- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
Epitaxy and new stray grain formation mechanism during epitaxial laser melting deposition of Inconel 718 on directionally solidified nickel-based superalloys
摘要： The epitaxy behavior and stray grains (SGs) formation in the deposit during epitaxial laser melting deposition (E-LMD) of directionally solidified (DS) superalloys were investigated. Columnar dendritic structures were obtained by epitaxial solidification on the DS substrate. The deposit also remained the orientation of the substrate. The SGs at the fusion interface, which were hardly eliminated, were attributed to different SGs formation mechanisms. The SGs were divided into GB-SGs and MC-SGs by the distribution characteristics. The GB-SGs at the low-angle and high-angle grain boundaries with a new mechanism of dynamic recrystallization induced by accumulation of thermal strain and stress under repeated spatially variable heating and cooling. The MC-SGs around the carbides were related to the misoriented cellular crystal formation caused by the varied shape of the solid-liquid interface. The columnar to equiaxed transition (CET) was another mechanism of MC-SGs formation.
关键词： Stray grain,Nickel superalloys,Laser metal deposition,Recrystallization,Dynamic,Epitaxy,Microstructure
更新于2025-11-28 14:24:20
-
Effects of phase transition temperature and preheating on residual stress in multi-pass & multi-layer laser metal deposition
摘要： To investigate the influences of phase transition temperature and preheating on the residual stress of multi-layer and multi-pass laser metal deposition (LMD), the multi-layer and multi-pass LMD, with and without preheating, were performed using five kinds of alloy with different phase transition features, and their residual stresses were measured using the hole drilling method. A finite-element (FE) model incorporating the phase transition was developed based on experimentally obtained physical property data. The results demonstrated that the low-temperature solid phase transition has a tensile stress relaxation effect, which leads to the formation of a compressive stress area. This relaxation effect was observed to decrease with the increase of the phase transition temperature. The high-temperature solid phase transition has no significant tensile stress relaxation effect during the multi-layer and multi-pass LMD process, which is different from the single track LMD. when the solid phase transition temperature is low, the preheating can improve the uniformity of the stress field only to a certain extent. However, when the preheating increases the lowest temperature of the thermal cycle and makes it higher than the starting point temperature of the solid phase transition, the tensile stress relaxation effect of the solid phase transition can be brought into full play.
关键词： Finite element analysis,Preheating,phase transition temperature,Residual stress,Laser metal deposition
更新于2025-11-28 14:24:20
-
Microstructural Characteristics of Laser Metal Deposited Magnesium Alloy AZ31
摘要： Up to now, only a limited amount of metallic materials is investigated for laser additive manufacturing (LAM). However, the demand to widen the application possibilities by enlarging the range of materials for LAM is growing fast. By now, titanium and aluminium alloys are in the focus of research. In contrast, magnesium alloys are rarely used in the field of additive manufacturing, although they possess a low density in combination with a high specific strength. Currently, magnesium structures are mainly produced by casting but during the last years, the use of wrought alloys also increased. A reason for the rare use of magnesium alloys for LAM technologies might be the high flammability of magnesium powders. This difficulty can be avoided by using magnesium wire for laser metal deposition (LMD). In the present study, the microstructural characteristics of a LMD processed AZ31 magnesium alloy are investigated. For this purpose, optical microscopy and scanning electron microscopy were used. With the help of EDX and EBSD analysis, a change of the chemical composition and micro texture with structure height was identified. The relationship of microstructure and local mechanical properties was investigated with the help of Vickers micro hardness testing. Based on the obtained results it can be concluded that the microstructural characteristics of laser additive manufactured magnesium alloys differ from those of titanium and aluminium alloys. Thus, a wider application spectrum of LMD and magnesium alloys can be opened up.
关键词： laser metal deposition,local mechanical properties,microstructure,magnesium alloy,wire,microtexture
更新于2025-11-28 14:24:20
-
Study on the element segregation and Laves phase formation in the laser metal deposited IN718 superalloy by flat top laser and gaussian distribution laser
摘要： The element segregation, Laves phase formation, and mechanical properties of the laser metal deposited IN718 superalloy by the flat top laser beam (FTLB) and gaussian distribution laser beam (GDLB) are studied. It is found that the Laves phase formation in the gaussian distribution laser deposited IN718 (GDLD-IN718) is substantially higher than that in the flat top laser deposited IN718 (FTLD-IN718). The higher production of the Laves phase in the GDLD-IN718 contributes to the higher microhardness and lower tensile strength (about 20% reduction) of the as-deposited IN718 than that of the FTLD-IN718. The element redistribution behavior in the laser rapid solidification under both of the lasers are also studied through the finite element simulation. The results show that the severe laser energy concentration in the center of the GDLB produces higher molten pool temperature, lower horizontal thermal gradient to vertical thermal gradient ratio (GX/GZ) of the solid-liquid interface. These typical thermal characteristic of the GDLB generated molten pool eventually results in a lower redistribution coefficient of the alloying elements and as a result, the interdendritic element segregation and Laves phase formation are dramatically improved in the GDLD-IN718. The present comparative study proves that the FTLB is more superior for the laser additive manufacturing than that of the GDLB.
