gain at the emitter edges, suppressing higher-order lateral modes, for smaller θ95%, at the price of reduced η and Pop. A similar implantation approach is assessed here in high fill-factor bars, and the drop in η is mitigated by reducing the implantation depth. Second, higher η at Pop = 1 kW was sought, by increasing the fill-factor, for lower electrical resistance.
关键词： lateral structuring,efficiency,narrow far field,high power,diode-laser bars
更新于2025-09-12 10:27:22
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Laser radiation impact on a solid surface and formation of micro- and nanostructures
摘要： The work is devoted to the problem of micro- and nanostructuring of the surface of solids as a result of exposure to laser radiation. The method of forming periodic surface structures by means of femtosecond laser processing is presented using the example of solving the problem of titanium structuring.
关键词： femtosecond laser processing,micro- and nanostructures,laser radiation,titanium structuring
更新于2025-09-12 10:27:22
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Femtosecond laser-induced non-centrosymmetric surface microstructures on bulk metallic glass for unidirectional droplet micro-displacement
摘要： Unidirectional droplet motion without energy input has attracted considerable attention in various potential applications. We report on the fabrication of unconventional laser-induced periodic surface structures (LIPSS) for unidirectional droplet micro-displacement by femtosecond laser at large incident angle. In order to overcome the mechanical durability of the existing soft materials such as PDMS for controlling the droplet, Zr-based bulk metallic glass (Zr-BMG) is used to fabricate the typical non-centrosymmetric unconventional LIPSS, which include micro-sized elliptical arc-shaped structures and nano-ripples with the central spatial periodicity of 400 nm. The spots and the grating of unconventional LIPSS on Zr-BMG are fabricated to construct the functional surface structures by femtosecond laser irradiation. The unidirectional micro-displacement of water droplet on Zr-BMG was achieved using functional surface structures. For better understanding the fabrication of unconventional LIPSS, the underlying formation mechanism was revealed by numerical simulations. This work gives a fast, precise and low-cost method to fabricate the non-centrosymmetric surface micro/nano-structures on metal materials for unidirectional droplet motion in microfluidics.
关键词： laser surface structuring,unidirectional droplet motion,LIPSS,bulk metallic glass,Ultrafast laser
更新于2025-09-11 14:15:04
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Surface micro-structuring of type 304 stainless steel by femtosecond pulsed laser: effect on surface wettability and corrosion resistance
摘要： This paper presents results on femtosecond (fs) pulsed laser-based surface micro-structuring of type 304 stainless steel (304 SS). Post laser treatment surface wettability and corrosion resistance investigation are reported. SS sample surfaces have been micro-structured using a typical laser fluence of ~ 0.9 J/cm2 for varying sample scanning speed in the range 25–1000 μm/s. Dense array of micro-protrusions have been generated without formation of a crater for an optimized target scan speed exceeding 200 μm/s. Static water contact angle (WCA) measurement indicated super-hydrophilic behavior immediately after laser treatment. However, hydrophilicity (wettability) was found to decrease with storage time with sample becoming highly hydrophobic (WCA: 144° ± 5°) within 50 days after laser treatment. Corrosion resistance of the laser-treated samples was measured by potentio-dynamic polarization technique. Fs laser micro-structured SS has shown poorer corrosion resistance in comparison to pristine surface. Observed poorer corrosion resistance of laser-treated surface has been explained on the basis of surface chemical composition and surface roughness. The results demonstrated that corrosion resistance increased with increasing hydrophobicity of the SS surface.
关键词： corrosion resistance,femtosecond pulsed laser,stainless steel,surface micro-structuring,wettability
更新于2025-09-10 09:29:36
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Anti-corrosion prevention of carbon steel by means of laser treatment
摘要： The article is devoted to the research of the opportunity for the increasing corrosion resistance of steel. The results of the experiments of laser processing of model samples made of carbon steel with CW ytterbium fiber laser at a wavelength of 1.06 micron. It is shown that laser processing can form resistant protective film with a thickness of 2–3 microns on the steel surface, which improve anti-corrosion properties of metal. One of the possible reasons for the increase in corrosion resistance of steel is the microstructuring of its surface to form a thin film of iron carbide (Fe3C), which is formed as a result of heating in the temperature range from 600 to 1000 °C. Besides, the exposure to laser radiation leads to reduction of surface roughness (from Ra = 0.53 μm to Ra = 0.48 μm). Optimal (from the point of view of the degree of resistance to corrosion) steel processing mode corresponds to the density level of laser radiation power density of 1.5 · 105 W cm?2, the conducted research allows to conclude that the use of CW fiber lasers is a promising method of improving the corrosion resistance of carbon steel.
关键词： fiber laser,steel treatment,anti-corrosion,laser micro structuring,metal treatment
更新于2025-09-04 15:30:14