Laser Treatment Modes Research Articles

ВЛИЯНИЕ ЛАЗЕРНОЙ МОДИФИКАЦИИ ПОВЕРХНОСТИ НА ФИЗИКО-МЕХАНИЧЕСКИЕ И ТРИБОЛОГИЧЕСКИЕ СВОЙСТВА ШТАМПОВОЙ СТАЛИ

The effect of laser modification of the surface on the value of the coefficient of elasticity, hardness, coefficient of friction and the amount of wear of the counterbody when testing pro­ducts made of tool die steel H12MF was investigated. The SVAROG-1-5DR laser complex (Russia) was used for laser processing. When setting different modes of laser processing, the power of laser radiation, the speed of movement of the laser beam relative to the treated surface and the focal length were varied. The measurement of Vickers hardness and wear resistance indicators was carried out using the MicroCombiTester and Tribometer units of the firm CSM Instruments (Switzerland). Rockwell hardness was measured using a TN 301 hardness tester from Time Group (China). The alloy structure was studied by metallography and X-ray diffractometry. It was found that the indicators of hardness and wear resistance of the surface layers of steel H12MF strongly depend on the laser treatment modes. These dependencies are extreme in nature, have maximums and minimums. The paper presents quantitative values of hardness and wear resistance indicators before and after laser treatment of the surface of this steel according to different modes. The reasons for the change in the hardness and wear resistance of the surface layers of steel H12MF after laser treatment according to various modes have been established. The results of the work were used to optimize the modes of laser surface treatment of steel H12MF in order to obtain maximum values of hardness and wear resistance. It has been shown that laser treatment of steel H12MF without melting is promising in terms of increasing hardness and reducing friction. The mode of laser modification of the SVAROG-1-5DR complex was obtained, which allows increasing the hardness by 55.5% while reducing the coefficient of friction by 12.9% and reducing wear by 27.3%.

The Use of Laser Surface Modification Technologies for Obtaining Parts of Roller-Screw Mechanism

A number of parts of roller-screw mechanisms (RSM), which work in aggressive environments, are made of corrosion-resistant stainless steel 40Cr13 (AISI420 analogue). These elements include a screw and rollers. For these parts, it is necessary to have hard surface layers and a soft core. A promising method for obtaining the necessary requirements is surface laser modification. The article investigated the effect of laser surface treatment on the value of the coefficient of elasticity, hardness, coefficient of friction and the amount of wear of products made of stainless alloy steel 40Cr13. For laser processing, the SVAROG-1-5DR laser complex (Russia) was used. Various modes of surface laser modification were set. For this purpose, the power of the laser power, the speed of movement of the laser beam relative to the treated surface, and the focal length were varied. The Vickers hardness and tribological characteristics were measured using a microcombitester and tribometer manufactured by SSM Instruments SA (Switzerland). The Rockwell hardness was measured using a TN 301 hardness tester manufactured by Time Group (China). The structure of the alloy was studied by metallography and X-ray diffractometry. It was found that the indicators of hardness and wear resistance of the surface layers of sctructural 40Cr13 steel strongly depend on the laser treatment modes. These dependencies are extreme, with highs and lows. The paper presents the quantitative values of the hardness and wear resistance indicators before and after laser treatment of the surface of this steel in various modes. The reasons for the change in the hardness and wear of the surface layers of 40Cr13 steel after laser treatment under different modes are established. The results of the work were used to optimize the modes of laser treatment of the surface of 40Cr13 steel in order to obtain the maximum values of hardness and wear resistance.

Determination of the optimal mode of laser surface marking of aluminium composite panels with CO2 laser

This research examines an approach for finding the optimal modes of laser treatment with CO2 laser on advertisement boards made of aluminium composite panels. To achieve the optimal area of the processing mode, an experimental methodology has been developed and an experiment has been planned for finding the limits at the given parameters of the speed and power to obtain an optimisation model. The optimal results are obtained at speeds from 100 to 200 mm/s along the x and y operative axes, as well as the power limits from 5 to 7.5 W to obtain a clear and well-defined image. The defined theoretical mode, obtained because of multicriteria optimisation, is implemented in practice. It is defined as having the relatively best quality image obtained in the shortest time.

