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Laser cooling arc plasma effect in laser-arc hybrid welding of 316L stainless steel
摘要： Current laser-plasma interaction theory supports that the plasma energy e.g. electron temperature would increase by the effect of inverse bremsstrahlung (IB) absorption, when a laser beam passed through the plasma. However, in this paper, we found an interesting laser cooling arc plasma effect (LCAPE) during kilo-Watt fiber laser-TIG hybrid welding. Based on theoretical modelling and experiments, we observed that a temperature decrease of more than 5000 K at the tail of the argon plasma occurred under different process parameters during hybrid welding of 316L stainless steel. We proposed the LCAPE is caused by the laser-induced metal vapor. The mechanism mainly includes the convection cooling and enhanced radiation of the arc plasma by the metal vapor. Our findings could broaden the theory of laser-plasma interaction and provide a theoretical reference to the modulation and control of plasma in industries.
关键词： Cooling effect,Stainless steel,Laser-arc hybrid welding,Arc plasma,Fiber laser
更新于2025-11-28 14:24:20
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Complementary use of pulsed and continuous wave emission modes to stabilize melt pool geometry in laser powder bed fusion
摘要： The most common defects in laser powder bed fusion (LPBF) namely porosity, geometrical errors, roughness and thermal deformations are principally linked with the energy input to the process. In common practice, a single set of process parameters is used to produce a whole component independently from the dimensions of the actual scan path within a given layer. However, melt pool stability is highly dependent on the scanned geometry. A possible strategy to maintain a constant melt pool is the mixed use of pulsed wave (PW) and continuous wave (CW) emission regimes. Accordingly, this work investigates the complementary use of continuous and modulated emission at fixed energy density on large and thin sections respectively. The proposed approach is tested on AISI 316L stainless steel and melt pool observations are conducted employing a coaxial monitoring system built for purpose. Temporally resolved measurements of intensity and geometrical properties of the melt pool were extracted as well as a three-dimensional spatial mapping of the molten pool area. The results demonstrate that moving from CW to a PW regime at the transition zones to thinner sections is effective in maintaining a constant melt pool size thus avoiding heat build-up and part extrusion from the powder bed.
关键词： Selective laser melting,Stainless steel,Molten pool monitoring,CW emission,PW emission
更新于2025-11-14 15:24:45
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AIP Conference Proceedings [Author(s) 4TH ELECTRONIC AND GREEN MATERIALS INTERNATIONAL CONFERENCE 2018 (EGM 2018) - Bandung, Indonesia (27–28 July 2018)] - The enhancement of the corrosion protection of 304 stainless steel using Al2O3 films by PLD method
摘要： The enhancement of the corrosion protection of 304 stainless steel using Al2O3 films by PLD method. In this manuscript, we are using PLD to reduce the corrosion rate of the stainless steel 304 in hydrochloric acid with the concentration of 1 M and the immersion time of 4 minutes at room temperature. This method opens prospects to use the enhanced stainless steel for many electronics and manufacturing applications.
关键词： PLD,corrosion,Al2O3 films,304 stainless steel
更新于2025-09-23 15:23:52
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Drag reduction effect of ultraviolet laser-fabricated superhydrophobic surface
摘要： Superhydrophobic (SH) surface has been found effective for drag reduction in wall-bounded turbulence for decades, especially the metallic durable SH surfaces are believed very promising for improving the velocity and voyage of marine vehicles. We present stainless steel SH surfaces with U-groove patterns that fabricated by ultraviolet laser texturing and coating modifier treatment. The drag-reducing effects of the SH surfaces are tested by a self-built gravity sliding speed improving evaluation device. The results show that the different drag-reduction performance of the SH surfaces can be achieved by adjusting the line spacing of the crossing U-groove patterns. With the line spacing equalling to 80 μm, the ultraviolet laser textured stainless steel SH surface acquires the static contact angle of 161.5° and the dynamic sliding angle of only 2°, which leads to the maximum speed improving rate of 29.7%.
