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A WC/Co-Cr coating was fabricated via laser cladding onto W18Cr4V high speed steel and its macroscopic morphology, phase composition, microstructure, microhardness and wear resistance were examined. The findings indicate that when the laser power is 1500 W, the powder feed rate is 20 g/min and the scanning velocity is 1.5 mm/s the laser clad layer is primarily composed of WC and WCo compounds, exhibiting minimal pores and cracks. The resulting microstructure is complex and characterized by a regional gradient distribution, containing WC, W2C, Fe2W2C, Fe3W3C, Co3W3C, Mo2V4C5, (Cr, Fe)7C3, and other complex phases. The hardness and wear resistance of the laser clad layer are significantly superior to those of high speed steel. The maximum hardness is exhibited within 0.3 mm from the surface of the laser clad layer, reaching 1361HV0.2 which is approximately 1.6 times that of the W18Cr4V high speed steel substate and the average wear amount is 70% of the W18Cr4V substate. After subjecting the laser clad layer to heat treatment at 450°C for 1 hour its wear resistance is further improved. The average wear of the laser clad layer is effectively reduced from 57.6 to 28.1 mg, which accounts for only 35% of the wear rate observed in the substrate. [ABSTRACT FROM AUTHOR]

Laser beam welding (LBW), laser cladding and selective laser melting (SLM) with metals without active substances such as O2 or S present poor processability. The most important reason for this is the negative surface tension coefficient leading to outward fluid flow inside the meltpool. In this work JG-3 Fe-based powder was clad onto 304 stainless steel and 7075 Al alloy substrates using a fibre laser. The fluid flow fields inside the meltpools of two materials with opposite surface tension coefficient were studied and a two-dimensional (2-D) axisymmetric numerical model was proposed. The Marangoni effect on fluid flow greatly influences the processing parameters and cladding effectiveness. The opposite surface tension coefficients of the 304 stainless steel and 7075 Al alloy brought about different fluid flow field inside the meltpool. The inward and outward fluid flow mode result in different meltpool morphology. The fluid flow mode affected by Marangoni effect and the process of the free surface motion. [ABSTRACT FROM AUTHOR]

A coating of the CoCrCu base powder was prepared on the surface of Ti-6Al-4V alloy by laser cladding/remelting with a fibre laser. The effect of the different melt materials such as Tribaloy, Cu and Si3N4 on the microstructure and wear resistance of these laser clad coatings were investigated. The CoCrCu laser clad coating had a good metallurgical bond with a Ti-6Al-4V alloy substrate and consisted primarily of TiC, Cu4Ti3, (Co, Cr)2Ti. The microhardness and wear resistance of this laser clad coating was increased over the as-received Ti-6Al-4V alloy due to the Cu base and the other intermetallics leading to second phase/the fine grain strengthening. A fine microstructure was obtained due to the remelting effect. [ABSTRACT FROM AUTHOR]

To improve the hardness and wear properties of 17-4PH martensitic stainless steel, used commonly to produce steam turbine blades, high speed laser cladding (HSLC) technology prepared the Fe-based WC ceramic composite coating on its surface. The relationship between laser power, microstructure and mechanical properties was judged by analysing the laser clad coating surface flatness, powder utilization rate, hardness and wear performance under different laser powers. The results showed that when the laser power was 2100 W, the scanning speed was 16 mm/s, the powder feed rate was 21.7 g/min and the overlap rate was 40%, the laser clad coating section was in a horizontal state and there were no unmelted powder particles. The powder utilization rate reaches the highest and the hardness reaches the maximum value of 433.02 HV0.5, about 1.27 times that of the 17-4PH stainless steel substrate. In addition, the wear performance is also the best. The observed improvements in hardness and wear resistance are due to the formation of hard strengthening phases such as WC and W2C, as well as the combined effect of fine grain strengthening and solid solution strengthening produced by M7C3 (M=Fe, Cr, W) carbides. [ABSTRACT FROM AUTHOR]

Multiscale microtextures were fabricated on the surface of TA1 foil using laser etching and laser shock imprinting (LSI) processes. First, laser etching process was employed to directly fabricate multiscale microtextures on the 20 µm thick TA1 foil as the laser etching workpiece. Then, using the same laser etching parameters, multiscale microtextures were processed on a 1 mm thick TA1 plate surface as the mould for LSI. Finally, the LSI was used to replicate similar multiscale microtextures from the mould surface, and the influence of pulse number and power density on the forming depth and replication degree of the TA1 workpiece was analysed. By comparing the aging effect and durability of the hydrophobic TA1 foils treated by laser etching and LSI processes, the differences in chemical composition stability and mechanical stability between laser etching and LSI surfaces were analysed. The laser etching surface exhibited a super-hydrophilic state within 12 hours and tended to be a superhydrophobic state after 30 days of storage in air. In contrast, no obvious aging effect was observed on the surface of the LSI samples, indicating better stability of surface wettability (110°

One of the well-known processes utilized in the modern business for permanently identifying products, including specifications and logo branding of any organization or institute, is laser marking. Little effort has been made to optimize the different geometrical characteristics of laser marked surfaces which is needed for applications in laser marking of any product identity. In this work efforts were made to develop the mathematical model of the responses, analyse the parametric influence on the marking characteristics and to find the optimal setting of process variables for marking the surface of 304 stainless steel using a fibre laser with a beam spot diameter of 21 µm. The single- and multi-objective optimization were carried out on the responses using desirability function analysis. Results revealed that for multi-objective optimization a laser power of 10.6 W, duty cycle of 56.86%, scan rate of 7 mm/s and pulse rate of 60 kHz should be set for more advantageous marking features for marking a triangular shape. [ABSTRACT FROM AUTHOR]

