Continuous CO2 Laser Beam Research Articles

Влияние построчного лазерного сканирования на свойства лазерно-индуцированного графена

Technology of polyimide (PI) film carbonization by direct laser treatment attracts much attention due to the versatility and ease of obtaining the carbon material, laser-induced graphene (LIG), used in the creation of various sensors and functional devices. In this work LIG film structures are obtained by line-by-line scanning of a continuous CO2 laser beam over the surface of the PI film. The synthesized carbon film material is studied by optical and scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. It is shown that the Raman spectra of a single LIG line and a set of overlapping LIG lines significantly differ from each other. It is found that multiple laser scanning of the PI film leads to a marked decrease in the number of defects in the LIG structure as well as to a significant decrease in the specific surface resistance of the synthesized film material. The results obtained can be used in the synthesis of LIG film structures with improved characteristics.

Corrosion Resistance of Coatings Produced by Spraying Powders Under a Laser Beam in a Saline Environment NaCl 3% by the Electrochemical Method

Abstract The manuscript focuses on the study of corrosion resistance in NaCl medium of a 304L type stainless steel after application of protective nickel-based and cobalt-based coatings produced by powder spraying under a continuous CO2 laser (10.6 µm wavelength) beam. Using polarization and electrochemical impedance spectroscopy methods, the results found confirm that metallic coatings produced under high energy beams offer excellent protection up to an efficiency of E = 98.12% in aggressive environments with salinity to 3%.

Impact of γ-Irradiation on the Kinetics of Laser Ablation of Polyamide Under Continuous CO2 Laser Beam

The effect of preliminary γ-irradiation on accelerating the speed of laser ablation of a polyamide is measured for the first time. A linear increase of intensity with a rate of 0.15 mg/s is observed during laser ablation of the polyamide pre-irradiated with γ-rays at a dose of 3,500 kGy. A γ-radiolysis dose of 10 – 20 kGy causes extreme changes in the molecular-topological parameters and the maximum level of growth of the rate of laser ablation. Thus pre-irradiation with γ-rays may be used to optimize the laser ablation of the polymer.

Study on Thermal Stress Cleavage of Chemically Strengthened Glass by CO2 Laser Beam

This study deals with the thermal stress cleavage of chemically strengthened glass by CO2 laser beam irradiation. In order to prevent breakage from external stress, the surface of chemically strengthened glass is load with compressive stress by ion-exchanging methods. Generally, thermal stress cleavage occurs because of tensile stress on the brittle material. This stress is induced by laser beam irradiation. Therefore, the compressive stress on the surface of chemically strengthened glass renders the thermal stress cleavage difficult to create. It is also difficult to introduce an initial crack on the surface. In this study, cleavage characteristics of chemically strengthened glass with a thickness of 0.7mm are investigated experimentally. The depth of compressive stress from the surface is 33μm. The laser used is a continuous CO2 laser beam with a wavelength of 10.6μm. This laser is also applied to the introduction of the initial crack at the edge of the chemically strengthened glass. Additionally, the influence of laser power and energy density on the introduction of the initial crack and the thermal stress cleavage are evaluated. From these results, in order to propagate the initial crack, the depth of the initial crack needs to exceed the depth of the compressive stress layer from the surface. The depth of the initial crack tends to increase with increasing energy density. When an initial crack is introduced along the cleaving line, the quality of the cleaved surface is poor. The quality of cleavage was improved by the introduction of an initial crack at the edge of the glass.

Prediction of drilling micro-hole in CO2 laser irradiated sticking plaster

This paper reports a simulation model of drilling micro-hole in sticking plaster heated with a 1064 nm continuous CO2 laser beam. Laser spot sizes ranged from 0.1 to 0.2mm diameter with axial irradiance power levels of 25–100W. To apply software Ansys, the measured steady-state surface temperature is calculated to rise with both increasing beam power and incident laser irradiance. For temperatures above 450 °C, sticking plaster vaporized into ventilation hole, and the size of ventilation hole 0.15mm diameter spent 1.7ms heated with laser power lever of 100W with the size of spot 0.15mm diameter, in good accordance with reported in earlier experiments studies. Similarly, the size of ventilation holes changed with beam power and laser spot diameter. These results show that software Ansys can be used to predict drilling micro-hole in CO2 laser irradiated sticking plaster and the result of simulation can guide to laser drilling experiments.