关键词： drag reduction,Superhydrophobic surface,stainless steel,laser texturing
更新于2025-09-23 15:23:52
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Signal enhancement in laser diode thermal desorption-triple quadrupole mass spectrometry analysis using microwell surface coatings
摘要： Laser diode thermal desorption (LDTD) is an ionization source usually coupled to triple quadrupole mass spectrometry (QqQMS) and specifically designed for laboratories requiring high-throughput analysis. It has been observed that surface coatings on LDTD microwell plates can improve the sensitivity of the analysis of small polar molecules. The objective of the present study is to understand and quantify the effect of microwell surface coatings on signal intensity of small organic molecules of clinical, environmental and forensic interest. Experiments showed that the peak areas of diclofenac, chloramphenicol, salicylic acid and 11-nor-9-carboxy-Δ9-tetrahydrocannabinol obtained by LDTD-QqQMS increased by up to 3 orders of magnitude when using microwells coated with ethylenediaminetetraacetic acid (EDTA). Tests with different chelating agents and polytetrafluoroethylene as microwell surface coatings showed that nitrilotriacetic acid gave significantly higher peak areas for five out of the nine compounds that showed signal enhancement using chelating agents as coatings. Scanning electron microscopy studies of EDTA-coated and uncoated microwells showed that analytes deposited in the former formed more uniform and thinner films than in the latter. The enhancement effect of surface coatings in LDTD-QqQMS was explained mainly by the formation of homogenous and thinner layers of nanocrystals of analytes that are easier to desorb thermally than the layers formed when the analytes dry in direct contact with the bare stainless steel surface. Chemisorption of some analytes to the stainless steel surface of the microwell plate appeared to be a minor factor. Surface coatings widen the number of compounds analyzable by LDTD-QqQMS and can also improve sensitivity and limits of detection.
关键词： pharmaceuticals,high-throughput,hormones,pesticides,x-ray photoelectron spectroscopy,scanning electron microscopy,stainless steel,small organic molecules,chelating agents
更新于2025-09-23 15:23:52
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Formation of Stainless Steel Nanoballs via Submerged Glow-discharge Plasma and their Microstructural Analysis with Evaluation of Photocatalytic Activity
摘要： Stainless steel has shown potential as a catalytic material in bulk form. However, it only becomes active in an aqueous acidic environment and elevated temperatures. This study aims to produce stainless steel nanoparticles that have high photocatalytic activity in a neutral medium and at room temperature and to elucidate the photocatalytic activity mechanism of the nanoparticles. Spherical, photocatalytic nanoparticles called 'nanoballs' were synthesized by the submerged glow-discharge method. Stainless steel SUS316L grade wire was used as the cathode, platinum mesh was used as the anode while the electrolyte was potassium carbonate. The nanoballs were obtained after centrifuging and washing with water. The physical characteristics of the photocatalytic nanoballs were analysed by scanning electron microscopy, high-resolution transmission electron microscopy, energy-dispersive X-ray spectroscopy and X-ray diffraction. The nanoballs were mixed with methylene blue and irradiated with ultraviolet light for the evaluation of photocatalytic reaction. The photodecomposition samples were determined using UV-vis spectrometry. The by-products of the photodecomposition were evaluated using mass spectrometry. The results show that stainless steel nanoballs have photocatalytic activity when irradiated with ultraviolet light at room temperature. Submerged glow-discharge plasma method can synthesize nanoparticles rapidly using only metal wires as the electrode.
关键词： photocatalysis,nanoballs,stainless steel,plasma discharge,nanoparticles
更新于2025-09-23 15:22:29
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Effects of LNO buffer layers on electrical properties of BFO-PT thin films on stainless steel substrates
摘要： Ferroelectric 0.7BiFeO3-0.3PbTiO3 (BFO-PT) thin films were deposited on LaNiO3 (LNO) coated stainless steel (SS) substrates by the sol-gel method. XRD results indicate that both LNO and BFO-PT thin films have the perovskite structure and the film crystallinity is improved with increasing the LNO thickness. The dielectric loss of BFO-PT thin films is reduced significantly with addition of LNO buffer layers, achieving about 4 % at the frequency of 1 kHz, much lower than that of > 20 % for BFO-PT thin films directly deposited on SS substrates. BFO-PT thin films reveal the strong ferroelectricity with remnant polarization (Pr) of about 35 m C/cm2 for LNO of 390 nm. Moreover, addition of LNO buffer layers mitigates the polarization deterioration after the 1.33×108 switching cycles resulting in the improved anti-fatigue properties of BFO-PT thin films. Our results indicate that BFO-PT/LNO multilayer thin films on SS substrates maintain excellent dielectric and ferroelectric properties.