The Fe-(TiC, Mo) composite coating was laser clad onto the surface of Q235 steel, and the study delved into the impact of (TiC, Mo) content (x) on the coating’s microstructure, microhardness, wear resistance and corrosion resistance. The results revealed that as x varied from 0 to 10, 20 and 30 wt.%, the phase composition shifted from α-Fe to α-Fe+γ-Fe+TiC. This transition was accompanied by a constant variation in the proportion of different phases, with a continuous increase in in situ TiC particle content. The microhardness, wear resistance, and corrosion resistance of the coating displayed an initial increase followed by a subsequent decrease with the increase in x, reaching their optimal values at 20 wt.%. This enhancement in microhardness and wear resistance, up by 4.34 and 8.27 times, respectively, can be attributed to fine crystal strengthening, dispersion strengthening, and solid solution strengthening. Furthermore, the incorporation of (TiC, Mo) in the coating facilitated the formation of a dense and uniform passivation film, while grain refinement mitigated the galvanic corrosion effect. As a result, the coating exhibited remarkable corrosion resistance. [ABSTRACT FROM AUTHOR]

Laser-directed energy deposition (LDED) has the advantages of high material utilization, high degrees of freedom and high forming efficiency; consequently, it is applied widely in surface enhancement and repair of damaged parts. There are, however, some defects in the deposition process such as cracks and pores. The assistance of the external energy field is an effective measure to reduce such defects. To study this we deposited a single track clad of Inconel 625 onto the surface of HT300 grey cast iron by laser-directed energy deposition (LDED) with electromagnetic compound field (EMCF) assistance. The geometrical characteristics, microstructure and microhardness of the clad were determined to investigate the influence of the EMCF. The results show that: under the action of the EMCF with high magnetic field strength and high pulse current strength, the geometrical characteristic of the clad changed markedly. The application of the EMCF led to an increase in clad depth and a decrease in clad height, which led to an increase in dilution rate. The geometrical characteristic did not change significantly when the EMCF was small. The application of the EMCF can inhibit the growth of dendrites crystals, facilitates fine grain formation and improves the uniformity of microstructure. The microhardness improved and the range of microhardness decreased significantly under the condition of the EMCF. [ABSTRACT FROM AUTHOR]

A fibre laser was used to weld Q345D/20Mn2 dissimilar steel with and without a Ni60 powder filler. Finite element (FE) simulation of the temperature and stress fields in the laser beam welding (LBW) was conducted COMSOL. Experimental investigation determined the effect of Ni-based powder filled welding on the microstructure, morphology, element content, microhardness and fracture morphology of the weld cross-section. The results show that when the laser power was 2700 W, the scanning speed was 1 mm/s and the out-of-focus amount was 0 mm, the tensile properties of Q345D/20Mn2 steel welds were optimal and deformation was minimal. Under such conditions the depth of the weld pool can reach 2.7 mm and the width 2.8 mm. After the Ni-based powder melts and penetrates the bottom of the base material (BM) along the weld seam, small cytosolic, equiaxed and columnar crystal grains can be observed near the fusion line, and the Ni-based filler powder can achieve a good metallurgical bond with the BM. The location of tensile fracture is at the weld and small tough nests can be observed in the cross-section leading to judgment that the fracture mode is ductile. [ABSTRACT FROM AUTHOR]

To prepare a high quality Fe-based ceramic composite coating, 17-4ph+30% WC alloy powder was clad onto a 17-4ph stainless steel substrate by high speed laser cladding (HSLC) and a metal matrix composite (MMC) clad without cracks and pores was achieved. The WC particle distribution, microstructure formation and evolution mechanism of the MMC laser clad were studied in detail. The results show that the phase composition of the MMC laser clad mainly includes γ-Fe, W2C, WC, Ni3Fe, Cr23C6, etc. The WC particles in the MMC laser clad show a good metallurgical bonding with the 17-4ph substrate, the dilution rate of the clad is low and the higher heat input causes more WC particles to melt and decompose, generating more hard strengthening phases. The grain refinement strengthening, solid solution strengthening and second phase strengthening are more prominent, which provides a scientific basis for optimizing the preparation of high quality Fe-based ceramic composite coatings. [ABSTRACT FROM AUTHOR]

In order to solve the problem of insufficient hardness and friction wear performance of Ni-based coatings under certain extreme working conditions, this paper designs experiments from a process perspective to study the effects of laser scanning method and overlap rate on the microstructure and properties of laser clad Ni60-WC composite coatings. Unlike previous studies, this study considers the comprehensive effects of laser scanning method and overlap rate on coating performance for specific laser clad layers, rather than just one of them. The results show that the performance of the coating after fusion is the best in the single line scanning mode and the overlap rate is within the range of 30 to 35%. The maximum hardness of the laser clad coating can reach 1216 HV, which is 1.08 to 1.43 times the 850 to 1150 HV hardness of the Ni-WC coating reported so far. The wear resistance of the laser clad coating has also been improved to some extent. The results confirm the phenomenon of interactive influence between scanning mode and overlap rate in the laser cladding process, which will provide a new 4knowledge for optimizing laser cladding in the future. [ABSTRACT FROM AUTHOR]

In this study, a comprehensive analysis of the lanthanide doping effect on the possibility of producing Bragg resonators using a UV excimer laser is presented. To fabricate the optical fibre preform, modified chemical vapour deposition (MCVD) technology equipped with a doping system using organometallic lanthanide compounds produced by Optocore was used. The efficiency of the fibre Bragg grating (FBG) inscription process was examined. Inscription of gratings was performed using manufactured fibre subjected and not subjected to hydrogen loading. The changes in three parameters characterizing the FBG spectra during exposure to the UV laser beam were determined. The efficiency of grating inscription on the produced lanthanide-doped fibres was compared to those on SMF-28 and NUFERN GF1 fibres. Since the spectral response is a key parameter determining the possibility of using FBGs for fibre laser construction, the temperature sensitivity for FBGs inscribed in the considered fibres was determined. [ABSTRACT FROM AUTHOR]

