Increase Of Scanning Speed Research Articles

Microstructure, mechanical properties and corrosion behavior of additively-manufactured Fe–Mn alloys

In this paper, we describe the effects of different scanning speeds (600–900 mm/s) on the microstructure, mechanical properties and corrosion behavior of biodegradable bone-substitution alloys produced from 80:20 (by wt.) Fe:Mn powders using laser powder bed fusion (LPBF). Both the Mn content (18.9–15.1 wt% Mn) and density (7920–7730 kg/m3) of the LPBFed samples decreased slightly with increasing laser scanning speed, while the oxygen content increased (0.12–0.40 wt%). Increasing scanning speed also led to increased porosity (from 0.27% to 2.5%) and increased cracking. The specimen produced at the lowest scanning speed of 600 mm/s, which consisted of only the HCP ε-martensite phase, showed by far the highest yield strength (YS) at 644 MPa and the highest ultimate tensile strength (UTS) at 857 MPa, but the lowest elongation to failure (El) of only 13.7%. Specimens produced at higher scanning rates consisted of both BCC α′-martensite and ε-martensite phases. The sample fabricated at a scanning speed of 700 mm/s showed the best balance of mechanical properties with a YS of 330 MPa, a UTS of 839 MPa, and an El of 36.1%. Electrochemical testing showed corrosion rates from 0.09 mm/yr (600 mm/s specimen) to 0.22 mm/yr (700 mm/s specimen), which are higher than those of both pure Fe and most Fe–30Mn and Fe–35Mn alloys reported in the literature. The work demonstrates that the meso-/micro-scale structure, and, hence, the mechanical properties and corrosion rates of Fe–Mn alloys can be tailored by varying the scanning speed during LPBF processing. It also demonstrates the potential of LPBFed Fe–Mn alloys with low Mn content for use as biodegradable bone substitutes.

Cracks and process control in laser powder bed fusion of Al-Zn-Mg alloy

Al-Zn-Mg alloy is receiving a growing number of attentions due to the strategic demand in the aerospace industry. But crack is a headache problem in Al-Zn-Mg alloy fabricated by Laser Powder Bed Fusion (LPBF). This paper investigated the characteristics, formation mechanisms and process control of the cracks in LPBF fabrication of Al-3.6Zn-0.6Mg alloy. Cracks in LPBF fabrication of Al-3.6Zn-0.6Mg alloy were found to be solidification cracks. Solidification cracks were initiated by fracture of Mg contained liquid film. Fracture of liquid film was because the pressure drop reached the critical pressure. The pressure drop increased with the increase of scan speed and decrease of laser power. Small pressure drop is helpful to reduce crack susceptibility. Crack-free Al-3.6Zn-0.6Mg alloy were fabricated by reducing scan speed and increasing the laser power. The optimized laser power was 490 W, scan speed was 400 mm/s, scan space was 0.08 mm, laser focus shift was −3.5 mm. Crack-free Al-3.6Zn-0.6Mg alloy exhibited a tensile strength of 306.7 ± 7.4 MPa, yield strength of 214.3 ± 3.1 MPa and elongation of 5.5 ± 1 %. The study gives a direction to control the solidification crack in LPBF fabrication of Al-Zn-Mg alloy.

Inclined shaping quality and optimization of laser cladding

Inclined repairing was used to explore the effects of laser cladding process parameters on the shaping properties of multi-pass cladding on an inclined plane in the work. The results showed that the coating area increased with increased laser power and overlap rate and decreased with the increased scanning speed. Besides, it first increased and then decreased with the increased feeding voltage. The dilution rate increased with increased laser power and scanning speed and decreased with increased overlap rate. Meanwhile, the rate first decreased and then increased with the increased powder feeding voltage. Flatness increased with increased laser power and overlap rate and decreased with the increased scanning speed and feeding voltage. Fitted mathematical models were subjected to multi-objective optimizations by the NSGA-II algorithm and response optimizer, respectively. The optimized results obtained by the response optimizer were better, while those obtained by the NSGA-II algorithm were more diversified.

