Influence Of Scanning Speed Research Articles

Effect of residual stress on mechanical properties of Triply periodic minimal surface lattice structures in Additive manufacturing

Due to its special porous structure with smooth continuous surface and high specific surface area, the triply periodic minimal surface (TPMS) lattice structure exhibits excellent properties such as strong bearing capacity, high energy absorption rate and good fatigue performance. The residual stresses generated during the additive manufacturing (AM) process can have a significant impact on the mechanical properties of the TPMS structure. In this paper, the AM process of four typical TPMS structures are investigated by the thermal–mechanical coupling model. The mechanism of residual stress generation is analyzed, and an optimized preparation process scheme is proposed to reduce the residual stress. Furthermore, the effects of residual stresses on the mechanical properties of TPMS structures are investigated for different types, volume fractions and compression directions. Results show that the influences of scanning speed and hatch spacing on the residual stress are not significant with constant laser power, but the deposition thickness should be adjusted according to the characteristics of the structure. The residual stress will reduce the elastic modulus and yield strength, while no obvious effect on the plastic behavior is observed. Importantly, the residual stress has the greatest influence on the mechanical properties of I-WP-type among the four investigated types, which becomes more pronounced with the increase of volume fraction. Moreover, the influence of residual stress on the mechanical properties of TPMS structures depends on the compression direction. Our results give a comprehensive understanding of the residual stress distribution and impact on the mechanical properties of TPMS structures, providing guidance to the rational design and optimization of TPMS structures in engineering applications.

Numerical simulation of single-pass selective laser melting of Mg-Y-Sm-Zn-Zr alloy

A three-dimensional finite volume method (FVM) thermal-fluid coupling model was developed to simulate the temperature field distribution and dimensions of the melt pool in selective laser melting (SLM) of Mg-Y-Sm-Zn-Zr alloy powder. This model aims to accurately determine the temperature field and surface morphology of the melt pool by considering the laser's impact on powder particles, free surface dynamics, convection, and multiphase heat transfer. The study explores how laser power and scanning speed influence temperature distribution, melt pool size, and flow dynamics. The findings show that increasing laser power or reducing scanning speed consistently affects the melt pool size, peak temperature, and cooling rate. During the evaporation of the alloy in the melt pool, fluid flow is primarily governed by recoil pressure and Marangoni convection. Notably, increasing the laser power from 40 W to 100 W and the scanning speed at 0.3 m/s enhances the depth of the melt pool indentation from 13.86 µm to 23.35 µm. Furthermore, the indentation depth correlates positively with the laser line energy density.

Influence of scanning speed on titanium alloy processed with TC4+Ni60/hBN composite powder by laser metal deposition coating technology

PurposeRegarding the broadening of the titanium alloy application field, the surface treatment coating of TC4 alloy has become an essential global research topic. This study aims to illustrate the titanium-based composite coating is created by laser cladding TC4+Ni60/hBN composite powder onto the surface of the TC4 alloy.Design/methodology/approachDifferent laser scanning speeds were initially selected to prepare TC4+Ni60/hBN titanium-based composite coating on the surface of TC4 alloy using RFL-C1000 Raycus fiber laser. Second, the cladding layers with different laser scanning speeds are composed of Ti2Ni, TiN0.3, TiC, TiB, α-Ti and other phases. Finally, precision balances, friction and wear testing machines were used to analyze and test the structure, phase, hardness, wear amount and friction coefficient of the composite coating and to study the effect of laser scanning speed on the microstructure and properties of the titanium-based composite coating.FindingsIt is evident that at the low laser scanning speed, the reinforcing phase agglomeration area is distributed in the substrate as a network. Increasing the laser scanning speed can reduce the cladding layer's friction coefficient and improve the cladding layer's hardness and wear resistance. But too high a laser scanning speed will cause defects such as pores and cracks in the cladding layer and also affect the cladding layer. The bonding performance of the layer and the substrate is optimal in this research at a laser scanning speed of 10 mm/s.Originality/valueThis research has practical value in improving the quality of surface treatment coating in modern aerospace and automotive companies.