Through simulation based on the Workbench platform in ANSYS the optimal laser remelting process parameters were identified to achieve the maximum performance of a Ni60 coating laser clad onto a H13 steel surface. Laser remelting with a fibre laser was conducted according to the optimal process parameters obtained and the coating morphology, microstructure and microhardness after remelting were analysed. The results show that when the laser power was 1200 W and the scanning speed was 4 mm/s the remelted coating has the smallest residual stress value, pores in the coating were basically eliminated, the organization was dense, the hardness improved and the coating quality was the best. When the laser power was 900 W and the scanning speed was 2 mm/s the maximum residual stress value of the remelted coating was slightly smaller than that of the un-remelted coating, the coating morphology quality was better, and there were very few bubbles. [ABSTRACT FROM AUTHOR]

The coal mine roller is a key component in the mine belt conveyor system. The work described herein involved a Fe-based clad prepared on a 42CrMo steel roller substrate by laser cladding in order to improve the service life and performance of the coal mine roller. The chemical composition, microstructure, properties, microhardness, wear resistance and salt spray corrosion performance of the laser clad layer and substrate under the optimum process parameters were systematically studied. The results showed that laser scanning speed and laser power mainly affect the width, height and depth of the clad. The process parameters were optimized by a series of orthogonal experiments. The optimal process parameters were a laser power of 1700 W, scanning speed of 6 mm/s and powder feed rate of 15 g/min. The laser clad mainly composed γ-Fe and the compounds of Fe and Cr, such as CrFe4and CrFe19. Along the depth direction of laser clad the microstructure gradually changed from planar crystal and bits of dendrite crystal to equiaxed crystal. The grains at the top of the direction of the laser cladding layer were further refined. The hardness of the laser clad was increased by about 2.2 times that of the substrate. The friction and the loss of weight from wear test and salt spray corrosion of the laser clad show that the weight gain is much smaller than that of the substrate. The experimental results show that the wear resistance and corrosion resistance are improved significantly. [ABSTRACT FROM AUTHOR]

Studies have shown that unconventional machining offers advantages when it comes to machining ceramics in the form of higher material removal rate (MRR) and better surface finish. This present study focuses on the experimental investigations using a fibre laser to cut 7 mm thick ceramic plates used as glazed floor tiles. It involved a systematic experimental study to determine the relationships between process parameters and machining characteristics. Based on the experimental results, regression equations are developed to estimate the responses as functions of the laser process parameters and gas pressure. The developed regression equations are then used in a particle swarm optimization (PSO) technique with a MATLAB algorithm to minimize glass formation and taper angle in the cutting region which, in turn, improves productivity and surface finish. The optimal parameters of the process are found based on the minimization of the taper angle with relatively low operating energy cost. [ABSTRACT FROM AUTHOR]

Due to their outstanding corrosion resistance, mechanical characteristics and low specific density, AA5083 and AA6061-T6 Al alloys are used in the aerospace, automotive and marine sectors. Joining such dissimilar Al alloys using conventional fusion welding techniques is very challenging. In contrast, laser beam welding (LBW) is a non-conventional welding technique that is promising to weld dissimilar materials. The viability of welding dissimilar AA5083 and AA6061-T6 joints using fibre laser welding are examined herein. The effect of laser power and welding speed on the morphological, microstructural, microhardness and tensile strength of the welded joints was assessed and revealed that increasing welding power resulted in deeper keyhole penetration. Microporosities were formed due to Mg evaporation and shrinkages; however, the existence of these porosities did not show significant effect on the tensile strength. The microhardness values indicate that the welds were harder than the AA6061 and AA5083 base metals. This is explained by the existence of Mg2Si phase in the AA5083-AA6061 dissimilar junction in addition to the grain size circumstances. The fracture examination showed brittle fracture pattern that is regarded to the formation of brittle intermetallic compound (IMC) phases of Mg2Si, in addition to the inter-dendritic brittle phases of other sites as they were frequently inter-granular. [ABSTRACT FROM AUTHOR]

In view of the difficulties such as coarse microstructure, performance degradation and excessive residual stress during the preparation of Ti-6Al-4V layers by laser cladding, the microstructure and mechanical properties of such a Ti-6Al-4V coating were optimized and improved based on the plastic deformation effect caused by laser shock peening (LSP). The characteristics of phase composition, changes in microstructure and morphology, grain plastic deformation and the influence of mechanical properties of the laser clad Ti-6Al-4V coating were studied pre- and post-LSP. The results indicate that the α/α' phase content increases and the β phase content decreases after LSP. The β phase and acicular martensite α' phase is refined significantly and divided, and the basket structure presents a more dense and staggered distribution after LSP. Laser cladding causes the grains in the Ti-6Al-4V coating to undergo plastic strain and the degree of grain refinement was significantly improved following LSP. The microhardness at the top of the laser clad Ti-6Al-4V coating increases from 23 to 30% compared after LSP. At the same time, the LSP promotes the transformation of residual tensile stress to compressive stress on the surface of the laser clad Ti-6Al-4V coating, with an average residual compressive stress value of about 339 MPa. This study provides theoretical and methodological references for optimizing the microstructure and properties of Ti-6Al-4V coatings. [ABSTRACT FROM AUTHOR]

Silver alloys are often used for electrical switches in railway transportation. However, a well-known issue with these switches is their relatively short application period due to certain disadvantages of silver alloys, mainly their low hardness and low resistance to abrasive wear, in contrast to their excellent electrical conductivity. Therefore, the main goal of this study was to increase or maintain the hardness of the surface layer in order to extend the life of worn parts without compromising their electrical properties. Instead of ceramic particles, as in other studies, metallic powders were used, which could increase the electrical and/or thermal properties of silver alloys. The following work presents the use of laser processing as a relatively new technique for metal and metal alloy surface processing technology. In particular, a process based on the melting of silver (Ag) with metallic powders, such as chromium (Cr) and nickel (Ni) particles, is presented. The aim was for these powders to create intermetallic phases with a silver matrix in the obtained surface layer, significantly improving the mechanical properties based on the formation of the phases coherent or semi-coherent with the silver matrix. Regarding the original practical implications of this work, it was important to investigate the possibility of applying fibre laser for surface property enhancement. The scientific aim was to describe the changes in microstructure and compounds that occurred in the laser-remelted surface silver layer after Ni and Cr particles were fed into the basic silver material. It was concluded that the surface layer obtained after chromium application was without cracks and defects and had a higher hardness than the untreated material. A three-zone structure was also found in the obtained surface layer: (1) the remelted zone, (2) the heat-affected zone, and (3) the matrix material. The remelting zone revealed a higher hardness compared to the untreated material, reaching 92 HV0.3, which is more than twice the initial hardness value. [ABSTRACT FROM AUTHOR]