An effective method for large-scale temperature simulation in SLM based on the finite difference

Numerical simulation is an effective approach to analyze the selective laser melting (SLM) process and reduce the production development cost. Based on the finite difference method (FDM), the nonuniform grid algorithm (NUGA) is developed to simulate the thermal behavior in SLM process concerning the variable thermophysical parameters of materials with different status. The NUGA can effectively improve computing efficiency, and the calculation speed using NUGA is 610 times than that without using NUGA. Different heat transfer strategies are used on each side of the two critical scanning speeds, 68.95 mm/s and 6895 mm/s, respectively, and the results of temperature calculations are highly consistent. The correctness of the heat transfer strategy under different speeds is analyzed using the NUGA. The effects of processing parameters (laser power, scanning speed and building height) on the shape and volume of the molten pool are investigated. As the scanning speed ranged from 100 mm/s to 500 mm/s, the width and depth of the molten pool decrease, while the length increases. As the laser power ranged from 100 W to 500 W, the length, width and depth of molten pool all increase. The length of the molten pool increases 11.68% from 264.94 of layer 1 to 295.88 of layer 5. The molten pool volume decreases, then increases and decreases finally from the start to the end of single molten path. The molten pool volume increases with increasing laser power and building height, while decreases with increasing scanning speed in general. The NUGA is an effective method for temperature simulation of large-size parts, which expands the application range of temperature simulation in SLM process.

Surface laser processing of maraging steel parts manufactured by selective laser melting: effect on pass geometry and hardness

Due to the possibility to produce the parts with complex internal and external geometries, selective laser melting (SLM) process attracts growing interest in various fields of engineering segments such as aircraft, aerospace, biomedical, automotive, marine industries and tooling. Maraging steels, having excellent weldability and high resistance to thermal fatigue due to the lack of carbon, has showed good suitability for SLM [1]. However, owing to the limited hardness and wear resistance, maraging steels has limited application at the harsh wear conditions [4]. In this study, the possibility to improve the surface characteristics of DIN 1.2709 steel SLM parts by application of laser alloying technology is evaluated. The surface of SLM part was laser processed at various laser spot diameters and varying laser scanning speeds from 500 to 1500 mm⋅min-1, with and without preposition of alloying element. The power density was provided in the range from ~0.8⋅103 W⋅cm-2 to ~51⋅103 W⋅cm-2 and heat input – from 4 to 12 J⋅mm-1. The effect of laser processing parameters and presence of alloying element on the geometry of obtained processed passes and hardness of surface was evaluated. It was determined, that the application of CO2 continuous laser at the parameters of 1 kW laser power, 0.5 mm laser beam spot diameter and laser scanning speed in the range between 500 mm⋅min-1 and 1250 mm⋅min-1 allows obtaining laser pool of acceptable geometry and sizes directly on as-manufactured SLM part surface without any pre-processing. The increasing scanning speed to 1500 mm⋅min-1 or spot size to 2.0 and 3.0 mm results in too small pool depth and unstable pool geometry. The laser processing with preposition of alloying element layer provided surface alloying effect of the maraging steel SLM part. The hardness of processed surface areas ranged between ~600 HV0.2 at the lowest scanning speed and ~1770 HV0.2 at the highest speed, what is from 18% to ~3.5 times higher, as compared with maximum hardness of 1.2709 maraging steel after aging (~58 HRC or ~510 HV).

