Increase Of Scanning Speed Research Articles

Effect of processing parameters on the quality of overhanging round hole structure in AlSi10Mg selective laser melting

To improve the forming quality of overhanging round hole parts without support, the effects of different processing parameters on the forming quality of the structure were investigated by numerical simulation and experiment. The response surface method was used to analyze the collapse of the overhanging surface. A quadratic response model was established, which can be used to predict the optimization of processing parameters. Finally, three groups of parts under different processing parameters were fabricated by SLM, and the forming quality of the parts was analyzed from the macroscopic and microcosmic perspectives. The results showed that the roundness, the collapse of the overhanging surface and the surface roughness increased with the increase of laser power. The result of increasing scanning speed was opposite. With the increase of scanning spacing, the surface roughness decreased continuously, and the roundness and collapse of the overhanging surface increased first and then decreased. When the scanning spacing was 0.15 mm, the roundness and collapse of the overhanging surface reached the minimum. With the increase of the three, the density and hardness increased first and then decreased. The results of response surface analysis were in good agreement with the experimental results.

Effect of welding speed on butt joint quality of laser powder bed fusion AlSi10Mg parts welded using Nd:YAG laser

Abstract The invention of additive manufacturing technology, such as laser powder bed fusion, was initiated by the aerospace industries’ growing need for lightweight alloy components with intricate geometries. However, widespread adoption of lightweight alloy components is limited by size restrictions. Currently, only relatively small and simple-shaped objects can be efficiently produced using lightweight alloys. Thus, this research aims to investigate the effect of welding speed on butt joint quality of laser powder bed fusioned AlSi10Mg parts welded using an Nd:YAG laser. Laser beam welding is a method for welding small parts manufactured by laser powder bed fusion together to build large-scale and complex-shaped objects. Using a 2 kW continuous wave solid-state Nd:YAG laser with three different weld scan speeds (150, 175, and 200 mm min−1), autogenous, single-pass, square butt joints were created from 3 mm thick plates. Crystal orientation mapping and fractography results showed that the laser beam welding scan speed significantly impacts plastic deformation and fracture behavior. A significant amount of grain refinement and an Si-particle morphology change was realized in the weld zone’s microstructure, attributed to the increase in weld scanning speed. The transverse tensile test demonstrates that increasing the weld scan speed from 150 to 200 mm min−1 leads to significant growth in the efficiency of the weld joint, from 70 % to 77 %, arising from grain refinement (13–8 µm). However, a significant decrease in ductility is observed with increasing scan speed. In addition, it was determined that pores have substantial effect on tensile strength and ductility.

Experimental Study on the Influence of Ultraviolet Laser Parameters on the Micro Machining Quality of Silicon Carbide Ceramic

Silicon carbide(SiC) ceramics have great application value in microelectronics and semiconductors due to their small dielectric constant, high thermal conductivity, and small thermal expansion coefficient. However, due to its high hardness and brittleness, defects such as stress concentration, microcracks, and an excessively large heat-affected zone are prone to occur in traditional machining methods. In this paper, the ultra-thin SiC surface was micro-grooved by ultraviolet(UV) laser. The effects and rules of various machining parameters (scanning speed, repetition frequency, pulse width, defocus amount) in UV laser micro-grooves machining on the surface quality, machining depth, and cross-sectional morphology of SiC were studied. The experimental results showed that the surface roughness of SiC micro-grooves decrease with the increase of scanning speed; The relatively small surface roughness (R a 0.72 μm) could be obtained at a scanning speed of 500 mm s−1 and a repetition frequency of 40 kHz; Under low pulse width of 5 ns, high repetition frequency of 50 kHz, and high scanning speed of 500 mm s−1, micro-grooves with a relative error of 2.3% in removal depth could be obtained; The taper of the micro-groove section first decreases and then increases with the defocus from negative to positive, and reached the minimum value of 5° when the defocus positive 0.6 mm.