The effect of Ni content on the microstructure and properties of an ultra- fine grained (UFG) Fe-based layer clad onto a Q235 steel with a fibre laser was examined. The results revealed that within the range of 0 to 6 wt.% Ni, each Fe-based UFG laser clad layer consisted of α-Fe, γ and in situ synthesized VC. As the Ni content increased so the grain size of the Fe-based UFG laser clad layer matrix and the amount of retained austenite also increased. The microhardness of the Fe-based UFG laser clad layers initially decreased and then increased with the addition of Ni. The corrosion resistance of the Fe-based UFG laser clad layers exhibited an increasing trend followed by a decreasing trend. Notably, when the Ni content ranged from 4.5 to 5.2%, the Fe-based UFG laser clad layer demonstrated excellent comprehensive performance, including outstanding corrosion resistance and microhardness. [ABSTRACT FROM AUTHOR]

Ni-60%WC coatings were deposited on H13 steel substrate by laser cladding with a fibre laser. The microstructure, microhardness and wear performance of the obtained laser cladded Ni-60%WC coatings and the effect of laser power on the coefficient of friction (COF) and wear rates were analyzed. The results show that the microstructure of laser cladded Ni-60%WC coatings is mainly composed of WC and γ-Ni solid solution phases, and the hardness is decreased with an increase in laser power. The average COFs of laser cladded Ni-60%WC coatings deposited at laser power of 2100, 2500 and 2900 W are 0.51, 0.52 and 0.53, respectively; and the corresponding wear rates are 40.40 x 10-6, 86.20 x 10-6 and 120.25 x 10-6 mm³/Nm, respectively. From this it can be said that the laser power of 2100 W presents as the optimum in terms of wear resistance. The WC hard phase in the laser cladded Ni-60%WC coatings reduces the plastic deformation caused by the tribo-pair, and the wear mechanism is dominated by abrasive wear, accompanied with adhesive wear. [ABSTRACT FROM AUTHOR]

Laser marking is the process to mark an image by utilizing laser thermal energy used primarily for product identifications and traceability. It is versatile and well known process employed by the manufacturers to mark various materials. The mark produced by a fibre laser beam produces one of the fine marking components and it is well accepted form of marking used nowadays. The research paper revealed that laser beam marking quality is the function of various input controlling factors like laser spot size, transverse feed, scan rate, laser power which had a significant impact on quality attributes. The paper focuses on the creation of better quality equilateral triangular-shaped laser inscribed image on grade 304 stainless steel surface in a shortest possible time. The process variables involved in the present study includes pulse rate, duty cycle, laser power, and scan rate which were varied one at a time for obtaining better marking quality characteristics like high mark quality, closer to target mark angle and less deviation of marked area. The observed results revealed that pulse rate of 50 kHz, laser power of 12.5 W, scan rate of 35 mm/s and duty cycle of 99% provides better marking quality. [ABSTRACT FROM AUTHOR]

The circularity of the drilled hole at the top and bottom surfaces of the plate, as well as the taper angle of the drilled hole, are important characteristics in drilling that have a significant impact on the quality of a drilled hole. In this present study the laser trepanning drilling process is carried out on 7 mm thick glazed ceramic tiles using a fibre laser. The study investigates the effects of laser process parameters; namely, laser power, scanning speed, frequency and number of trepanning passes on the hole diameter at the top and bottom surfaces of the ceramic tile, the circularity of the hole at the top and bottom surface and the taper angle of the drilled hole. The effects of gas pressure and hole diameter on the hole characteristics are also investigated. It is observed that the circularity of the hole at the top surface increases with an increase in laser power, gas pressure, and hole diameter, whereas the circularity of the hole at the bottom surface decreases with an increase in laser power and scanning speed. It is also observed that the taper angle of the drilled hole increases with an increase in laser power, gas pressure and hole diameter. It is seen that the hole diameters on the top surface of the plate do not get much affected when the trepanning passes are increased. [ABSTRACT FROM AUTHOR]

Methods of output wavelength tuning in short-pulsed fibre lasers are analysed. Many of them rely on spectral selection principles long used in other types of lasers. For compatibility with the fibre-optical format, the corresponding elements are sealed in compact, airtight volumes with fibre-optical radiation input and output. A conclusion is presented about the relatively small number of inherently "fibre-optical" ways of tuning the wavelength of radiation. It is demonstrated that the range of output wavelength tuning in short-pulsed fibre lasers may span hundreds of nanometres (even without extension beyond the active medium gain contour through nonlinear effects). From the presented review results, it may be concluded that the search for the optimal tuning method complying with the user-preferred all-PM-fibre short-pulsed laser design is not yet complete. [ABSTRACT FROM AUTHOR]

Laser metal deposition (LMD) technology was adapted to fabricate 7075 Al alloy (AA7075) parts on T6-state rolled plates with a fibre laser system. Thereafter the optimal laser power parameters were explored. The results indicated that the microstructure of the AA7075 by LMD consisted of equiaxed grains, and the laser power of 1.1 kW yielded the minimum defects and superior mechanical performance; however, the deposited sample has low strength and poor ductility, with a mixed fracture mode of brittle fracture, ductile fracture, and intergranular fracture. [ABSTRACT FROM AUTHOR]

This study developed a set of custom made laser remanufacturing equipment for deep penetration laser cladding and remelting tailored to the particular demands of the TC4 alloy. The yield strength improved to 865 MPa after laser cladding and the strength should be a good approximation to substrate. The yield strength was increased to 878 MPa by deep penetration laser remelting in a modified atmosphere. The experimental results of this method demonstrate the effectiveness of deep penetration laser remelting in remanufacturing and its potential to adapt to a wide range of part defects. This study demonstrated that the mechanical strength of TC4 alloy could be enhanced by deep penetration laser cladding and remelting. [ABSTRACT FROM AUTHOR]