关键词： 0.7BiFeO3-0.3PbTiO3 thin films,Stainless steel substrates,LaNiO3
更新于2025-09-23 15:22:29
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Dynamic Laser Absorptance Measured in a Geometrically Characterized Stainless-Steel Powder Layer
摘要： The relationship between real powder distributions and optical coupling is a critical building block for developing a deeper physical understanding of laser-additive manufacturing and for creating more reliable and accurate models for predictable manufacturing. Laser-light absorption by a metal powder is distinctly different from that of a solid material, as it is impacted by additional parameters, such as particle size, shape distribution, and packing. Here, we use x-ray computed tomography to experimentally determine these parameters in a thinly spread austenitic stainless-steel powder on a metal substrate, and we combine these results with optical absorptance measurements during a 1 ms stationary laser-light exposure to simulate the additive-manufacturing process. Within the thinly spread powder layer, the particle volume fraction changes continuously from near zero at the powder surface to a peak value of 0.72 at a depth of 235 μm, with the most rapid increase taking place in the first 100 μm. The relationship between this particle volume fraction gradient and optical absorptance is investigated using an analytical model, which shows that depth-averaged absorptance measurements can measure the predicted average value, but will fail to capture local effects that result from a changing powder density. The time-averaged absorptance remains at levels between 0.67 and 0.80 across a two orders of magnitude range in laser power, which is significantly higher than that observed in solid stainless-steel experiments. The dynamic behavior of the absorptance, however, reveals physical phenomena, including oxidation, melting, and vapor cavity (keyhole) formation, as well as quantifying the effect of these on the absorbed energy.
关键词： keyhole formation,laser-additive manufacturing,stainless-steel powder,x-ray computed tomography,optical coupling,optical absorptance,particle volume fraction
更新于2025-09-23 15:21:01
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Optimisation of edge quality on stainless steel 316L using low power fibre laser beam machining
摘要： In the manufacturing industry critical importance lies upon the dimensional accuracy of a machining part especially for precision assembly operation in sheet metal cutting. But the converging diverging shape of the laser beam profile causes the existence of kerf taper in laser cut specimen. Use of low power fibre laser beam machining in the order of 50 watt makes it extremely difficult to perform good quality cut on stainless steel sheet metal. Cutting wedge angle, a relatively uncommon process variable performs a critical role for the determination of unevenness in kerf characteristic. Cutting result of kerf taper with a 50-watt fibre laser is presented in this investigation. The purpose of the investigation is to reveal the ability of the low power fibre laser to cut stainless steel AISI 316 L with 1 mm thickness. The effect of the cutting wedge angle and other process variables like power, duty cycle, pulse frequency and scanning speed has been analysed through an application of Response Surface Methodology (RSM) with CCD technique. Validation of experiments on the proposed model reveals that adjustment of proper process parameters can optimise the required edge quality.
关键词： Laser cutting,response surface methodology,kerf taper,cutting wedge angle,AISI 316 L stainless steel
更新于2025-09-23 15:21:01
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Pore Formation during Laser Welding in Different Spatial Positions
摘要： The process of formation of pores, cavities and similar defects in welded joints of stainless steels and aluminum alloys, affecting their quality, directly depends on spatial weld position in laser welding. Reducing the angle of inclination from 90° to 0° during downhill and uphill welding of AISI 321 stainless steel in the pulse mode of laser generation leads to an increase in both the number of pores and their size. At the same time, defects in the form of pores are not observed in the continuous mode of laser generation. In laser welding of butt joints of AISI 321 steel, the flat and vertical weld positions are the most promising, as they provide the highest level of quality. In order to provide a stable formation of a high-quality butt joint of aluminum AMg6M alloy and to prevent the failure of laser equipment, the welding process should be carried out in a vertical uphill weld position.
关键词： different spatial position,aluminium alloy,stainless steel,quality,defects,porosity,laser welding
更新于2025-09-23 15:21:01