Fundamental Study on Laser Leveling of Sheet Metal

Laser leveling is an application of laser forming. Laser leveling of a sheet metal is a plastic process caused by thermal stresses which are produced in the sheet by laser irradiation. In this paper, a sphereical distortion on a sheet metal is leveled by laser irradiation. As a model of a circular distortion, the dsitortion is intentionally introduced on the sheet metal by pressing a steel ball of 25 mm radius against it. As work materials, steel sheet and stainless steel sheet whose thickness is 0.6mm are used. Laser beam is radially irradiated at the center of circular distortion for leveling the distorted sheet metal. Continuous CO2 laser beam is used and its power is changed at the range of 80W ∼ 200W under a constant scanning speed of 2mm/s. After laser irradiation, a distortion of about 400µm hight becomes almost flat without melting a sheet metal.

Laser induced modification on 40BaO–45B2O3–15TiO2 glass composition

This paper describes a study concerning the permanent modification of 40BaO–45B2O3–15TiO2 (mol%) glass composition when irradiated by a continuous CO2 laser beam. Three parameters of the permanent modification and crystallization processes induced by irradiation were studied: laser power, irradiation time and the presence of micrograins of β-BaB2O4 (β-BBO) crystalline phase on the glass sample surface prior to irradiation. The geometry of permanent deformation induced by irradiation depended mainly on the laser power and sample surface condition. Crystallization of the irradiated region was observed when laser power at around 0.72W and an irradiation time of around 300s were used. The structural characterization performed by micro-Raman and X-ray diffraction techniques showed the formation of only the BaTi(BO3)2 crystalline phase on the as-polished sample. On the other hand, when β-BBO microcrystals were homogeneously dispersed onto the glass surface, the formation of the β-BBO phase was induced. In this condition, the β-BBO becomes the main crystalline phase and presents a certain degree of texture.

Ablation of polytetrafluoroethylene using a continuous CO2 laser beam

The ablation of polytetrafluoroethylene (PTFE) is studied using a continuous CO2 laser beam of 30–50 W at a mean intensity of 0.05–50 MW m−2. The ablation products and changes in the target layer are examined using infrared spectroscopy, x-ray photoelectron spectroscopy, x-ray diffraction and electron microscopy. The main experiments were conducted with an unfocused beam of intensity 0.9–1.2 MW m−2. The radiation–polymer interaction characteristics were found to change appreciably as the ablation conditions are approached. Within the polymer layer, light scattering diminishes and true resonant light absorption increases. Two distinct polymer components, which differ primarily in their resistance to CO2 laser radiation, were found to exist under ablation conditions. The less stable component depolymerizes intensively, while the more resistant component is blown up into fibres by intense gas flow. The reasons behind this behaviour are discussed. Preliminary gamma irradiation of PTFE is found to have a significant influence on the laser ablation process.

Strength of Cylindrical Specimens Subjected to Laser Hardening along the Generator and a Spiral Path

We have shown that the path of a continuous CO2-laser beam over the cylindrical surface of specimens in the course of their hardening substantially affects the strength of steels in cyclic axial tension and bending with torsion. Hardening on a spiral path ensures higher mechanical parameters as compared with that along the generator of the cylindrical surface.