The effect of fibre laser surface treatment with different energy densities on the surface microstructure and bonding performance of a carbon fibre reinforced polymer (CFRP) composite was investigated. Results indicate that the effect of laser surface treatment on the CFRP with a defocusing amount of 4 mm is the optimal. With increasing energy density the resinremoval degree of the CFRP structure surface increases gradually, the surface free energy of CFRP greatly increases and the contact angle of CFRP decreases. At the same time, the high energy density will lead to the fibre being easily damaged. A combined mechanism of laser treatment on CFRP is discussed. [ABSTRACT FROM AUTHOR]

CuSn8Ni alloy powders were deposited on the low carbon steel plate by laser cladding technology to prepare a CuSn8Ni/ST37-2G steel bimetallic bearing material. Microstructure, microhardness, and interfacial elemental diffusion of the CuSn8Ni laser clad coating were investigated. The optimum process parameters for laser cladding the CuSn8Ni alloy were obtained. The results showed that when the laser power was 1300 W, scanning speed was 8 mm/s and the powder feed speed was 0.5 rpm, the CuSn8Ni laser clad layer had an excellent metallurgical bond with the matrix and had no apparent defects. The laser clad layer had a dendritic microstructure. It mainly consisted of Sn-containing a-Cu solid solution and interdendritic (a+d) eutectoid. Cu and Fe elements had significant element diffusion behaviours, and the diffusion distance was about 1 to 2 µm. The average hardness of the coating was 128.6 HV, twice that of the traditional Cu-Pb bearing material. [ABSTRACT FROM AUTHOR]

Few reports are focused on the relationship between corrosion resistance and grain size of second phase reinforced metal matrix composite (MMC) materials. This study successfully prepared a submicron ultrafine grained (Ti-V)C/Fe composite layer by simultaneously regulating the laser cladding process parameters and the alloy powder particle size. The regression relationship between the layer's corrosion current density, Icorr, percentage of (Ti-V)C, PC, and grain size of carbides, dC and layer's matrix, dFe was established, that is Icorr=22.53+1708.47PCdC-76.92dFe µA/cm². As the average grain size of Ti-V carbides increases or the Febased layer matrix decreases, the corrosion current density of the composite layer increases and vice versa. The results of immersion tests confirmed that the smaller the (Ti-V)C particles, the better the corrosion resistance of layers. Also, the smaller the layer matrix grains, the more the preferential corrosion at the grain boundary, more favourably forming a corrosion product film. [ABSTRACT FROM AUTHOR]

The impact of the heat treatments on the microstructure, high temperature hardness and wear performance at room and elevated temperature on a IN718 alloy fabricated via laser metal deposition (LMD) is investigated. It was found that the microhardness of the laser deposited IN718 alloy under different heat treatment conditions decreases with the increase of test temperature. Under various heat treatment conditions the wear rate of the laser deposited IN718 alloy at high temperatures is lower than that at room temperature. At room temperature the wear rate of the as-deposited IN718 alloy is higher than that of the heat treated samples. In contrast, at elevated temperatures the wear rate of the as-deposited IN718 alloy is lower than that of the heat treated samples. [ABSTRACT FROM AUTHOR]

A method for the prediction of surface texture morphology after the laser surface texturing (LST) of a biomimetic sinusoidal texture based on scallop shells was established. The method was based on the back-propagation (BP) neural network optimized using hybrid metaheuristic algorithms. The number of scanning times, pulse frequency, laser power and scanning speed were used as input parameters, while the texture morphology parameters were used as the output parameters. A hybrid approach combining the genetic algorithm (GA) and particle swarm optimization (PSO), which complemented the advantages of both algorithms, was applied to optimize the BP neural network (GA-PSO-BP). The resulting model was then compared to two traditional neural networks, GA-BP and PSO-BP neural networks, and its prediction accuracy was evaluated using several different metrics. Metrics included the maximum relative error (MRE), mean absolute error (MAE), root mean square error (RMSE), and mean absolute percentage error (MAPE). The results have shown that the GA-PSO-BP neural network has better prediction performance of the texture width and depth in terms of lower error, while also being more stable. Such behaviour demonstrated that the established GA-PSO-BP neural network can be a powerful tool for predicting the sinusoidal texture morphology parameters obtained in laser processing. [ABSTRACT FROM AUTHOR]

Laser powder bed fusion (LPBF) is used as an additive manufacturing (AM) technique to fabricate complex structures. In this study an orthogonal response surface test was designed to optimize the relative density of an 18Ni300 maraging steel sample fabricated through LPBF. The results demonstrated that the influence of the process parameters on the relative density of the maraging steel sample decreased in the order of laser power > scanning speed > hatch spacing. At a laser power of 150 W, scanning speed of 793.658 mm/s, and hatch spacing of 65 µm, the relative density of the sample was 99.797%, which was consistent with the theoretical relative density of 99.80% predicted by the multivariate linear binary regression model and higher than the relative density of 99.13% optimized through the orthogonal test. The ultimate tensile strength of the sample was 1.43 GPa, which is higher than that optimized through the orthogonal test. In addition, the surface of the sample was smoother and flatter, the melt track more continuous and regular, and the pores fewer in number as compared to unoptimized sample. [ABSTRACT FROM AUTHOR]

By monitoring the surface temperature of a carbon fibre reinforced polymer (CFRP) sample, we designed a wet laser cleaning method to successfully remove the paint and surface epoxy resin layer without damaging the CFRP substrate. The temperature and stress distributions at the interface between the epoxy resin and CFRP were simulated by the heat conduction equation. The variation trend of temperature and stress with the average laser power was obtained and the cleaning threshold was given. A 1064 nm acoustic-optical Q-switched laser was used for cleaning by scanning the painted CFRP sample at a certain speed with different laser powers and the cleaning effect was monitored by measuring the temperature in real-time. The cleaning mechanism in the wet laser cleaning of CFRP is indicated to be the thermal stress stripping mechanism. [ABSTRACT FROM AUTHOR]