Cross-Scale Simulation Research on the Macro/Microstructure of TC4 Alloy Wire Laser Additive Manufacturing

A cross-scale model of macro-micro coupling is established for the wire laser additive manufacturing process of the TC4 titanium alloy. The model reproduces the dynamic evolution process of the molten pool shape, reveals the temperature change law in the molten pool, and simulates the microstructure and morphology of different regions of the molten pool. Finally, the model is used to quantitatively analyze the effects of process parameters (laser power, scanning speed) on the growth morphology of dendrites during solidification. The research shows that with the increase in laser power and the decrease in scanning speed, the peak temperature of the molten pool increases rapidly, and the size of the molten pool increases gradually. When the laser scanning speed is greater than 5 mm/s, the molten pool length decreases significantly. After solidification, an asymmetrically distributed equiaxed grain structure is formed at the upper part of the molten pool, the bottom of the molten pool is made up of slender columnar crystals, and the columnar-to-equiaxed transition (CET) occurs in the middle of the molten pool. With the decrease in laser power and the increase in scanning speed, the growth rate of dendrites becomes faster, the arm spacing and the overall morphology of dendrites become smaller, and the arrangement of columnar crystals have a tighter microstructure.

Performance and efficiency control method of in-situ TiC generated by laser cladding

The work studied the effects of differences in the molar ratios of carbon to titanium on the performance and forming efficiency of in-situ TiC materials generated by laser cladding. The full factor test method was used to explore the coupling effect of process parameters on the hardness of the cladding layer and the formation efficiency of TiC. The combined-parameter method was used to establish the mathematical models of laser power, scanning speed, powder ratio versus hardness, hard-phase production, and cladding efficiency. The results showed that the hardness and hard-phase formation increased with increased laser power and powder ratio and decreased with the increased scanning speed. The cladding efficiency increased with increased laser power and decreased with the increased scanning speed and powder ratio. With the low molar ratio of carbon to titanium, TiC in the form of dendrites was found in the cladding layer. When the carbon-titanium ratios were close and carbon was surplus, the morphology of the generated TiC particles was petal-like and spherical. Besides, the production increased and grain had finer sizes. Sensitivity analysis showed that fine adjustment of the powder ratio significantly affected the three models with the laser power of 1800 W, a scanning speed of 4 mm·s−1, and a powder ratio of 0.7, and the accuracy of the sensitivity analysis was proved through experiments.

Grain-based morphological simulation via fractal theory with experimental verification and corresponding optical properties in laser melting deposition additive manufacturing: A demystified approach

Laser melting deposition (LMD) stands for a challenging and promising 3D printing technology to fabricate near-net-shape parts. In this study, a 3D modified fractal model (3DMFM) has been developed by considering the surface texture orientation in the technical manufactured surfaces. Fractal parameters, including fractal dimensions and periodic lengths in the 3DMFM, have been solved for the grain-based morphologies developed by LMD. In combination with statistical parameters, these fractal parameters were applied in 3DMFM for analytical simulations. Single-track depositions of AISI 304 stainless steel powder on AISI 304 stainless steel substrate were subjected to scanning electron microscopy investigations for experimental validation of the proposed model. A customized investigational setup, having a He-Ne laser system (632.8 nm and 7.75 mW), was designed to identify the optical properties of each deposited layer. Three types of grains were identified: round quasi-continuous (RQC), elongated lath-shaped (ELS), and a combination of the two. The RQC grains were transformed into ELS grains with an increment in laser scanning speed. The RQC and ELS combination was converted into RQC grains with an increase in the powder feeding rate. RQC changed into ELS grains whenever the laser power was elevated. An increase in skewness and a decrease in kurtosis were observed whenever laser scanning speed or powder feeding rate was increased. A laser power amplification also determined a rise of skewness and a reduction in the kurtosis values. A rise in either laser scanning speed or powder feeding rate lowered the surface roughness, while an inverse correlation was observed between laser power and surface roughness. An increase in laser scanning speed or laser power increased the fractal dimensions (Dx and Dy). However, the powder feeding rate was inversely correlated with Dx and Dy. In the case of periodic lengths (Lx and Ly), the scanning speed, powder feeding rate, and laser power exhibited an inverse behavior with Dx and Dy. Larger magnitudes of Dx or Dy were resulted due to an increased optical reflection or a decreased optical absorption, while the opposite results were attained in the case of periodic lengths inclination (Lx and Ly). The developed fractal model can predict and select the best LMD process parameters in terms of quality control and time/cost-effectiveness.

