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Microstructure and hardness evolution of laser metal deposited AA5087 wall-structures
摘要： Wire-based laser metal deposition enables to manufacture structures with very high deposition rates in comparison to powder-based laser additive manufacturing. However, this advantage is generally accompanied with a high energy input. Thus, an accumulation of heat within the structure can result. In addition, the heat conduction conditions can also change with increasing structure height, leading to inhomogeneous microstructural formation along the part. The present study deals with the evolution of the microstructure and hardness in laser metal deposited AA5087 wall structures. In this regard, two samples processed at adapted parameters for different deposition rates are investigated.
关键词： aluminum alloy,microstructure,laser additive manufacturing,microhardness,laser metal deposition
更新于2025-09-12 10:27:22
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Investigation on Ti6Al4V laser metal deposition using Taguchi based grey approach
摘要： An optimization of laser metal deposition process considering tensile strength, clad hardness, clad grain size and clad porosity as performance characteristics were investigated. The influence of laser power and laser scan speed on the thermal gradient and cooling rate with regard Ti6Al4V powder coating on Ti6Al4V substrate was focused. Taguchi’s experimental design approach is employed for planning the experiments and analyzing the dependency of input variables on desired performance measures such as micro hardness, tensile strength, porosity and grain size. The laser scan speed is found as the dominant factor on the clad hardness while laser power has the influencing effect on grain size of the substrate. GRA is opted for determining the multi performance machining characteristics of laser metal deposition process. The experimental outcomes reveal that the proposed method of multi objective optimization considerably enhances the multi performance machining characteristics.
关键词： Laser metal deposition,Ti6Al4V,Grain size,Thermal gradient,Grey relational approach,Laser scan speed
更新于2025-09-12 10:27:22
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Effect of laser power and deposition environment on the microstructure and properties of direct laser metal-deposited 12CrNi2 steel
摘要： Direct laser metal deposition was used for preparing blocks of steel 12CrNi2 using four different laser powers under two different deposition environments including atmospheric environment and Ar-protected chamber. The results showed that microstructures and mechanical properties were significantly affected by different laser powers. Increasing laser power and deposition in Ar chamber will lead to a decrease in the quantity and size of the voids, which brings more elongation to the samples. Bainitic microstructure was replaced by Widmanstatten ferrite and pearlite, and the amount of proeutectoid ferrite increased with increasing laser power. Moreover, microstructures of previous layers were completely altered in high laser power. Excessive heat accumulation by using high heat input can produce equiaxed ferritic grains with the pearlites in previously deposited layers. Hardness of deposited samples increased from the bottom layer toward the top layer. By using a diode laser with a spot diameter size of 2 mm, the 900-W laser power is suitable for producing crack- and void-free samples. However, post-deposition heat treatment is necessary for obtaining homogeneous desired microstructure and grain size in the manufactured samples.
关键词： Rapid solidification,Microstructure,Mechanical properties,Equiaxed ferrite,Direct laser metal deposition,Void,Bainite,Steel
更新于2025-09-12 10:27:22
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In-process height control during laser metal deposition based on structured light 3D scanning
摘要： Laser metal deposition is an additive manufacturing process capable of layer by layer construction of solid parts. An incorrect deposition distance between nozzle and substrate can result in height deviations from the ideal building path. The error can be propagated along layers, leading to an irreversible defect. Maintaining an optimal distance between the nozzle and the substrate is therefore a critical aspect. This paper introduces an off-line geometric control system for in-process measurement and build path correction. A structured light based 3D scanner measures the build height from an external, fixed position, providing more precise results than moving measuring systems. The deposition is stopped in certain stages of the process and the piece is scanned generating a three-dimensional point cloud. Processing of the collected data allows the build height determination. A control algorithm was developed to take corrective actions in accordance with the measured error. The system enables an accurate control of the generated geometry and permits the comparison with the original computer design. This approach reduces the required human supervision during the process and the occurrence of non-valid parts. The effectiveness of the method was proved through the contrast of parts built with and without control, showing a more accurate reproduction of the generated solid parts when corrections are applied.
关键词： monitoring,Laser Metal Deposition (LMD),additive manufacturing,control,metrology,structured light,3D scanning
更新于2025-09-12 10:27:22
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Laser metal deposition of bionic aluminum supports: reduction of the energy input for additive manufacturing of a fuselage
摘要： Additively manufactured components made of metallic material are subject to special consideration for many R&D departments, since the process control is not yet sufficiently reliable and therefore an extensive quality assurance is necessary. For this reason, few structural components for aviation have been established so far. In this paper, a feasibility study for the use of laser metal deposition (LMD) for the additive manufacturing of a fuselage made of aluminum is carried out. The result is a parameter set with a minimized energy input. However, due to a welding length of 58 m the overall energy input is high and large distortion arises.