Ni-60%WC alloy coatings were prepared on the surface of a H13 steel substrate by laser cladding with a fibre laser at different laser powers. The microstructure and phases of the laser clad Ni-60%WC alloy coatings fabricated with laser power of 2100, 2500 and 2900 W were analyzed, and the electrochemical performance was measured by the potentiodynamic polarization curve (PPC) and electrochemical impedance spectroscopy (EIS). The results showed that the laser clad Ni-60%WC alloy coatings were composed of WC, W2C, and NiC phases, and the WC particles were homogeneously distributed throughout the coating cross-sections to form sound metallurgical bonding with the H13 steel substrate. The corrosion current density icorr, and polarization resistance Rp, were lowest on the laser clad Ni-60%WC alloy coating fabricated with a laser power of 2500 W. The impedance of this sample also exhibited the largest, demonstrating that the appropriate laser power will improve corrosion resistance. [ABSTRACT FROM AUTHOR]

Additive manufacturing (AM) is one of the most important and, of course, the most attractive technologies that has attracted the attention of industries and researchers in the last few decades. The direct laser metal deposition (DLMD) method is one of the AM methods that can be used to produce metal parts with good dimensional accuracy and quality. In this research the effect of laser power on the geometrical dimensions and microhardness of 316L stainless teel single-track layers additively manufactured by the DLMD method onto a 4130 steel substrate was studied. In addition, the microstructure of the 316L stainless steel DLMD layers was investigated. The height and the maximum width of the 316L stainless steel DLMD layer, the width of the interface, penetration depth, and microhardness characteristics of the 316L stainless DLMD single-track layers were considered as output responses. The results showed that by increasing the laser power, the height, maximum width of the 316L stainless steel DLMD layer, width of the interface, and penetration depth of the 316L stainless DLMD single-track layers increased. At the maximum laser power of 260 W the maximum height and maximum width of the 316L stainless steel DLMD layer and width of the interface of the 316L stainless steel DLMD layers were obtained at 830, 970 and 615 µm, respectively. The microhardness of the samples varied from 281 to 314 HV. Examination of the microstructure of the 316L stainless steel DLMD layers showed solidification in columnar and equiaxed dendritic structures in all parts of the single-track layers, with the formation of secondary phases in the interdendritic regions. [ABSTRACT FROM AUTHOR]

Al-Si coatings have been widely used for their low density and high strength-to-weight ratio in automobile industries; however, poor tribological such as low wear limits their applications. The development of surface modified Al-Si coatings to enhance the tribological properties is essential and so herein is presented an investigation of the effect of laser parameters on the wear performance of Al-Si-carbon nanotube (CNT) coatings deposited on AA7075 alloy substrates. Al-Si-CNT coatings were deposited on the AA7075 substrate using atmospheric plasma spraying (APS) and then subject the laser surface modification (LSM) with a nanosecond pulsed fibre laser. Wear tests were carried out under dry conditions to evaluate wear rate and coefficient of friction (COF). The laser operating parameters like laser power, scanning speed and line spacing were optimized using multi-objective optimization to achieve minimum wear rate and COF. [ABSTRACT FROM AUTHOR]

A hydrophobic Cu foil surface with microgroove textures was prepared by laser shock imprinting (LSI). First, a micromould with groove features is prepared by laser marking, and then the microgroove textures on the micromould are copied to the workpiece surface by LSI. The hydrophobic Cu surface was subjected to fluorination modification treatment, and it was found that self-assembled monolayers (SAMs) were formed on the surface, which enhanced the surface roughness and reduced the surface free energy. Then, the effects of different ablative medium thickness, laser energy and workpiece thickness on the surface morphology and static contact angle of the workpiece surface were studied. When the thickness of the ablative medium is 40 μm, no breakdown occurs. When the laser energy increases from 565 to 1690 mJ and the workpiece thickness decreases from 150 μm to 80 μm, the degree of replication of microtextures on the workpiece surface gradually increases. Meanwhile, the static contact angle of the surface increases, and the hydrophobicity increases. The acid resistance and alkali resistance of the hydrophobic Cu surface prepared by the LSI process were systematically studied. By observing the microtexture morphology and measuring the element composition of the workpiece, It was found that the hydrophobic surface was still hydrophobic after being immersed in HCl solution of pH=2 and NaOH solution of pH=12 for 24 hours, which shows that the hydrophobic surface prepared by LSI has good acid resistance and alkali resistance. [ABSTRACT FROM AUTHOR]

Rare-earth-doped optical fibres are widely used in lasers and amplifiers. The incorporation of ytterbium and aluminium oxide in a high doping concentration has led to the fabrication of a multi-mode (MM) optical fibre. Within this research, the design, preparation and calculation for the production of a fibre with a targeted 45 μm core diameter are explored. By Energy Dispersive X-ray (EDX) analysis, the doping concentrations of the elements in the core have been measured as 60.4 at.% Al and 1 at.% Yb. Supporting micrographs are used for confirming the core/cladding ratio. Based on the atomic percentage concentration, the calculated refractive index of the multi-element core has an n = 1.61 and an NA = 0.678. Characterisation of the fibre, including absorption and emission cross-section analysis, was performed in order to prove the ability of the fibre to be used for amplification as well as lasing applications. [ABSTRACT FROM AUTHOR]

Laser material processing has diverse applications in the manufacturing industries. The efficiency of laser material processing depends on the interaction of the laser beam with workpiece material. This study investigates the effect of different coating conditions (graphite spray and black spray paint) on the mild steel worksheet surface during the laser bending process. The uncoated condition is compared with the coated conditions in terms of average maximum temperature at the top surface and bend angle. The average maximum temperature at the top surface and bend angle generated in all three coating conditions are analysed for single and multi-scan laser bending. The temperature and bend angle is increased by applying graphite coating than in the uncoated condition, whereas no significant variation is observed for black spray paint, during single scan laser bending. In multi-scan laser bending the temperature is increased steadily except for the graphite coating, and insignificant variation in bend angle is observed among different coating conditions. [ABSTRACT FROM AUTHOR]