An experimental and numerical study on the evolution of pores and its effect on the tensile properties of LPBF Invar36 with different energy density

Laser powder bed fusion (LPBF) Invar 36 alloy has attracted plenty of attention in cryogenic components or precision instruments due to its low coefficient of thermal expansion in a wide range of temperature. However, the LPBF Invar 36 has a significant anisotropic mechanical property due to the unique columnar grain morphology and pore feature. In this study, the influence of scanning speed on the anisotropic tensile properties were investigated, and the melt pool dynamics were analyzed by the numerical simulation. In this respect, tensile tests of specimens parallel and perpendicular to the building direction with a scanning speed from 200 to 1400 mm/s of LPBF Invar 36 alloy were conducted, and the microstructural influential factors on the anisotropic tensile properties were analyzed. Results show that as the volumetric energy density (VED) increases, the inhomogeneity of grain morphology decreases, while the pore feature changes from the lack-of-fusion (LOF) pore perpendicular to the building direction to the bubble-shaped spherical pore, which is resulted from the collapse of the key-holes. In this case, the grain orientation and size, as well as the dislocation density in the vicinity of pores are influenced by the pore morphology due to different thermal history. On the whole, the combined morphology of dislocation and stress concentration affected by the pore morphology are the main reason of the increased level of anisotropy in tensile properties.

Influence of scanning speed on microstructures and mechanical properties of SLM produced Hastelloy X: as-built and solution-treated

Hastelloy X (HX) alloys with ideal strength and ductility match can be obtained by selective laser melting (SLM) and a proper follow-up heat treatment. This work studies the influence of scanning speed on grain size, grain boundary distribution, recrystallization and mechanical properties of as-built HX. These influences are reevaluated after a solution treatment at 1175 °C for 4h. The results reveal that the average grain size decreases, while the aspect ratio, texture intensity and the proportion of high-angle grain boundaries (HAGBs) increases with the increase of scanning speed. A small amount of recrystallization has occurred in the as-built alloys due to the cyclic thermal effect of SLM scanning. The finer grains and larger aspect ratio imply the higher energy storage during SLM, which will increase the recrystallizing nucleation rate. Solution treatment eliminates the fiber texture of 〈100〉//BD, significantly increases the HAGBs fraction and recrystallization fraction, reduces the grain aspect ratio, and coarsens the grains. With the increase of scanning speed, the strength of the Hastelloy X increases and the elongation decreases. The decrease of grain size is the main reason for the increase of yield strength.

Experimental and numerical investigation of the effect of process parameters on crack formation and residual stresses in the laser coating process of stellite 6 alloy on X19CrMoNbVN11-1 steel substrate

In the present research, thermal–mechanical simulation of laser cladding of Stellite 6 powder on X19CrMoNbVN11-1 steel substrate was carried out to study the influence of scanning speed and laser power on the remaining stresses/strains and thus the formation of cracks in the cladding layer. In order to demonstrate the accuracy of the simulation results in prediction of the crack formation, the laser cladding process was also implemented experimentally. The results have shown that the highest temperature of the molten pool (1753 °C) was obtained at a laser power of 250 W, a powder injection rate of 0.3 g/s and a scanning speed of 3 mm/s. With the increase in scanning speed, the geometric shape of the cladding layer has changed from a semicircle to an oval shape. Moreover, at low scanning speed, the maximum strain is produced in the substrate and at high scanning speed, the maximum strain is created at the top of the coating layer. The lowest value of residual stress and strain was obtained at a scanning speed of 3 mm/s, while at a scanning speed of 5 mm/s the highest value of residual stress and strain was obtained. Furthermore, when the wetting angle is greater than 44°, the stress concentration is transferred from the top of the cladding layer to the substrate and the possibility of crack formation decreases.

Influence of scanning speed on microstructure and corrosion resistance of Fe-based amorphous coatings by high-speed laser cladding

Fe-based amorphous coatings were prepared on the surface of the AISI 1020 steel pipe by high-speed laser cladding technique. This study is aimed to investigate the influence of scanning speed on the microstructure, hardness, amorphous content and corrosion resistance offered by the Fe-based amorphous coatings. The results showed that, the coating obtained at 50 mm/s exhibited a distinct three-layer hardness distribution, with the second layer displaying the highest hardness. This phenomenon was primarily ascribed to amorphous strengthening, fine-grain strengthening, and martensitic strengthening. The bottom region of the coatings contains budding crystals, with prominent aggregation of elemental Fe. Away from the budding regions, a transition from columnar to dendritic crystals was observed. The amorphous content of the coatings exhibited an initial rise followed by a decline with increasing scanning speed. Among these, the amorphous phase content of 130 mm/s coating was up to 95 %. Differential Scanning Calorimetry (DSC) test results confirmed the presence of amorphous phases in the bottom and middle regions of the 50 mm/s coating. Electrochemical experiments underscored the exceptional corrosion resistance of the 130 mm/s coating, evidenced by its maximum corrosion potential (−0.471 V), minimal corrosion current density (2.7 × 10−6 A/cm2), and highest polarization resistance value (22,149 Ω·cm2). This superior performance was attributed to the presence of the amorphous phase and the Cr oxide layer formed on the surface, providing robust protection to the substrate.