Role of Overlapping Passes on Fatigue Performance of Microalloyed 17MnCuNi7 Steel Treated by Continuous CO2 Laser Beam

The widely used surface treatment by continuous CO2 laser beam requires superposition of several laser passes, which can lead to a softened zone and to the creation of tensile residual stresses in overlapping passes. In this study, the effect of overlapping passes, microhardness, and metallurgical transformations on the fatigue performance of 17MnCuNi7 steel has been investigated by three series of bending fatigue tests corresponding to three types of continuous CO2 laser beam treatments. It has been concluded that suitable selection of material and control of the laser treatment parameters provides for the elimination of tensile residual stresses in softened zones, and can lead to homogeneous hardening of the surface. The fatigue limit of 17MnCuNi7 steel depends mainly on the residual stress in the layers affected by laser treatment, despite any hardness loss caused by overlapping passes. The improvement made by this treatment varies from 10 to 20% compared with the fatigue limit in the tempered state.

Long ropes of boron nitride nanotubes grown by a continuous laser heating

A continuous CO2 laser beam was focused on a surface of hexagonal boron nitride under low nitrogen pressure, inducing a stiff radial temperature gradient, rising locally over the dissociation temperature. Boron nitride nanotubes and faceted boron nitride onions were found on the heated surface, segregated in specific zones. Nanotubes were grown in macroscopic quantity, stoichiometric, well crystallized, mostly with few layers, and self-assembled in ropes as long as 40 μm. The cavity of boron nitride onions was often occupied by a boron nanocrystal. The recombination of boron and nitrogen both in plasma and on surface is suggested for the nucleation process.

Surface alloying of iron by laser melting: microstructure and mechanical properties

Superficial laser induced melting produces non-equilibrium phases without changing the microstructure of the bulk and therefore alters specimen properties. Nitrided steels are of interest in a wide range oftechnological applications because of increased hardness and corrosion resistance as well as interesting magnetic and electrical properties. The aim of the present study was to determine the influence of nitride coatings (y’-Fe4N, ε-Fe3–2N, α″′-Fe8N, BN, AlN, and Cr2N) on the superficial alloying, microstructure, and microhardness of Armco iron melted with a continuous CO2 laser beam at a power level of 400 W Depending onmelting conditions as well as thickness and chemical composition of the coating, ferrite, martensite, austenite, γ’, or ε phases are detected at the surface of laser alloyed iron using Mossbauer spectroscopy, X-ray diffraction, and optical microscopy. The microhardness can be considerably increased depending on the microstructure and residual stresses in the surface layers.

Structure and morphology of titanium nitride films deposited by laser-induced chemical vapour deposition

Results on the deposition of titanium nitride on AISI M2 tool steel-type substrates by pyrolytic laser chemical vapour deposition are reported. Spots of TiN were deposited from a gas mixture of TiCl4, nitrogen and hydrogen using a continuous wave quasi-TEMoo CO2 laser beam. The morphology and the structure of the deposited material were investigated by optical microscopy, scanning electron microscopy and X-ray diffraction. The chemical composition was studied with a scanning electron microscope with an energy dispersive spectrometer, and with an electron probe microanalyser. The topography of the coating was analysed with a stylus profilometer and different thickness profiles were measured depending on the laser-power densities and irradiation times. The morphology of the films showed a strong dependence on the laser-power density, interaction time and partial pressure of TiCl4.

LASER SURFACE TREATMENTS FOR PROMOTING CORROSION RESISTANCE OF A CARBON STEEL

ABSTRACT The effect of laser treatment and laser alloying on corrosion resistance of 1045 steel has been studied. Various ways of surface alloying have been investigated by using continuous CO2 laser beam: i) irradiation of chromium painted surfaces; ii) irradiation of Ni and Cr-electroplated surfaces; iii) direct injection of Ni and Cr powders into the melt pool. A high and uniform level of alloying in the surface layer can be achieved in the cases of electroplated surfaces and direct powder injection. It requires, however, an appropriate choice of irradiation conditions (such as beam power, beam traverse speed, beam defocusing and degree of overlapping) that provide remelted layer of a limited and fairly uniform thickness. It has been found that in order to achieve corrosion behavior of laser treated surfaces similar to that of austenite type 304 stainless steel chromium and nickel contents in the alloyed layer are to be higher than those of 304 steel.