Laser transformation hardening (LTH) is the efficient method of surface hardening used for synthesizing a hard, wear resistant surface layer on parts through the ultrafast heating action of the high energy scanned laser beam. Initial microstructure plays a very significant role on nucleation and growth kinetics of austenite formation during ultrafast heating of laser treatment. The conventional hardening and tempering heat treatment can produce very interesting microstructure as initial microstructure for LTH. In this work the effect of the tempered structure as the initial structure on LTH 8620 steel was investigated. It was observed that initial tempered structure significantly affects the surface hardness and hardening depth after LTH. It was observed that microstructure containing more martensitic features and lesser carbides produces coarser martensitic structure with shallow hardened case depths. On the other hand, microstructure containing more ferritic structure and high-volume fraction of carbides showed finer martensite with deeper hardened case depths. LTH of all tempered specimens shows that with increase in tempering temperature surface hardness decreases. As compared to conventional hardening by quenching, it was observed that surface hardness increased by 52 to 128% for LTH. After LTH about 15 to 22% drop in surface hardness was observed with increase in tempering temperature for different scanning speeds. On the other hand, laser transformation hardened depth and laser transformation hardened width are observed to rise for all scanning velocities with tempering temperature. After LTH, laser transformation hardened depth is observed to increase by 18 to 24% whereas laser transformation hardened width is observed to rise by 12 to 43% when tempering temperature is raised from 205 to 705°C. [ABSTRACT FROM AUTHOR]

Non-traditional micromachining methods such as laser micromachining and micro-electrical discharge machining (µ-EDM) are applied to generate intricate shapes and hard-to-cut materials without direct contact. Although both have advantages and limitations, laser micromachining is faster while µ-EDM yields high surface quality. This results in challenges to choosing the right method for a specific application, with the sequence of machining being crucial. This work discusses the benefits and downsides of each method and highlights improvements to the machining conditions. The study examined the variation in material composition before and after micromachining with µ-EDM and fibre laser micromachining and found that material composition varied markedly with laser micromachining, while there was barely any change when µ-EDM was used. µ-EDM resulted in better circularity with a minimum value of 0.00116 mm compared with 0.0169 mm obtained with laser micromachining. Laser micromachining resulted in a greater material removal rate (MRR) and heat affected zone (HAZ) than with µ-EDM. Of significance, it was found that adulteration of the EDM tool material onto the workpiece occurred with µ-EDM; this did not occur with laser micromachining on account of its non-contact nature. [ABSTRACT FROM AUTHOR]

Laser bending is an advanced manufacturing process used for precise bending of a wide range of materials. The process is limited to attain a small bend angle and low production rate. This study is attempted to overcome these problems by applying forced cooling at the bottom surface during multi-scan laser bending of an Al sheet. The bend angle and temperature of the top surface are analysed in both natural and forced cooling conditions at different laser power and scanning speed in each scan. It is found that the temperature reduces with the number of scans in both the conditions. The bend angle is found to be enhanced and melting is reduced in forced cooling than natural cooling. forced cooling is found to be more effective at high laser power, low scanning speed and high number of scans. The outcomes of the study are beneficial for manufacturing industries, looking to enhance the bend angle and reduce the production time by reducing the number of scans required for attaining a certain bend angle. [ABSTRACT FROM AUTHOR]

In the present paper, different surface preparations are investigated with the aim of increasing the wear behaviour of an electrophoretic graphene coating on a copper plate. The study was divided into two steps: In the first step (pre-tests), to detect the most promising pretreatment technology, five different surface preparations were investigated (electropolishing, sandblasting, degreasing and pickling, laser cleaning and laser dots).In the second step, on the basis of the results of the first step, a 32 full factorial plan was developed and tested; three treatment types (pickled and degreased, laser-cleaned, and laser dots) and three different voltages (30, 45 and 60 V) were adopted. Analysis of variance (ANOVA) was used to evaluate their influence on wear resistance; in particular, the maximum depth and width of the wear tracks and the coating break distance were investigated. The results of this study show that, in optimal conditions, laser treatment (particularly laser dots) canlead to as high as a four-fold increase in wear resistance. [ABSTRACT FROM AUTHOR]

Building upon recent advances in GaSb-based diode lasers and Er-doped fluoride fibre technologies, this article demonstrates for the first time the fibre-based amplification of mid-infrared diode lasers in the wavelength range around 2.78 $\mu$m. The laser setup consists of a GaSb-based diode laser and a single-stage Er-doped fibre amplifier. Amplification is investigated for continuous wave (CW) and ns-pulsed input signals, generated by gain-modulation of the GaSb-based seed lasers. The experimental results include the demonstration of output powers up to 0.9 W, pulse durations as short as 20 ns, and pulse repetition rates up to 1 MHz. Additionally, the amplification of commercial and custom-made GaSb-based seed lasers is compared and the impact of different fibre end-cap materials on laser performance is analysed.

WC-enhanced Ni-based coatings were prepared in situ on a H13 steel substrate by laser cladding with a fibre laser. The influence law of the central temperature per unit mass of powder, acting on the morphology, microstructure, microhardness and friction wear properties of the coating was investigated. The results show that the metallurgical bonding between the WC--enhanced Ni-based coating and base metal (BM) was good. The dilution rate of the clad layer increases with the increase of. WC, Cr3C2 reinforcing phases, FeNi3 solid solution, FeC carburized body, Fe3W3C interstitial compound are mainly present in the coating at different values of The microstructure gradually changes from dendritic and cellular to irregular aggregation with increasing. The microhardness of the coating increases first and then decreases with the increase of. The microhardness of the coating is the highest when 1=16483 K/g. A value of a=16483 K/g gave the best wear performance. The wear mechanism of the WC-enhanced Ni-based coating is mainly adhesive wear, brittle spalling and abrasive wear. [ABSTRACT FROM AUTHOR]