Biomedical porous scaffold fabrication using additive manufacturing technique: Porosity, surface roughness and process parameters optimization

Titanium is a most common and best biocompatible material. The demand and application of Ti alloy is increasing rapidly in orthopedics for clinical operations. The porous structures have been designed for bone tissue engineering or orthopedic applications due to its moderate Young's modulus, excellent compressive strength, biocompatibility and sufficient space for cell accommodation. The porous scaffolds with individual complex internal and external shape can be manufactured by additive manufacturing (AM) processes especially selective laser melting (SLM), both of these have great importance for repairing of large sectional bone defects. This advantage makes the SLM process one of the most competitive AM processes used in the biomedical fields. Seven different Ti–6Al–4V porous scaffolds (Diamond, Grid, Cross, Vinties, Tesseract, Star and Octet) of 15 mm cube with 65% porosity were designed using Rhino 6 software and fabricated through SLM using Ti–6Al–4V powders. This work mainly focused on porous scaffolds design and manufacturing by AM particularly SLM, can able to produce scaffolds of nanoscale grains because of its higher heating rate and lower holding time. But this process generally results insufficient compaction where desired function is not achieved. The scaffolds manufactured by SLM have relatively high accuracy of pore structure and low mechanical strength. Grid type structure exhibits lower surface roughness value and better manufacturing ability where error percentage of porosity is lower than the other scaffolds.The process parameters employed in the study like laser power, scanning speed, hatch distancing and layer thickness are the most significant factors that influence the defect behaviour and morphology of the SLM-fabricated samples. Porosity percentage and surface roughness of the scaffold palys a vital role on its desired functions. While the porosity percentage are also effected by input process parameters resulting the variation on effective elastic modulus. The increase in scanning speed leads to elevation of the cooling rate, which results in a finer microstructure. On the other hand, with lower scanning speeds, coarse microstructure is observed.

Effects of Process Parameters on the Relative Density and Properties of CuCrZr Alloy Produced by Selective Laser Melting

CuCrZr alloy has the advantages of good electrical conductivity, thermal conductivity, high hardness, crack resistance and high softening temperature. It is extensively used in important fields such as rail transit, aerospace, thermonuclear fusion and electronic information. Due to its high melting point, reflectivity, thermal conductivity, etc., it is more difficult to manufacture by selective laser melting (SLM). In this work, the effect of SLM process parameters on the characteristics of CuCrZr samples, such as relative density, hardness and tensile properties, has been investigated using orthogonal experiment method. The experimental results show that laser power is the main factor affecting the properties of the alloy. The tensile strength of the alloy increases with an increase in laser power; it first increases and then decreases with an increase in scanning speed. The optimal combination of process parameters in this paper is as follows: laser power is 240 W, scanning speed is 750 mm/s and scanning spacing is 0.07 mm. The relative density, ultimate tensile strength and hardness of the alloy fabricated by best SLM process parameters was 98.79%, 347 MPa, 133.9 HV, respectively.

Orientation-Dependent Indentation Behaviour of Additively Manufactured FeCo Sample: A Quasi In-Situ Study

The quasi in-situ indentation behaviour of <110>||BD and <111>||BD-oriented grains in a FeCo alloy is studied in this investigation. The effect of build height on melt pool shape and melt pool size is also studied by finite element method simulations. As the building height increases, the aspect ratio of the elliptical melt pool increases. Correspondingly, the effect of the laser scan speed on the melt pool shape and size is studied by the finite element method, because, as the laser scan speed increases, the aspect ratio of the elliptical melt pool increases, too. The microstructural characterisation of the indentation area before and after indentation is performed by electron backscatter diffraction (EBSD). Based on the EBSD data grain reference orientation deviation (GROD), calculations are performed to describe the effect of indentations on the neighbouring grain orientations. High GROD angles are detected in the neighbouring grain region adjoining the indented grain. An in-depth slip trace analysis shows the activation of all three slip systems ({110}<111>, {112}<111> and {123}<111>) which is also confirmed by slip lines on the sample surface that are detected by laser scanning confocal microscopy. A high concentration of geometrically necessary dislocations (GNDs) are observed on the adjoining area to the indentation. Local surface topography measurements by laser scanning confocal microscopy confirmed the formation of pile-ups near the indentation.