Groove Formation on Metal Substrates by Nanosecond Laser Removal of Melted Material

An effective strategy to produce grooves on carbon steel substrates by nanosecond laser radiation is proposed. The aim is to increase the productivity of grooves creation. In this study, two different modes of laser treatment are compared. The first mode focuses on the evaporation of material, while the second focuses on the formation of melted material and its removal by the action of pressure vapors produced by evaporated material. Within some ranges of processing parameters, the shape of the groove can be linearly controlled. The dependence of the groove depth also has a logarithmic nature when the number of passes is increased. Using the liquid phase mode in some ranges of parameters can reduce the amount of evaporated material in comparison with standard techniques in which the material is removed in the form of gas, and fine dust is emitted.

Hardness of the Powder Coating PG-CP4 Applied to Steel 40H13 and Subjected Laser Treatment

The article examines the hardness of the coating made of PG-CP4 powder. Plasma powder deposition was performed to samples made of 40H13 steel and then the samples treated with a laser beam. A multi-factor model was established that relates the hardness of the protective coating to the radiation power W, the longitudinal feed Spr of the laser beam, and the distance L from the protective casing of the laser head to the treated surface. Depending on the laser treatment modes, coating was in a state of complete, partial reflow or its absence. Full reflow is characterized by the adhesion of the filler material to the substrate, by maximum hardness of HRC 51.2–56.6 and no defects. In the absence of reflow, gas sinks, transverse microcracks, detachments, and other defects were found in the coating material, and the hardness decreased to HB 125–212. An increase in W and a decrease in Spr lead to increases the hardness of the treated coating, which is explained by an increase in the specific heat flux supplied to the coating per unit time, and a high rate of heat removal deep into the surface layer of 40H13 steel. The thickness of the surface layer with increased hardness ranged from 0.1 to 1.5 mm. Based on the multi-factor model, laser processing modes are controlled to ensure the required values of the protective coating hardness. The research results are recommended for use in enterprises that implement laser technologies and develop modern laser systems.

Laser Processing of Polymer Films Fabricated from PHAs Differing in Their Monomer Composition.

The study reports results of using a CO2-laser in continuous wave (3 W; 2 m/s) and quasi-pulsed (13.5 W; 1 m/s) modes to treat films prepared by solvent casting technique from four types of polyhydroxyalkanoates (PHAs), namely poly-3-hydroxybutyrate and three copolymers of 3-hydroxybutyrate: with 4-hydroxybutyrate, 3-hydroxyvalerate, and 3-hydroxyhexanoate (each second monomer constituting about 30 mol.%). The PHAs differed in their thermal and molecular weight properties and degree of crystallinity. Pristine films differed in porosity, hydrophilicity, and roughness parameters. The two modes of laser treatment altered these parameters and biocompatibility in diverse ways. Films of P(3HB) had water contact angle and surface energy of 92° and 30.8 mN/m, respectively, and average roughness of 144 nm. The water contact angle of copolymer films decreased to 80–56° and surface energy and roughness increased to 41–57 mN/m and 172–290 nm, respectively. Treatment in either mode resulted in different modifications of the films, depending on their composition and irradiation mode. Laser-treated P(3HB) films exhibited a decrease in water contact angle, which was more considerable after the treatment in the quasi-pulsed mode. Roughness parameters were changed by the treatment in both modes. Continuous wave line-by-line irradiation caused formation of sintered grooves on the film surface, which exhibited some change in water contact angle (76–80°) and reduced roughness parameters (to 40–45 mN/m) for most films. Treatment in the quasi-pulsed raster mode resulted in the formation of pits with no pronounced sintered regions on the film surface, a more considerably decreased water contact angle (to 67–76°), and increased roughness of most specimens. Colorimetric assay for assessing cell metabolic activity (MTT) in NIH 3T3 mouse fibroblast culture showed that the number of fibroblasts on the films treated in the continuous wave mode was somewhat lower; treatment in quasi-pulsed radiation mode caused an increase in the number of viable cells by a factor of 1.26 to 1.76, depending on PHA composition. This is an important result, offering an opportunity of targeted surface modification of PHA products aimed at preventing or facilitating cell attachment.