Quantitative study of geometric characteristics and formation mechanism of porosity defects in selective laser melted Ti6Al4V alloy by micro-computed tomography

The defects formed inside the additive manufactured (AM) part have a detrimental effect on the mechanical performance of the printed component. The effect of defects on the performance of parts varies with their geometry features. The characteristics of porosity defects in 36 bulk Ti6Al4V specimens with different printing parameters were investigated via X-ray computed tomography (XCT). The porosity defects are classified into four types: spherical- shaped, elliptical-shaped, elongated-shaped and irregularly-shaped pores, based on their geometric characteristics. Elongated-shaped defects account for the largest proportion of defects with all printing parameters, and the proportion of irregularly-shaped defects enhances with the increase of scanning speed. The characteristics of gradual accumulation of defects in single-track and multi-track samples were also analyzed. Porosity may gradually accumulate with the overlay of layers, while the appropriate overlapping rate may melt the pores between the tracks. The formation of defects is greatly influenced by surface roughness and pool wetting.

Study on the process optimization and wear resistance of electron beam cladding AlCoCrFeNi coating on 253MA austenitic stainless steel surface

This study employs a continuous scanning electron beam to deposit AlCoCrFeNi composite cladding on the surface of 253MA austenitic stainless steel to enhance its surface properties. The characteristics were examined through a scanning electron microscope (SEM), backscattered electron diffraction (EBSD), and white light interferometric three-dimensional surface profile instrument. This study investigated the effect of electron beam process parameters on the surface organization and mechanical properties of 253MA steel. The sample surface was divided into four zones: overlay, bonding, thermal influence, and substrate, according to the results. Coarse columnar and island-shaped crystals composed the overlay zone, while equiaxed austenite grains primarily constituted the substrate. With the increase of the beam current, the microstructure's grain size decreased, the substructures increased, and the BCC phase transformed into the FCC phase. The grain size slightly decreased, substructures changed marginally, and the BCC phase increased as the scanning speed increased. Additionally, the microhardness and mechanical properties of the overlay layer increased significantly, and wear volume and wear rate decreased progressively with the increase in beam current and scanning speed. At a beam current of 18 mA and a scanning speed of 200 mm/min, the surface hardness of 253MA steel reached the maximum value of 520 HV. When the beam current was 24 mA, and the scanning speed was 200 mm/min, the wear volume and wear rate of the overlay sample were minimal, accounting for 37.4% of the original sample's, and its wear resistance was 2.67 times more than that of the substrate.

Influence of scanning speed on the microstructure, nanoindentation characteristics and tribological behavior of novel maraging steel coatings by laser cladding

This paper utilized a novel high-Mo maraging steel powder to prepare maraging steel coatings through laser cladding. The study investigated how scanning speed affects the microstructure, phase formation, nanoindentation properties, and wear properties of the resulting laser-clad maraging steel coatings. The experimental results reveal that the maraging steel coating consists of martensite and austenite phases. Moreover, diffraction peaks of Fe2Mo phase were observed at low scanning speeds. As the scanning speed increases, there is a gradual reduction in the austenite content, accompanied by a decrease in the Fe2Mo phase content. Moreover, both martensite and austenite exhibit an increase in lattice distortion. EBSD analysis demonstrates a reduce in grain size as the scanning speed increases, accompanied by the emergence of LAGBs and an increase in dislocation density, as indicated by the rising KAM value. TEM analysis confirms the presence of a Mo-rich precipitated phase, characterized by a dense hexagonal structure consisting of the Fe2Mo intermetallic compound. The Fe2Mo phase displays high hardness, thereby significantly enhancing the second precipitation strengthening effect of the coating. The nanoindentation characteristics of the S2 coating are exceptional, displaying remarkable values for nanohardness, HU, H/E ratio, and H3/E2 ratio. Specifically, the S2 coating exhibits a nanohardness of 4.843 ± 0.104 GPa, accompanied by an HU value of 0.2073 GPa. Additionally, the H/E ratio and H3/E2 ratio are reported as 0.0214 and 0.002218, respectively. Demonstrates excellent mechanical properties of S2 coating. Furthermore, the S2 coating demonstrates outstanding performance in terms of wear resistance and deformation resistance, exhibiting the lowest friction coefficient and specific wear rate, measuring at 0.438 and 1.381 × 10−5 mm3/N•m, respectively. The observed wear mechanisms in the S2 coating include adhesive wear, abrasive wear and oxidative wear. Notably, lower scanning speeds promote the precipitation of Fe2Mo particles, which play a supportive role in the wear process by weakening the tendency of oxidative wear. Overall, the remarkable properties exhibited by the S2 coating, such as nanohardness, wear resistance, and deformation resistance, position it as a promising candidate for various technological applications.