A comprehensive study on the effect of line energy during laser bending of duplex stainless steel

Laser bending is a well-established process to achieve bending with high accuracy and good controllability. This study discusses the effect of line energy on bending mechanism, bend angle, edge effect, mechanical properties, and microstructural characterization for laser bending of duplex stainless steel. Numerical simulations have been carried out for a better understanding of the bending mechanisms. Additionally, the role of temperature distribution at the bottom surface on the variation in bend angle has been analyzed. It is found that at low laser powers, the bend angle increases with line energy, but at a decreasing rate. Whereas at high laser powers, the bend angle increases with line energy; attains peak and then decreases. At constant line energy, the bend angle increases with the increase in laser power and scanning speed. The hardness of laser-scanned specimens is increased, and ductility is reduced. Besides, the ultimate strength and yield strength remain almost constant. The sigma phase formation has been observed during the microstructural analysis, which further correlates with the high hardness and low ductility.

Effect of processing parameters on formability, microstructure, and micro-hardness of a novel laser additive manufactured Ti-6.38Al-3.87V-2.43Mo alloy

A novel Ti-6.38Al-3.87V-2.43Mo alloy was designed with a cluster formula of 12[Al-Ti12] (V0.75Mo0.25Ti2)+4[Al-Ti12](Al3) by replacing Ti with Mo/V on the basis of the Ti-Al congruent alloy. The effects of laser power and scanning speed on the molten pool size, surface roughness, relative density, microstructure, and micro-hardness of single-track and bulk Ti-6.38Al-3.87V-2.43Mo samples prepared via laser additive manufacturing (LAM) were investigated. The results show that processing parameters significantly affect the formability, microstructure, and micro-hardness of the alloy. With decreasing laser power from 1,900 W to 1,000 W, the relative density is decreased from 99.86% to 90.91% due to the increase of lack-of-fusion; however, with increasing scanning speed, the relative density does not change significantly, but exceeds 99%. In particular, Ti-6.38Al-3.87V-2.43Mo samples of single-track and bulk exhibit a good formability under an input laser power of 1,900 W and a scanning speed of 8 mm·s-1, and display the lowest surface roughness (Ra=13.33 µm) and the highest relative density (99.86%). Besides, the microstructure of LAM Ti-6.38Al-3.87V-2.43Mo alloy coarsens with increasing laser power or decreasing scanning speed due to the greater input energy reducing the cooling rate. The coarsening of the microstructure decreases the microhardness of the alloy.

Processing and Profile Control of Microhole Array for PDMS Mask with Femtosecond Laser.

Polydimethylsiloxane (PDMS) is hailed as one of the foundational materials that have been applied to different products in various fields because of its chemical resistance, low cost, excellent flexibility, and high molding capability. With the aim to achieve surface texture with high efficiency by means of electrochemical micromachining with PDMS mask, a femtosecond laser is utilized to process a precision array of micro-through-holes on PDMS films as the molds. The ablation process of PDMS with a femtosecond laser was investigated via numerical simulation verified with experiments indicating a laser energy density of 4.865 mJ/mm2 as the ablation threshold of PDMS with the melting temperature of 930 K. The spiral scanning path with optimized radial offset was developed to ablate materials from the PDMS film to form the laminated profiles, and a tapered through hole was then formed with multilayer scanning. The profile dimension and accuracy were examined as control targets in terms of laser pulse energy and scanning speed, showing that a 12 μJ femtosecond laser pulse energy and 1000 mm/s scanning speed could bring about a nearly circular laminating profile with expected smaller exit diameter than the entry diameter. All the cross-section diameters of the microcone decreased with the increase of laser scanning speed, while the taper increased gradually and then saturated around a laser scanning speed of 800 mm/s due to the energy absorption resulting in smaller ablation in diameter and depth.