The Influence of Scanning Speed on the Removal of Polyethylene Films with Different Colors by 1 μm Continuous Laser was Studied

The Influence of Scanning Speed on the Removal of Polyethylene Films with Different Colors by 1 μm Continuous Laser was Studied

Effect of scan speed on corrosion and tribocorrosion properties of cobalt-chromium alloy in situ produced by selective laser melting

Purpose This paper aims to investigate the influence of scan speed on the corrosion and tribocorrosion features of the CoCrMoW samples fabricated via the selective laser melting (SLM) process. Design/methodology/approach CoCrMoW samples were produced by SLM at different scan speeds. Produced samples were made via structural surveys (X-ray diffraction examinations and scanning electron microscopic analyses), hardness measurements and electrochemical and tribocorrosion experiments. Findings Outcomes displayed that the corrosion and tribocorrosion properties of CoCrMoW alloy were significantly influenced by scanning speeds. Also, these properties of the alloy increased with increasing scanning speeds. CoCrMoW samples produced at a laser scan speed of 1,000 mm/s showed the best resistance to corrosion and tribocorrosion. This could be related to the high hardness and low grain structure of the fabricated samples. Originality/value This paper may be a practical reference and offers insight into the effect of scanning speeds on the increase of hardness, tribological and corrosion performance of CoCrMoW alloys. This study can help in the further advancement of cobalt-chromium alloy in situ produced by SLM for both electrochemical and tribocorrosion behavior for biomedical applications.

Laser powder bed fusion of oxide dispersion strengthened FeCrAl alloy: Processing and microstructural evolution

Optimizing and regulating the process parameters to form a uniform distribution of nanosized dispersoids remains a major challenge in additive manufacturing oxide dispersion strengthened (ODS) alloys. This study introduces the influence of scanning speed and laser power on the microstructure evolution of laser powder bed fusion (LPBF) ODS FeCrAl alloy. Low laser power and high scanning speed reduce the size of oxide particles and increase their number density. The energy density threshold is 83 J/m3, below which the powder fails to achieve complete melting, leading to the formation of defects during solidification. High density and large number of oxide particles were obtained for the printed samples under the parameters of 140 W laser power and 600 mm/s scanning speed. The average size and number density of oxide particles were ∼ 21.61 nm and ∼ 1.8 × 1020/m3, respectively. High scanning speed have a rapid cooling rate which affects the dislocation density and the average width of the columnar grains. Low laser power significantly weakens the 〈100〉 fiber texture, which is related to the degree of recrystallization in the remelted region. The core-shell oxides consisting of Y-Al-O and Y-Ti-O were distributed in the samples deposited at low and high laser powers, respectively. The formation of core-shell oxide particles in LPBF ODS FeCrAl alloys involves solid-state amorphization and recrystallization. This study can be a guideline to achieve materials with specific microstructure for ODS alloys.

Effect of scanning speeds on mechanical properties of CoCrNi medium entropy alloy prepared by laser additive manufacturing

Medium entropy alloy (MEA) is a hot spot in the field of material research in recent years. At present, the most widely used processing method of MEAs is “casting-rolling-heat treatment”, and the preparation of CoCrNi MEA by laser additive manufacturing (LAM) is still in primary stage. In this study, CoCrNi MEAs were fabricated with different scanning speeds by laser additive manufacturing, and the influence of scanning speed on its mechanical properties was investigated. The results show that higher scanning speed can significantly improve the mechanical properties of CoCrNi MEA. Compared with the low-speed laser additive manufacturing (LSLAM) MEA, the tensile strength of high-speed laser additive manufacturing (HSLAM) MEA is increased by 5.6 % and the fracture strain is increased by 60 %, which is mainly due to the entanglement of 1/6<112> and 1/2<110> dislocations and the defect structure at the grain boundary. LAM is a promising technology that can promote the development and application of MEAs in industry.