Studying the layer structure formation in laser additive manufacturing with AlMg6 alloy wire

When processing aluminum alloys with repeated laser radiation, which is typical for both multi-pass welding and additive manufacturing, volatile chemical components are being burnt. Due to the processing zone overheating if there are residual stresses, the probability of there being structural defects and deformations and, consequently, distortion of the final shape of the sample increases. Studies of the wall’s structure forming process during laser additive manufacturing with AlMg6 alloy wire, fulfilled based on experiments and computational methods, allowed us to obtain the necessary data for optimizing the process and determining the laser treatment modes. The simulation of the thermocyclic effect of laser radiation on the wall and the selection of mode parameters for the optimal structure of the material and the shape of the bead were performed. The results for the chemical composition of the final material, the number of defects and mechanical properties were quite satisfactory.

Investigation of the influence of laser treatment modes on coatings of aluminum, nickel, nickel-titanium systems

This paper shows the effect of different modes of laser treatment on the final structure of the coating obtained by the CS method. Among the studied modes, the following were selected: the speed of movement of the laser spot, defocused or focused laser beam, continuous or pulsed mode of laser treatment. The CS coatings of systems Ni, Ni-Ti, Al have been investigated. It is shown that under pulsed and defocused modes, the resulting coatings have cracks and other types of defects. It is also shown that the microhardness of CS coatings after laser treatment with a laser beam increases: 8 times for the Al system, 3 times for the Ni-Ti system, and does not increase for the Ni system.

Investigation of the intermetallic coating of the Ni-Fe system obtained by surface laser treatment on a steel substrate.

The article presents the results of a study of the Ni-Fe system coating on a 09G2S (Fe-Mn9% Si2%) steel substrate obtained by laser surface treatment. The coating was obtained in two stages. At the first stage, a precursor coating (PC) of Nickel was applied by cold spray (CS). At the second stage, its surface was laser treatment. The article shows changes in the composition and properties of the coating after laser treatment at different thicknesses of the precursor coating and different laser treatment modes. The results of the study showed that the composition and structure of the coating can be controlled by controlling the thickness of the precursor coating, the scanning speed, the scanning hatch, and the number of repeated scans.

Effect of laser treatment modes on metal surface marking color

The laser beam marking process is considered to be a subject to important scientific research. In this area, there are insufficiently studied problems and concepts requiring their experimental validation and determining the solutions. Upon laser action, the effect of metal surface coloration can be caused by different processes. The most probable is formation of thin oxidic films, although formation of the other compounds is not unlikely as well [1–2]. Under actual values of luminous flux density, however, scanning with laser beam results in occurrence of regular surface roughness. Therefore, the analysis of diffraction effect impact on the image color is also necessary [3–4]. The color images on the metal surface were assessed based on range of colors RAL “Reich Ausschluß für Lieferbedingungen”. In this system, the color space is divided to ranges with identification of each color by its unique index number. When doing research of the metal surface composite regular relief [5] obtained using laser marker, the depth of microroughnesses in differently colored samples was determined. The was performed using non-contact VICWU profilometer. Due to the method of measurement technological specificity, this equipment does not have destructive effect on the object under study. The roughness values (Rz and Ra) of the surfaces under study were measured based on acceptably small areas, thereat the base lines were selected in such way that to consider the surface waviness effect on the roughness values Rz and Ra [6]. The research results demonstrated that change of surface roughness values Ra and Rz by 1.5 times (owing to change of the surface laser treatment mode), changes the specimen metal surface coloration drastically.

Effects of laser treatment modes on the parameters of the hardening zones and the wear resistance of steel 40Cr

The paper presents the results of metallographic and tribological studies of laser hardening zones of steel samples. A full factorial experiment on laser hardening with a change in the distance from the focal plane, radiation power and processing speed was carried out. The regularities of changes in the depth and width of the quenching zones are obtained from the regression equations. With low-frequency transverse scanning of the laser beam up to 100 Hz, the hardening zones with a width of 20 mm and a depth of 1.4-2.0 mm in one pass were obtained. The wear resistance of the hardened zones is 3.68 times higher than the base material.