Effect of laser scanning speed on the microstructure, phase transformation and mechanical property of NiTi alloys fabricated by LPBF

This study investigated the effects of laser scanning speed on the microstructure, phase transformation and properties of NiTi alloys fabricated by laser powder bed fusion (LPBF). In this study, the contributions of metallurgical factors under different scanning speeds, such as Ni evaporation, Ni4Ti3 precipitation, dislocations and internal stress, to the transformation temperature and transformation latent heat were clarified through specially designed experiments. Ni evaporation is found to have the most profound effect, followed by precipitation. Increasing scanning speed is found to reduce Ni loss, thus cause less increase in the transformation temperature and transformation heat of the LPBF-NiTi alloys. Increasing scanning speed also increases the microstructure non-uniformity and thus widens the transformation temperature interval. The orientations of residual stress exhibit strong crystallographic stiffness dependence. The LPBF-NiTi alloys with different scanning speeds all exhibited high strains (>13.4%) and excellent shape memory effect. A LPBF-NiTi honeycomb structure exhibited 96% shape recovery rate after a 60% pre-compressive deformation. Besides, there is an optimum scanning speed for minimum porosity and smallest average pore size. However, the pore structure is found to have weak influence on the tensile behaviour of the LPBF-NiTi alloys, possibly due to the high defect tolerance of the martensitic transformation.

Selective laser melting of Al–Si–10Mg alloy: microstructural studies and mechanical properties assessment

Additive Manufacturing (AM) technique is widely recognized by aerospace sectors for its potential to fabricate complex shape components directly from a Computer-Aided Model data (CAM). Selective Laser Melting (SLM) is an innovative method high degree of adaptability among different AM techniques. SLM is one of the AM techniques adopted to produce the three-dimensional complex shape components. Current research work focuses on fabricating an Al–Si–10Mg aluminium alloy by SLM process which is studied for the influence of scanning speed and build orientation on the mechanical strength and surface finish of the as built component compared with as casted specimen. The importance of the sample studied for the scanning speed and built direction is relatively essential exclusively for dynamic applications. The as-built samples surface micrographs was surprisingly refined with a progressively reduced grain size diameter from 7.2 μm to 5.5 μm by increasing scanning speed compared to that of AlSi10Mg parts (∼9.1 μm). The mean layer thickness increased from 20 μm to 30 μm by decreasing the scanning speed from 500 mm/s to 200 mm/s. Attractive advantage of the Orowan mechanism, fine grain strengthening, and the graded interfacial layer, a considerably-high microhardness (135 ± 3.1HV), and enhanced mechanical properties were achieved.

Experimental investigation and optimization of femtosecond laser processing parameters of silicon carbide–based on response surface methodology

The femtosecond laser, with its extremely high peak power and ultrashort pulse duration, is widely used in silicon carbide (SiC) processing. Herein, the response surface method was used to develop four quadratic regression models to predict the groove depth, width, heat affected zone (HAZ), and material removal rate (MRR). The effects of each parameter were investigated using variance analysis. In addition, the interaction of processing parameters with groove depth, width, HAZ and MRR was investigated, which provided an important analysis for the precise selection of processing parameters. The laser fluence is shown to significantly impact the groove depth, width, HAZ, and MRR. The scan speed significantly influences the groove depth, width, and HAZ but not the MRR. The repetition rate and multipass scanning significantly influence the groove depth, HAZ, and MRR but only moderately influence the groove width. The models show that changing the energy received by the groove can change the groove depth, width, HAZ, and MRR. The groove depth, width, and HAZ increase as the laser fluence, repetition rate, and multipass scanning increase; and they decrease as the scan speed increases. The MRR increases as laser fluence and multipass scanning increase. Meanwhile, the MRR varies slightly with repetition rate and scan speed. A nonlinear functional relationship exists in the interaction process of processing parameters. The processing parameters were optimized using response surface methodology with the maximum MRR and minimum HAZ as the objective function. Within the range of the processing parameters used, the average relative error between the experimental and predicted values was less than 5%. Consequently, the established regression models can accurately predict the groove depth, width, HAZ, and MRR in SiC femtosecond laser processing.