关键词： aluminum,additive manufacturing,laser metal deposition,aerospace,bionic
更新于2025-09-12 10:27:22
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Influences of process conditions on stability of sensor controlled robot-based laser metal deposition
摘要： Robot-guided Laser Metal Deposition (LMD) process offers an efficient and resource-friendly production of big complex metals parts. In order to produce high-quality parts with minimum post-processing time, a highly stable process is required. The LMD process is characterized by numerous influencing physical parameters that lead to melt-pool instability, which results in shape irregularities in the component, followed by longer post-processing time. For process stability, control systems are necessary, which react to the occurring process and part deviations. The harsh environmental and process conditions impose high mechanical and thermal stresses on the sensors, which impact the accuracy of the system. In this paper, the factors influencing the accuracy of the sensors have been presented. The usability and stability of geometry control strategies with sensors have been evaluated against strategies without sensors. Additionally, the sensor system requirements for irregularity detection have been reported along with the guidelines developed for the implementation of a robust sensor control system for robot-based LMD processes.
关键词： Structured Light Sensor,Geometry Control,Sensor-Robot Control System,Sensors,Laser Metal Deposition
更新于2025-09-12 10:27:22
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Analysis of distortion during laser metal deposition of large parts
摘要： Laser Metal Deposition (LMD) of large parts is very challenging technology for aerospace industry. Due to high productivity of several kilograms per hour and nearly unlimited part size, this technology becomes competitive to traditional production technologies of casting, welding and rolling. One of the main problem of large parts manufacturing is the high distortion. Estimation of residual stresses and distortion is necessary to obtain required dimensional accuracy and prevent fracture of additively manufactured parts. Effects of layer-by-layer evolution of stresses and strains was studied by finite-element simulation. It was shown that distortion of axially symmetrical parts can be successfully predicted by the developed simulation procedure. It was established that the effect of increasing cylinder radius is to increase residual radial displacement and curvature of the sidewall. The highest tension hoop and axial stress amounted to 1.15-1.2 times of yield stress near the substrate. If deposited material have a weak ductility (e.g. titanium alloys) there is a high probability that the fracture could occurs in the sidewall near the substrate. Several experimental trials was carried out for validation of accuracy of developed simulation procedure. Shape of build parts was analysed by 3D laser scanner.
关键词： residual stress,laser metal deposition,distortion,finite element method.
更新于2025-09-12 10:27:22
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Laser metal deposition of Ti-6Al-4V alloy with beam oscillation
摘要： One of the most prevalent problems of additive technologies is the improvement of process efficiency at the expense of increase in mass deposition rate and reduction of postprocessing time. Deposition rate can be improved by the modification of the shape and size of the molten pool through the optimization of laser beam power distribution. Time and cost of postprocessing depend on the surface roughness requirements and presence of macroscopic waviness. Beam oscillation can help to solve this problem. Laser metal deposition with linear beam oscillation was studied. Effects of numerous process parameters on pool shape and size was analysed by simulation. The heat conduction problem was solved analytically by Green’s function method. Temperature fields due to moving normally distributed strip heat sources were studied. It was established that on increasing the oscillation amplitude up to laser beam radius the heat flux of normally distributed strip heat source decrease rapidly to 53%. Greater the beam radius, the less effect of amplitude on the peak value of molten pool width and lower allowable oscillation amplitude. Microscopic examination revealed that beam oscillation promotes obtaining smooth wall surface without any macroscopic waviness.
关键词： surface waviness,titanium alloy,beam oscillation,temperature field,laser metal deposition
更新于2025-09-12 10:27:22
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Additive manufacturing of tool steel by laser metal deposition
摘要： In this work, different geometries were additively manufactured applying laser metal deposition using powder out of hot-working tool steel 1.2344. It was shown that this hot working tool steel can be used to manufacture crack free parts through laser metal deposition. Temperatures were locally measured in experimental investigations. Additional microstructure analysis of different geometries indicated a dendritic solidification structure and grain boundary carbides. Vickers hardness varied between 400 HV 1 and 750 HV 1.
关键词： intrinsic heat treatment,1.2344,additive manufacturing,laser metal deposition,hot work tool steel,dilatometer specimen
更新于2025-09-12 10:27:22
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Laser metal deposition of lattice structures by columnar built-up
摘要： Independent of the geometrical complexity of a laser metal deposition component, the fundamental geometrical element is given by basic weld seams most of the times. These weld seams are deposited on a surface area and therefore not suitable to generate lattice structures. In this study, it is successfully demonstrated that basic spot welds can be used to achieve a vertical columnar built-up of pillars. Tilting of these pillars was used to merge them or to form forks. In that way, laser metal deposition of a lattice structure was implemented.
关键词： spot weld,pillars,laser metal deposition,lattice structure,branched structure
更新于2025-09-12 10:27:22