Microstructure and tensile behavior of CO2 laser beam welded AISI 409 ferritic stainless steel tubes

Laser beam welding (LBW) is a suitable process to join ferritic stainless steels (FSS). LBW process helps to suppress grain growth and intermetallic phases. CO2-based laser source was used to join AISI 409 FSS tubes having a thickness of 4 mm. The laser scanning speed, which determines the production rate, was varied from 1.3 m/min to 3.3 m/min. There were no defects at the joint region except an undercut at the highest scanning speed. The micrographs showed no coarsening of grains at HAZ. The fusion zone showed a dendritic structure composed of columnar grains and axial grains. The increase in scanning speed refined the dendritic structure. The fusion zone experienced phase transformation from δ ferrite to martensite. TEM micrographs revealed the formation of substructures and dislocation fields. The microstructural changes caused the strengthening of the fusion zone. The joint strength in most of the weldment reached the strength of the base metal. All the joints failed in a ductile manner and the elongation was more than 10%.

Molten pool image processing and quality monitoring of laser cladding process based on coaxial vision

Aiming at the problems of the traditional detection method of cladding quality in laser cladding process, which relies on experience, has low accuracy and long recognition time, a method based on the image area of molten pool is proposed to detect cladding quality. Firstly, the median filter algorithm with dynamic adjustment of filter window is used to reduce noise and the iterative threshold segmentation algorithm is used to separate the molten pool from the boundary, then the edge of the molten pool is extracted by Canny algorithm which can adaptively change the high and low thresholds and finally the area value of the molten pool is obtained according to the correspondence between the pixel value and the actual value. The relationship between three key factors (nozzle angle, scanning speed and laser power) and molten pool area is analyzed to achieve favorable cladding quality. The results show that the influence of nozzle angle on the molten pool area is anisotropic. And the molten pool area decreases monotonically with the increase of scanning speed, while the higher velocity will destroy the formation of the molten pool. In addition, with the increase of laser power, the expansion of molten pool area is intensified. At the same time, the analysis of the change of molten pool area over time can quickly and accurately detect the three defects (protrusion, depression, and slag inclusion) in the process of cladding.

Study on the Rate of the Removal of Nano-Crystalline Diamond—Coated Materials by Femtosecond Laser Etching

The rate of the removal of materials coated with nano−crystalline diamonds by femtosecond laser etching was examined by adjusting the repetition rate of the femtosecond laser, the energy−flux density of the concentrated spot, and the scanning speed. The observational results of the white-light interferometer and the numerical fitting approach were used to develop the removal rate function model of the nano-crystalline diamond-covered material etched by the femtosecond laser. The findings demonstrated that the rate of material removal was not greatly affected by the repetition frequency and that the amount of laser energy accumulated over time on the coated surface is steady. The processing outcomes under different laser scanning speeds are different, and the material removal rate tends to increase and then decrease with an increase in scanning speed. The greater the energy−flux density of the focused spot, the greater the etching intensity, and the greater the material removal rate. With an increase in scanning speed, the rate at which the material is removed often rises initially before falling.