Deformation prediction and shape compensation model of circular channels using laser powder bed fusion

Laser powder bed fusion (L-PBF) technology offers significant advantages, such as lightweight and miniaturized product fabrication and short manufacturing cycles. Circular channels are widely utilized in hydraulic manifold blocks due to their favorable hydrodynamic properties. However, when manufactured using L-PBF, circular channels often exhibit shape deviations caused by residual stresses. In this study, Ti6Al4V (TC4) circular channels with various processing parameters were produced through L-PBF. The influence of scanning speed and laser power on the actual channel profile was investigated. A novel deformation prediction model for circular channels was established based on the Euler–Bernoulli theory. This model accurately predicts deformations resulting from residual stresses during horizontal manufacturing of circular channels using L-PBF, considering the interaction between forces and deformations across different manufactured layers. Furthermore, the model can be employed for channel shape compensation design. The results indicated excellent agreement between the proposed deformation prediction model and the profile of the experimentally manufactured samples. Using the channel shape compensation model for circular channels substantially can reduce the root mean square (RMS) deviation, thereby improving dimensional accuracy.

Effect of scanning speed on fatigue behavior of 316L stainless steel fabricated by laser powder bed fusion

The effect of the scanning speed on the fatigue behavior of Laser Powder Bed Fusion (LPBF)-fabricated 316L steel is investigated in this paper. To this end, fatigue limits of specimen manufactured by different scanning speeds are determined by the self-heating approach. EBSD experiments and relative density measurements are carried out to characterize the microstructure and porosity. To analyse the influence of scanning speed on the microstructure (grain morphology, texture, dislocation density and stored energy) and fatigue property, a dislocation-density, crystal plasticity and stored energy-based fatigue model is developed. The inverse optimization method is combined with EBSD experiments and uniaxial tension experiments to identify the model parameters. The experimental results show a critical scanning speed, below which the fatigue limit stays almost unchanged and decreases drastically while the scanning speed is increased beyond. Furthermore, the simulation results show that the predicted fatigue limits correspond well to the experimental fatigue ones. From experimental and numerical results, it is deduced that the critical stored energy density and maximum temperature variation are functions of the porosity and can be used to differentiate the types of fatigue: microstructure-dominated or defect-dominated. This article provides new insights which can be further used in the optimization of fatigue behavior of LPBF 316L steel with respect to the scanning speed.

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 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.

Effect of Scan Speed on Microstructure and Tensile Properties of Ti–48Al–2Cr–2Nb Alloys Fabricated via Additive Manufacturing

The morphology of microstructure and tensile properties of Ti–48Al–2Cr–2Nb (at%) alloy rods fabricated by the electron beam powder bed fusion (EB-PBF) process were investigated with a particular focus on the influence of scan speed of the electron beam. Homogeneous near lamellar structure composed of the α2 and γ phases can be obtained in the rod fabricated under the slowest scan speed. The fine lamellar spacing which contributes to the high strength of the alloy is derived from the fast-cooling rate of EB-PBF. On the contrary, a layered microstructure comprising a duplex-like region and an equiaxed γ grain layer (γ band) perpendicular to the building direction is obtained when increasing scan speeds. We observed for the first time that an increase in the scan speed results in a narrow width of the γ band. We also found that these microstructural changes have a significant influence on the mechanical properties of the rods. The near lamellar structure exhibits higher strength compared to the layered microstructure. Whereas, the rods with the layered microstructure show large ductility at room temperature. The elongation of each rod strongly depends on the width of the γ band owing to the preferential deformation of the γ band.

Effects of Power and Laser Speed on the Mechanical Properties of AlSi7Mg0.6 Manufactured by Laser Powder Bed Fusion

The AlSi7Mg0.6 alloy, with its good tolerance against strain, is used in laser powder bed fusion (LPBF) to produce parts with complex geometries for aerospace engineering. Production of parts with good mechanical strength requires, however, the optimization of laser parameters. This study thus evaluated the influence of scanning speed, laser power, and strategy on several mechanical properties (tensile/resilience/hardness) to identify an optimal processing region. Results have shown the profound influence of laser power and scanning speed on mechanical properties, with a limited influence from the laser strategy. Tensile strength values ranging from 122 to 394 MPa were obtained, while Young's Modulus varied from 17 to 29 GPa, and the elongation at break ranged from 2.1 to 9.8%. Surface plots of each property against laser power and speed revealed a region of higher mechanical properties. This region is found when using 50 µm thick layers for energy densities between 25 and 35 J/mm3. Operating at higher values of energy density yielded sub-optimal properties, while a lower energy density resulted in poor performances. Results have shown that any optimization strategy must not only account for the volumic energy density value, but also for laser power itself when thick layers are used for fabrication. This was shown through parts exhibiting reduced mechanical performances that were produced within the optimal energy density range, but at low laser power. By combining mid-speed and power within the optimal region, parts with good microstructure and limited defects such as balling, keyhole pores, and hot cracking will be produced. Heat-treating AlSi7Mg0.6 parts to T6 temper negatively affected mechanical performances. Adapted tempering conditions are thus required if improvements are sought through tempering.