Mössbauer spectroscopy of laser surfaces treated metallic materials

Laser treated surfaces of the Fe83Si17 alloy and of the coatings prepared on low-carbon steel by laser surface alloying with Ni and Al were investigated by means of Mossbauer spectroscopy. The short range order in the surface layer after irradiation by neodymium laser pulses was found to be similar to that before irradiation. The high quenching rate of a single melt pool after single pulse action seems to be masked by annealing due to the heat produced by successive pulses covering the whole surface. A detailed phase analysis of the coatings prepared by laser surface alloying was done. Seven different phases were found in dependence on chemical composition of alloy coatings and on traverse speed, i.e. the speed of relative motion of sample and the continuous CO2-laser beam.

Synthesis of Nb3Ga and Nb3Al superconducting composites by laser beam irradiation

Nb3Ga and Nb3Al superconductors were successfully fabricated by continuous CO2 laser beam irradiation of a moving material. Transition temperatures after the irradiation are 17.0 and 16.5 K, respectively. These temperatures are increased by ∼2 K by the subsequent annealings. Critical current density Jc (for the reacted area) of 3×104 A/cm2 at 15 T and 4.2 K is obtained for Nb3Al tape with small magnetic field dependence up to 23 T. The results indicate that the continuous laser beam irradiation is a very attractive method for fabricating advanced superconductors, such as Nb3Ga, Nb3Al, Nb3(Al,Ge), etc.

Phase changes in a laser-alloyed Fe-5Cr steel

Laser surface alloying is a relatively new method to modify metal surfaces. A suitably applied metal coating and an underlying metal substrate are rapidly melted by a high power, continuous laser beam. The resultant melting, mixing and rapid solidification can be controlled to form an alloyed fusion zone at the surface with the desired mechanical properties.In this work, Ni-Cr and Ni-Cr-WC metal powders were thermally deposited on a Fe-5Cr steel. Coating parameters were adjusted to achieve desired coating thicknesses. Laser processing was carried out with a continuous CO2 laser beam capable of power densities up to 108 watts/sq.cm. to alloy the metal powder with the base material. Power density, scan rate, spot size and other parameters were all controlled to produce penetration depths of up to 850μm (Table 1). Interpass steps were adjusted to produce both overlapping and discrete fusion zones.

The use of laser surface melting to homogenize Fe-Al bronzes

Laser surface melting has been used to homogenize the near-surface region of several Fe-Al bronzes. A continuous CO2 laser beam was focussed onto the sample surface while the samples moved at high velocities in order to produce melt stripes. The quenched regions were approximately 10μm deep. In the case of the aluminium bronzes C-61 400 and C-62 400 iron-rich precipitates have been eliminated from the surface region. For C62 400 the pre-irradiation matrix isα +γ 2, following laser processing, a single phase, presumably metastableβ, is formed in the quenched region. The aluminium bronze C-62 500 is not homogenized to the same degree as the C-61 400 or C-62 400. Sample analysis was carried out utilizing optical microscopy, scanning electron microscopy, energy dispersive X-ray analysis and scanning Auger microscopy.

Disintegration of Urinary Calculi by Laser Beam: Drilling Experiment in Extracted Urinary Stones

Disintegration of urinary calculi was attempted by the use of laser beam. As a first step, drilling of extracted urinary stones was attempted using a continuous wave CO2 laser and a pulse ruby laser. Stones were drilled easily by either laser beam. The power around 10 W of continuous CO2 laser beam was sufficient to drill through the stone.

Subsonic plasma motion in continuous laser light

An analysis of the motion of a subsonic plasma in a continuous CO2 laser beam indicates that the radial thermal expansion of the plasma is the rate-controlling effect. Plasma extinction was found to occur at an ionization degree of approximately 10%, which corresponds to a flux of less than 104 W cm−2; this is two orders of magnitude below values previously reported.