Strengthening of the Restored Surface Layer of Steel Parts 45 by Laser Boring

By means of the proposed technologies, the relationship and strengthening of the optimal modes of recovery of the restoring layer and the optimal laser treatment modes with bat-retaining straps are chosen. The microstructural, X-ray diffraction studies of the restored surfaces of the cams of the distributing shaft of the car were determined, the wear resistance and microhardness of the working surfaces were determined. By means of the proposed technologies of restoration and strengthening, optimum modes of applying the restoring layer and optimal modes of laser treatment (pumping energy of 20 kJ without melting of the surface) with bat-retaining coatings (thickness 2 mm) were chosen. The unevenness of the pulsed laser treatment with the restriction of the diameter of the laser spot and the treatment of a boron-rich surface layer with overlapping of the corresponding zones leads not only to the quenching but also to the release of individual local microparticles. New phases such as boron carbide, carbides - borides, iron borides, and others are formed. The strengthened surface layer has a complex structure and generally contains a martensite base with thin layers of borides, сarbides. The microhardness of the processing zone rises 3-4 times (Нμ 6500-7000 MPa).

Effect of Thermal Fields on the Structure of Corrosion-Resistant Steels Under Different Modes of Laser Treatment

The influence of temperature fields on the structure and properties of corrosion-resistant chromium steels under different modes of laser treatment is investigated. A model of heat transfer under laser impact on target is used to plot thermal fields and cycles and cooling rates. It is shown that the model used for computing thermal fields gives tentative geometric sizes of the fusion zones under laser treatment and selective laser fusion. The cooling rate is shown to have decisive influence on the structure of corrosion-resistant steels after laser treatment with surface fusion in devices for pulsed, continuous, and selective laser melting.

Design and Optimization of Steel Car Body Structures via Local Laser-Strengthening

Continuously rising demands of legislators require a significant reduction of CO2-emission and thus fuel consumption across all vehicle classes. In this context, lightweight construction materials and designs become a single most important factor. The main engineering challenge is to precisely adapt the material and component properties to the specific load situation. However, metallic car body structures using “Tailored blanks” or “Patchwork structures” meet these requirements only insufficiently, especially for complex load situations (like crash). An innovative approach has been developed to use laser beams to locally strengthen steel crash structures used in vehicle bodies. The method tailors the workpiece hardness and thus strength at selected locations to adjust the material properties for the expected load distribution. As a result, free designable 3D-strengthening-patterns surrounded by softer base metal zones can be realized by high power laser beams at high processing speed. The paper gives an overview of the realizable process window for different laser treatment modes using current high brilliant laser types. Furthermore, an efficient calculation model for determining the laser track properties (depth/width and flow curve) is shown. Based on that information, simultaneous FE modelling can be efficiently performed. Chassis components are both statically and cyclically loaded. Especially for these components, a modulation of the fatigue behavior by laser-treated structures has been investigated. Simulation and experimental results of optimized crash and deep drawing components with up to 55% improved level of performance are also illustrated.

ВЛИЯНИЕ МОЩНОСТИ ЛАЗЕРНОГО ИЗЛУЧЕНИЯ И СКОРОСТИ ДВИЖЕНИЯ ЛУЧА НА ГЕОМЕТРИЮ ЗОНЫ ОПЛАВЛЕНИЯ ПРИ ЛАЗЕРНОЙ ЗАКАЛКЕ СТАЛИ 40X

The improvement of operating characteristics of the working surfaces of machine parts, tooling and metal cutting tools is important for the modern industry. Laser hardening is one of the most intensively developing methods of improvement of friction surfaces wear resistance. Laser hardening of treated surface is possible from liquid or solid state. The largest values of depth and width of a hardened layer are achieved when laser hardening from the liquid state. The application of laser hardening with surface flashing is possible for a large range of body parts. In this regard, the study of hardened zones structure and the selection of modes that cause the maximum hardened layer characteristics are important for the implementation of laser hardening technology under factory conditions. The paper presents the results of experimental study of the influence of the emission power of the quasi-continuous fiber optic ytterbium laser and laser beam velocity on the geometry of 40H steel flashing zone, not including changes in heat-affected zone geometry. Using the LK-150/1500-QCW-AC laser emitter, the authors formed on the surface of 30105 mm samples the isolated thermal wake with distinctively noticeable fluxed zone and then studied the cross-section of this wake using the LaboMet-1 microscope. In the result of the study of fluxed zone cross-section geometric characteristics, the authors determined the treatment modes at which the fluxed zone cross-section appearance changed and defined its width and depth depending on the laser emission power. Laser treatment modes are defined when the largest difference between the fluxed zone depth and the depth of the crater formed on steel surface is achieved.