Densification Behavior and Microstructures of the Al–10%Si–0.35Mg Alloy Fabricated by Selective Laser Melting: from Experimental Observation to Machine Learning

This work examined the behaviors of densification and microstructural formation of the Al–10 mass%Si–0.35 mass%Mg alloy fabricated by Selective Laser Melting (SLM) method on the basis of experimental work and machine learning. Additionally, the effect of scanning repeated twice in each layer (double scanning) in the SLM process was also investigated. The SLM-ed Al–10 mass%Si–0.35 mass%Mg alloy exhibited the columnar grained microstructure with a (α-Al–Si) eutectic cell structure. Refined microstructures were produced at an increasing scanning speed with a decreasing the energy density (J/mm3). Relative density tended to increase with an increasing of energy density for scan pitch conditions of 0.1 mm and 0.05 mm. And a scattering was obviously exhibited at a higher relative density more than 95%. The analysis based on machine learning revealed that a scanning pitch of 0.2 mm was just a condition to achieve a high relative density. Except for the condition at a scanning pitch of 0.2 mm, a scan speed was the most important factor in affecting the relative density. Thus, a machine learning approach enabled to identify the important processing factor for affecting the behavior quantitatively. Additionally, compared to a conventional single scanning process, it was found in this work that the double scanning resulted in a higher relative density with keeping the fine microstructural formation.

Investigation on the effect of powder size on the properties of cladding layer based on RSM

This paper aims to reveal the influence of different TiC powder particle sizes and process parameters on the cladding morphology of composite materials and realize the forming control of cladding layer. The center composite design of response surface method was adopted to analyze the effects of laser power, scanning speed and particle size on the cladding morphology of composite materials. The mathematical models between process parameters, TiC powder particle size and micro-hardness, wear volume of the composite cladding layer were established and confirmed by variance analysis and model verification. The results indicate that powder particle size has most significant effect on the micro-hardness, and it increase with the increase of scanning speed, laser power and powder particle size; the effect of powder particle size on the wear resistance of the clad layer is most significant, and it increases with the increase of powder particle size and decreases with the increase of scanning speed and laser power. The optimization of process parameters is carried out with the target of maximizing micro-hardness and minimizing wear area. The error rates between prediction and experiment for the micro-hardness and wear area are 0.1% and 2.0% respectively. The results of this paper provide a reference for the prediction and control of the cladding morphology of composite materials.

Single and multiple track formation mechanism of laser powder bed fusion 316L/CuSn10 multi-material

This paper focuses on the influence mechanism of process parameters on the geometry morphology and microstructure characteristic of single-track and multi-track 316L/CuSn10 multiple materials manufactured by laser powder bed fusion (LPBF). The width of single-track increases with the increase of laser power and layer thickness, and decreases with the increase of scanning speed. Both variations in the copper content and wetting angle of the molten pool were investigated. In addition, the comparison of defect characteristics shows that the scanning speed and layer thickness have a greater influence on the formation of single cracks. The traces of Marangoni convection are observed directly in the centre of the molten pool due to the difference in microstructure between 316L and CuSn10 alloys. It is found that the copper penetration cracks appear on the steel side at the molten pool bottom. Moreover, fine grains appear in the copper-rich region, and the large-angle grain boundary distribution seems to be the reason for the concentration of dislocations. Four types of crack formation mechanisms are found in the cross section of the multi-track: crack formation inside the molten pool, passing through the track boundary, extending to the steel substrate, and copper penetration cracks.