Role of scanning speed on the microstructure and mechanical properties of additively manufactured Al2O3‒ZrO2

AbstractMelt‐grown Al2O3–ZrO2 eutectic (AZ eutectic) ceramics have attracted extensive attention for harsh environment applications. In this work, AZ eutectic ceramic is additively manufactured via one‐step laser powder bed fusion (LPBF). The role of scanning speed on phase formation, crystallographic characteristics, microstructure evolution, and mechanical properties were systematically investigated. The as‐fabricated specimens are mainly composed of α‐Al2O3 and t‐ZrO2. Lower scanning speeds induced the formation of cellular structures consisting of randomly oriented ZrO2. In contrast, nanometer eutectic lamellar structure with well‐defined multiple crystallographic orientation relationships, for example, {100} Al2O3 || {100} ZrO2 and {0001} Al2O3 || {001} ZrO2, occurred at higher scanning speeds. Both the cell size and lamellar spacing decreased with increasing scanning speed. With the microstructure refinement, the crack propagation mode changes from intergranular to transgranular fracture, leading to progressively enhanced fracture toughness with a maximum value of 7.76 MPa·m1/2. The present work could shed light on tailoring the microstructure of LPBF AZ eutectic ceramic via varying processing parameters.

Effects of scanning speed and scanning times on surface quality of line spot laser polishing of nickel-based superalloys

Nickel-based superalloy (DZ411) is widely used in aerospace and other fields due to its excellent physical properties, and the improvement of surface roughness is necessary in practical applications. In this paper, a machining platform that uses a beam shaper to modulate a circular spot into a line spot is used to perform laser polishing on the initial material surface by changing the scanning speed and scanning times, respectively. The results show that the line spot laser polishing can make the surface shallow melting to achieve the purpose of smoothing the surface. By changing the number of scanning times, the roughness of the polished surface Ra can be reduced from 0.702 μm to 0.354 μm. The percentage of improvement in surface roughness is 49.5%. The formation of oxides on the surface results in a slight increase in microhardness. In the test of changing the scanning speed, the roughness of polished surface roughness Ra can be reduced to 0.390 μm, Ra first decreases and then increases as the scanning speed increases. The polishing surface processing speed can reach 26.209 cm2/min, which has the potential to achieve efficient laser polishing. This research work can provide guidance for the optimization of line spot laser polishing parameters based on beam modulation and provide process data support for the efficient processing of nickel-based superalloys with line spot.

Simulation of microstructure evolution process in the melt pool formed by laser cladding with a multi-scale model

The microstructure directly determines the alloys’ mechanical performance, therefore understanding the microstructure evolution process is essential to controlling the cladding layer’s mechanical performance. A multiscale model in three dimensions is developed to evaluate the complicated microstructure evolution in the melt pool formed during the laser cladding process. The model consists of two parts: the FVM to calculate the evolution of the melt pool at the macroscopic scale, and the simulation of the solidification of grains at the microscopic scale by the CA. The high consistency with the experimental results proves the accuracy of the multiscale model in three dimensions. Using the developed model, the solid-liquid phase transformation process of the whole melt pool is studied and the impact of the variations of scanning speed on the microstructure is analyzed. The grain size decreases and the “laser-grain angle” increases with an increase in scanning speed. This study explains the evolution of the microstructure, which helps to customize the cladding layer’s microstructure.

Microstructure evolution and tensile property of high entropy alloy particle reinforced 316 L stainless steel matrix composites fabricated by laser powder bed fusion

316 L stainless steel is prone to failure under high-strength conditions due to low strength and poor wear resistance, which limits its further application severely. In this study, 2 wt% FeCoNiAlTi high entropy alloy (HEA) powders and 316 L stainless steel powders were mixed to fabricate HEA reinforced 316 L stainless steel matrix composites (MMCs) via laser powder bed fusion (LPBF). The influence of scanning speed on microstructure evolution, the mechanical properties and the strengthening mechanisms have been investigated systematically. The LPBF-fabricated HEA/316 L MMCs consists of both γ-Fe and α-Fe phases. For HEA/316 L MMCs, the grains are refined with the increase of scanning speed and the minimum size is around 0.64 µm. The precipitation of nanoparticles is observed, and the nanoparticles form a strong interfacial bounding with matrix, which indicates the good metallurgical bonding between HEA and 316 L stainless steel. The tensile strength of the LPBF-fabricated composites increases from 1164 MPa to 1276 MPa with increased scanning speed, which is approximately twice as high as the strength of LPBF processed 316 L stainless steel matrix. The contribution of each strengthening mechanism is calculated, and the contribution of particle strengthening is the largest (from 241 MPa to 300 MPa, changing with scanning speed). This work demonstrates the feasibility of using HEA as potential reinforcement in metallic systems and can further enlarge the application field of metallic materials.