A Ni60/WC gradient composite coating was prepared on the surface of H13 steel by the laser cladding in situ generation method using a fibre laser. The phase composition, microstructure, microhardness and wear mechanism of the laser clad Ni60/WC gradient composite coating were analysed to reveal that it possessed few pores and cracks, the delamination phenomenon was obvious, the enhancement phase was small and uniformly distributed, and it formed a good metallurgical bond with the H13 steel substrate. In the laser clad Ni60/WC gradient composite coating the branch reinforcing phases are mainly WC, W2C, WSi2 phases, and a small amount of Cr7C3, FexC and other compounds, and the interbranch structures are mainly A-[Fe,Ni] solid solution and Cr7C3, FexC and other compounds. The Ni60+40% (W+C) and Ni60+20% (W+C) layers gradually decrease in number and size from top to bottom, while the shape gradually changes from irregular tetragonal to petal-shaped. The microhardness of the laser clad Ni60/WC gradient composite coating shows a gradient downward trend from top to bottom, and the maximum hardness can reach 1083.7 HV0.5 and the average hardness was 4.18 times that of the H13 steel substrate. The wear amount of the laser clad Ni60/WC gradient composite coating is 20.3% of the H13 steel substrate. The wear mechanism is mainly adhesive wear, brittle spalling and abrasive wear, which can prolong the service life of the mould and reduce the waste of resources. [ABSTRACT FROM AUTHOR]

The objective of this research was to investigate the influence of laser transmission welding (LTW) process parameters such as welding speed, laser power and stand-off distance on weld strength and weld seam width of polylactic acid (PLA) sheets fabricated using fused deposition modelling. Lap welds of PLA were fabricated using a fibre laser as per L9 orthogonal array. Three levels of input process parameters were considered for laser power (16, 18 and 20 W), scanning speed (5, 10 and 15 mm/s) and standoff distance (210, 230, 250 mm). Analysis of variance (ANOVA) and Grey relational analysis (GRA) were carried out on both weld width and weld strength. Maximum tensile strength and minimum weld seam width of 10.51 MPa and 2.76 mm, respectively, were observed in the specimens which were welded using a laser power of 20 W, welding speed of 5 mm/s and stand-off distance of 250 mm. [ABSTRACT FROM AUTHOR]

In our study, we employed a Mo2TiAlC2 thin film as a passive saturable absorber (SA) to create a stable pulsed fibre laser at 1564.52 nm. We synthesized a Mo2TiAlC2-PVA thin film with a 6% modulation depth and a 10 MW/cm2 saturation intensity. This thin film was integrated into the laser cavity between FC/PC fibre connectors, enabling Q-switching over a pump power range of 30 mW to 120 mW. This resulted in an increased repetition rate from 31.1 kHz to 66.83 kHz and a reduced pulse duration from 13.45 µs to 6.35 µs. The pulse train's stability was confirmed by a high signal-to-noise ratio (SNR) of 58 dB. The laser achieved a maximum output power of 6.56 mW and a pulse energy of 98.16 nJ. These results demonstrate Mo2TiAlC2 as a viable Q-switching modulator in the 1.55-µm wavelength range, with promising applications in compact and efficient pulsed fibre lasers. [ABSTRACT FROM AUTHOR]

Silver alloys are often used for electrical switches in railway transportation. However, a well-known issue with these switches is their relatively short application period due to certain disadvantages of silver alloys, mainly their low hardness and low resistance to abrasive wear, in contrast to their excellent electrical conductivity. Therefore, the main goal of this study was to increase or maintain the hardness of the surface layer in order to extend the life of worn parts without compromising their electrical properties. Instead of ceramic particles, as in other studies, metallic powders were used, which could increase the electrical and/or thermal properties of silver alloys. The following work presents the use of laser processing as a relatively new technique for metal and metal alloy surface processing technology. In particular, a process based on the melting of silver (Ag) with metallic powders, such as chromium (Cr) and nickel (Ni) particles, is presented. The aim was for these powders to create intermetallic phases with a silver matrix in the obtained surface layer, significantly improving the mechanical properties based on the formation of the phases coherent or semi-coherent with the silver matrix. Regarding the original practical implications of this work, it was important to investigate the possibility of applying fibre laser for surface property enhancement. The scientific aim was to describe the changes in microstructure and compounds that occurred in the laser-remelted surface silver layer after Ni and Cr particles were fed into the basic silver material. It was concluded that the surface layer obtained after chromium application was without cracks and defects and had a higher hardness than the untreated material. A three-zone structure was also found in the obtained surface layer: (1) the remelted zone, (2) the heat-affected zone, and (3) the matrix material. The remelting zone revealed a higher hardness compared to the untreated material, reaching 92 HV0.3, which is more than twice the initial hardness value.

This paper deals with the laser cleaning of 34CrMo4 steel pipes to be adopted before the electrical upsetting process. The cleaning aims to decrease the pipes' roughness and the coupled electrical resistance with copper inserts to achieve lower wear and obtain an overall better electrical contact between the pipe and the copper inserts. Compared to a traditional process (shot blasting), the results showed that the laser cleaning treatment leads to a lower pipe roughness and a lowered wear of the copper inserts. The first experimental tests were conducted by using a 30-W Q-switched Yb:YAG fibre laser with different cleaning parameters such as scan speed, pulse frequency, and hatch distance to identify a workability range. Successively, a three-level full factorial plan was developed, and results were analysed through the analysis of variance (ANOVA) to understand which parameters were significant during the cleaning process. Also, the cleaned samples were compared to shot-blasted ones to evaluate the percentage improvements in terms of surface roughness, wear resistance, and coupled electrical resistance. In the third phase, a pre-industrialisation analysis was performed by adopting higher laser power sources (50–100 W) to reduce the cleaning time and define a possible industrial setup. It was found that with the laser cleaning treatment the surface quality increases (about 10 times lower Ra and Rz compared to shot blasting), with a decrease of the wear of about 22%. Moreover, the laser cleaning treatment improves the electric contact resistance and reduces the initial variability compared to the as-rolled sample. [ABSTRACT FROM AUTHOR]