Influence of Scanning Speed on the Microstructure and Wear Resistance of Laser Alloying Coatings on Ti-6Al-4V Substrate.

Laser alloying has attracted significant attentions due to the advantages of high processing precision, good controllability and low heat effects on the substrate. However, the complexity of laser alloying requires further attentions on its processing parameters. This study aims at improving the wear resistance of the Ti-6Al-4V substrate by means of laser surface alloying with Ni-coated graphite (G@Ni). The effect of laser scanning speed is explored. The result suggests that the coating has a high surface quality and excellent metallurgical bonding with the substrate. NiTi and NiTi2 have a eutectic microstructure as well as in the TiC ceramic-reinforced phase as dendrites distribute in the γ-Ni matrix of the coatings. At higher scanning speeds, the lower energy density and shorter existence time of the molten pool refines the microstructure of the coating, improving its microhardness. At the scanning speed of 15 mm/s, the coating has the lowest wear weight loss due to its high microhardness and dense structure. This paper explores the influence of scanning speed on the microstructure and properties of the coatings, expanding the application of laser alloying on the surface modification of Ti-6Al-4V alloys.

Effect of scanning speed, scanning pattern, and tip size on the accuracy of intraoral digital scans

Statement of problemCurrently available intraoral scanning technology makes intraoral scanning quicker and allows the use of smaller scanner tips. However, studies on the influence of scanning speed, tip size, and scanning patterns on scanning accuracy are lacking. PurposeThe purpose of this in vitro study was to evaluate the effect of scanning speed, scanning pattern, and scanner tip size on scanning trueness and precision. Material and methodsA total of 120 complete arch intraoral scans were made with an intraoral scanner (Emerald). The 3 variables were tip size (small and regular), scanning pattern (occlusal first and S-shaped), and scanning speed (slow, regular, and fast). Ten scans for each variable combination were made and exported as standard tessellation language (STL) files. A laboratory scanner (E4) was used for the reference scan. The exported images were analyzed with an image analysis software program (Geomagic Control X). Root-mean-square deviation (RMSD) values between the intraoral scans and the reference scan were calculated to assess trueness. RMSD values between each intraoral scan were calculated to assess precision. Three-way analysis of variance (ANOVA) was used to evaluate the influence of each variable, and Tukey HSD tests were used for multiple comparisons (α=.05). ResultsFor trueness evaluation, tip size was the only significant factor (P<.001). The scans made with a smaller tip showed lower trueness than the scans made with a regular tip. For precision evaluation, all 3 variables, tip size, scanning speed, and scanning pattern, had significant influence (P≤.001). The use of a small tip, fast scanning speed, and S-shaped scanning pattern made intraoral scanning less precise. ConclusionsThe use of a small scanner tip negatively affected both trueness and precision. Fast scanning speed and S-shaped scanning pattern produced scans with lower precision than regular or slow scanning speed and the occlusal-first scanning pattern.

Pure tantalum manufactured by laser powder bed fusion: Influence of scanning speed on the evolution of microstructure and mechanical properties

To improve the performance of pure tantalum manufactured by selective laser melting (SLM) and meet its application requirements in medicine and industry, this paper studied the influence of SLM process parameters on the as-built surface morphology and mechanical performance, and successfully obtained a sample with a relative density of over 99%, ultimate tensile strength of 706Mpa and fracture elongation over 32%. It's found that the scanning speed has a significant influence on the microstructure. Moreover, the fractured morphology shows that it is easy to cause cracks at the lower energy density. However, at a higher energy density, it is easy to induce defects such as keyhole induced pores. The appropriate process parameters of additive manufacturing matching the pure tantalum with higher relative density and better mechanical properties have precious value for its application in medicine and industry.