Tailoring the microstructural and mechanical properties of 316L stainless steel manufactured by laser powder bed fusion

The grains, cellular structures, dislocation densities, and oxides in L-PBF 316LSS were systematically characterized. The microstructure evolution and mechanical properties were closely associated with the scanning speed. The sizes of grains and oxides in L-PBF 316LSS significantly decreased with increasing scanning speed, while the dislocation density remained relatively stable for speeds from 500 to 900 mm s−1 and significantly increased when the scanning speed exceeded 900 mm s−1. The tensile samples exhibited obvious anisotropic mechanical properties, and the TD samples showed higher strength, attributed to the strong <110> crystallographic orientation, while <111>-oriented grains facilitated activation and generation of deformation twins. Importantly, the cellular substructures were traversed by deformation twins, leading to their subdivision and dissociation. The discontinuous dislocation tangles interacted with deformation twins and provided a continuous and stable work hardening capability, resulting in superior ductility of BD samples. Reasonable agreement between the yield strength experimental results and theoretical calculations was achieved, suggesting that the superior strength and ductility for L-PBF 316LSS can be attributed to the grain boundary strengthening, oxide dispersion strengthening, dislocation strengthening and work hardening behavior. Collectively, this study revealed the strengthening mechanism of L-PBF 316 L stainless steel, which can provide theoretical guidance in the development of new alloy materials.

Tailoring the crystallographic texture of biomedical metastable β-type Ti-alloy produced via laser powder bed fusion using temperature-field simulations

Recently, the use of laser powder bed fusion (LPBF) to create crystallographic textures, such as single-crystal-like and polycrystalline textures, has attracted attention. However, the relationship between the LPBF conditions and the resulting texture is unclear. This study investigates the effects of the LPBF conditions (laser power and scanning speed) on the texture by estimating the solidification behavior using temperature-field simulations. Herein, we show for the first time that laser power and scanning speed negatively and positively affect the solidification rate R, respectively, and do not affect the thermal gradient G significantly. Thus, when the laser power decreases and scanning speed increases, the G/R ratio decreases and polycrystal formation is enhanced. This is consistent with practical observations.

Features of Increasing the Wear Resistance of Machine Parts by Treatment with a Concentrated Heat Flow

The article discusses the possibility of using surface treatment of parts with a concentrated heat flow to increase the wear resistance of parts. This method provides conditions for the rapid crystallization of the metal structure after zonal surface melting of the sample surface with electric arc plasma. It has been found that the wear resistance of steel increases significantly with increasing scanning speed and decreasing current strength. The near-surface layers on the cross-sectional grinds of the melting areas were studied in comparison with the initial (without melting) state on the basis of diagrams of the method of continuous indenter immersion. The values of a number of micromechanical parameters characterizing the resistance to microplastic deformation and elastic-viscous properties of steel after strengthening heat treatment were obtained. It should be noted that with a fourfold increase in hardness, the wear resistance of the steel increased almost 10 times. This indicates that the wear resistance of metals under friction is determined not only by macroscopic strength and hardness, but also by the ability to relax local peak stresses under dynamic contact interaction

Effects of process parameters on surface quality and mechanical performance of 316L stainless steel produced by selective laser melting

Selective laser melting (SLM) is a commonly used additive manufacturing technique for 316L stainless steel. In this study, the process parameters of 316L stainless steels fabricated by SLM method on surface quality and mechanical performance were investigated. The SLM method parameters and energy density significantly affect the mechanical performance and surface quality. Laser power and real spot size were kept constant at 370 W and 0.12 mm, respectively. The effect of different scanning speeds (900–1100–1300 mm/s), layer thicknesses (0.04–0.05–0.06 mm) and scanning gaps (0.09–0.1–0.11 mm) were analyzed. The increase in scanning speed affected the surface quality negatively. The highest mechanical performance was obtained at the laser power 370 W, scanning speed 1100 mm/s, layer thickness 0.04 mm, scanning gap (space) 0.1 mm, real spot 0.12 mm, overlap ratio 0.833 % and energy density 84.09 J/mm3. As a result of the study, it was observed that the mechanical performances were improved by increasing the input energy density.