Creation of Submicroporous and Nanoporous Structures in Metallic Materials by Laser Thermocycling as Eutectic Is Reached

The possibilities of forming submicroporous and nanoporous structures in metallic materials by laser thermocycling as eutecticis reached were determined. With the implementation of the selected modes of laser treatment on L62 brass samples with a thickness of 50 µm leads to the formation of wrinkled relief, which indicates an increment of alloy volume in this area, that is, a porosity increment in the metallic material. Submicroporous and nanoporous structures are formed in the copper-zinc L62 alloy sample, which appear on the surface of the sample. Nanopores have a shape similar to equiaxial. Submicropores are formed as a result of nanopores merger. A relief is formed on the surface consisting of depressions having a shape similar to that of a hemisphere and a linear structure, oriented along the direction of rolling process.

ВЛИЯНИЕ РЕЖИМОВ ЛАЗЕРНОЙ МОДИФИКАЦИИ НА СТРУКТУРУ, СВОЙСТВА И ИЗНОСОСТОЙКОСТЬ МЕЛКОРАЗМЕРНОГО ИНСТРУМЕНТА ИЗ БЫСТРОРЕЖУЩЕЙ СТАЛИ Р6М5

The paper considers the issue of wear resistance improvement of small-sized cutting tools. One of the advanced ways to solve this problem is the heat treatment using the highly concentrated energy flows created by laser beam. Modern fiber optic lasers combine high power density of laser radiation with the possibility of laser beam delivery to the most hard-to-reach treated areas by using optic fiber. The study and forecasting of the properties and the structure of a modified zone are the most important elements of technological process preparing and allow selecting optimal modes of laser treatment. The paper gives the results of experimental study of the influence of laser modification parameters on the state and properties of the surface layer of the high-speed R6M5 steel samples. The authors obtained the dependences of heat-affected zone depth and width on the laser radiation power, measured the microhardness of various areas of treated surface and studied in details the structure obtained for various laser modification modes. The study revealed the increase in microhardness resulting from the fiber optic laser modification during the quasi-continuous operation and set the boundary between the modes of laser modification with flashing and without it for R6M5 tool steel. As the practical application of the results obtained, the authors carried out the evaluation of small-sized tools wear resistance according to the suggested modes and determined the laser modification modes allowing the increase of durability of small diameter twist drills in 5 and more times. Test results demonstrate the unavailability of some relevant modes for the tool working surfaces modification due to the extremely gross wear of the processed surface and the cutting edge damage within the cutting process.

Structure and Properties of Surface Layers of Sintered Powder Titanium VT1-0 After Laser Treatment

The effect of various modes of laser treatment of sintered powder titanium VT1-0 in an argon environment on the structure and properties of its surface is studied. It is shown that laser fusion of the surface reduces markedly the porosity in the fusion zone. One of the causes of elevation of the microhardness in the surface layers is growth in the total length of grain boundaries.

Use of Laser Heat Treatment for Creating Gradient Materials Based on the Fe – Cr – Ni System

The possibility of the use of laser radiation heating for making materials with specified distribution of ferro-and paramagnetic domains is studied. It is shown that application of plastic deformation with a high degree or reduction combined with subsequent laser heating in a specified temperature range to austenite-martensite alloys based on the Fe – Cr – Ni system produces materials with required distribution of regions of ferromagnetic martensite and paramagnetic austenite. The modes of laser treatment providing maximum strength of the formed austenite are determined.

Влияние лазерного облучения на электрохимическую активность TiO2

Lithium ions intercalation into the laser-exposed nanodisperse ТiO2 had been analyzed and its research results are given. The modes of laser treatment, when the degree of the «quest» load and, accordingly, specific energy capacity of the proper electrochemical current sources achieves a maximum, are experimentally set. Thermodynamical pecularities of current forming and lithium ions intrusion into the cathode material are set. Electrochemical source discharge capability analyzed in scope of laser-exposed ТiO2 using.