Increasing the scan speed in high resolution, low energy electron diffraction measurements by presetting the gate time.

We report on a speed-up data acquisition routine for recording intensities in reciprocal space (k-space) with increased scan speed by a single point detector. It is designed for recording low energy electron diffraction (LEED) data with high resolution by a spot profile analysis LEED instrument. It counteracts the problem of long acquisition times that are encountered when larger areas in the reciprocal space are scanned. It exploits the fact that in typical LEED images of ordered surfaces, more than 90% of the data points in k-space belong to the low-intense background, which is often not of interest. Only about 10% of the data points are related to the relevant diffraction features, namely, the LEED spots. Often it is not necessary to measure the background with the same statistical significance as measuring those points that contain information. The data points belonging to the LEED spots can be discriminated from those of the background by their higher intensities. An acquisition routine that sets an increased gate time for the counting in response to higher intensities thus safeguards good statistics for data points of the LEED spots and saves measurement time when recording data points of the background with small gate times. For typical LEED images, a reduction of the total acquisition time by a factor of about 10 is obtained. We give examples of one- and two-dimensional scans from current experiments, recorded with and without the speed-up routine. We further discuss how the routine supports the measurement of energy dependent reciprocal space maps.

Solidification characteristics and microstructure of TaNbZrTi refractory high entropy coating by extreme high-speed laser cladding

Extreme high-speed laser cladding (EHLC) has shown potential in producing refractory high entropy alloy (RHEA) coatings with excellent forming quality. However, there is a lack of theoretical guidance for the EHLC process, and the traditional heat source model is unsuitable. In this study, the laser-molten metal composite heat source model was improved based on the characteristics of EHLC, and a temperature field model suitable for EHLC tubular matrix surface was established and verified by infrared thermal imaging. The solidification characteristics and microstructure of TaNbZrTi RHEA coating prepared by laser cladding (LC), high-speed laser cladding (HLC), and EHLC were compared through temperature field simulation and experimental characterization. The results indicate that the cooling rate of molten pool increases significantly with the increase of scanning speed. EHLC coating has higher cladding efficiency, lower heat accumulation and dilution rate, and denser grain structure compared to LC and HLC coatings. TaNbZrTi coating exhibits a BCC1 + BCC2 phase structure, and the hardness of LC, HLC, and EHLC coating is 577.5, 487.8, and 545.2 HV0.3, respectively. This study provides a simulation model and process guidance for the preparation of TaNbZrTi RHEA coatings.

Machinability of AA 2024 aluminum alloy by fiber laser engraving process

AbstractThe main objective of the present study is to investigate the machinability of AA 2024‐T351 aluminum alloy by laser beam‐assisted engraving process. The surface in a defined area was machined with the engraving process parameters of scan speed, frequency, and pulse width. While surface roughness measurements were performed to characterize the texture of the processed surface with laser engraving parameters, machining depth measurements were carried out to determine the material removal capacity. In addition, a mathematical relation was built for engraving depth and surface roughness using the response surface methodology. An increase in scan speed and pulse width led to a decrease in engraving depth and surface roughness. Unlike the scan speed and pulse width, any increase in frequency led to increased surface roughness and decreased engraving depth. After processing with lower pulse width and scan speed, a chaotic topography was formed on the surface. The effects of process parameters on engraving depth and surface roughness were analyzed statistically using factorial analysis. Except for the frequency, all parameters for surface roughness were statistically significant, whereas all parameters for engraving depth were statistically significant.