关键词： Dendritic growth,Laser metal deposition,Element segregation,Redistribution coefficient,Laves phase
更新于2025-11-21 11:18:25
-
Cladding of Stellite-6/WC Composites Coatings by Laser Metal Deposition
摘要： This study aims to investigate the microstructure and hardness of multi-layered Stellite-6/WC metal-matrix composites coatings on metallic substrates cladded by laser metal deposition (LMD) for improvement of wear and corrosion resistances. As coating materials, Stellite-6 and WC-12wt.%Co powders were selected. Powder mixtures having various mixing-ratios of Stellite-6 and WC-12wt.%Co were provided vertically on S45C substrates by controlling powder feeding rates of the two powder feeders, individually. Stellite-6/WC composites which consist of three layers with different compositions were cladded on the S45C substrates by laser melting. Cross-sectional microstructure observation was carried out by using an optical microscope (OM). Vickers microhardness tests were conducted to evaluate hardness of the cladding layers and substrates. The experimental results demonstrate that hard multi-layered Stellite-6/WC metal-matrix composites coatings were successfully cladded on the S45C substrates. Property gradients in the Stellite-6/WC composites could be made due to the position-dependent chemical composition and microstructure made by controlling powder feeding rates of an LMD system.
关键词： Cladding,Additive Manufacturing (AM),Metal Matrix Composites (MMC),Laser Metal Deposition (LMD),Hard Materials
更新于2025-09-23 15:22:29
-
Analysis and design of coaxial nozzle with rectangular outlet for high power diode laser in laser metal deposition
摘要： High power diode laser (HPDL) characterized by a wider rectangle beam spot (RBS) with top-hat intensity distribution is particularly applied in laser metal deposition to manufacture large-scale components. In order to design a coaxial nozzle with rectangular outlet to match the RBS of the HPDL, a novel wide-beam coaxial feeding nozzle (WBCFN) outlet is proposed. Based on the gas-powder flow model established in ANSYS FLUENT, the influence of structural parameters of the new coaxial nozzle on the gas flow and powder distribution is investigated. Two quantitative indexes are defined to seek out the optimal designing scheme that minimize the divergences of the powder flow and uniform the powder distribution in transverse and longitudinal directions. And then, the effect and sensitivity of structural parameters on concentration distribution and focal length of powder flow are analyzed. The results indicate that the two indexes increase with the increase of exit width, while the variance of concentration firstly increases and then decreases with the increase of the chamber length and inclination angle. The focal length decreases with the increase of inclination angle. Finally, the optimal solution of designing scheme is obtained through comprehensive analysis, and experiments are carried out to validate the model, which indicates that the designed WBCFN can acquire good morphology and quality of deposition layer for HPDL.
关键词： Wide-beam coaxial feeding nozzle,Laser metal deposition,Discrete phase model,High power diode laser
更新于2025-09-23 15:21:01
-
Microstructure and properties of CeO2-doped CoCrFeMnNi high entropy alloy fabricated by laser metal deposition
摘要： Rare earth elements are usually regarded as e?cient additives for property enhancement of many types of alloys. In the present study, the CoCrFeMnNi high entropy alloy (HEA) was doped with CeO2, and such composites were for the ?rst time obtained by the laser metal deposition (LMD) process. The microstructure, phase compositions, microhardness and crystallographic texture of the HEA/CeO2 composites were investigated. It was demonstrated that CoCrFeMnNi HEA/CeO2 samples were successfully obtained by the LMD process. Meanwhile, small irregular shape oxides rich in Mn and Cr were observed in the HEA/ CeO2 composite. Rare earth element Ce was found to be evenly distributed throughout the sample. Heterogeneous dendritic microstructure with a long columnar grains oriented along the build direction was observed. The measured average microhardness is 181.72 ± 9.72 HV0.1.
关键词： Composite,CeO2,High entropy alloy,Laser metal deposition,Additive manufacturing,CoCrFeMnNi
更新于2025-09-23 15:21:01
-
A comparative study of laser metal deposited and forged Ti-6Al-4V alloy: Uniaxial mechanical response and vibration fatigue properties
摘要： This paper conducts a comparative study on mechanical properties of LMD and forged Ti-6Al-4V, focusing on uniaxial compression, tension and shear response with different strain rates, and vibration fatigue behaviors with 45–50 Hz in frequency. The micro-observation on initial microstructures and fractures explains the mechanism of lower uniaxial strength, shorter fatigue life, and larger dispersion in fatigue life and fracture position of LMD sample compared with the forged counterpart. Initial void defects within LMD sample tend to be stress-concentration zone, further initiating fatigue cracks. The columnar β grains leads to anisotropy of fatigue life and crack propagation for LMD sample.
关键词： Fracture analysis,Laser metal deposition,Vibration fatigue,Initial defect,Ti-6Al-4V
更新于2025-09-23 15:21:01
-
Effects of the Nozzle Tip Clogging and the Scanning Direction on the Deposition Process During Laser Metal Deposition of Alloy 718 Using a Four-Stream Discrete Nozzle
摘要： Depending on the configuration of the LMD system, the nozzle tilting is necessary to be able to manufacture parts with complex geometry. In these cases, the use of discrete coaxial nozzles is recommended. With this type of nozzle, the powder can clog the internal tips of the nozzle streams due to an inappropriate shape, size distribution, humidity or temperature conditions of the powder particles during the deposition process. This undesired effect can be an opportunity depending on the combination of the activated powder tips for coating complex surfaces when the geometry of the substrate acts as a barrier for the powder stream. This work presents for first time the effect of the scanning direction and the stream clogging on the deposition process in terms of powder efficiency, Material Deposition Rate (MDR) and clad geometry and dimensions, when Alloy 718 is deposited by LMD using a four-stream discrete coaxial nozzle.
关键词： Alloy 718,coatings,Laser metal deposition,geometrical characteristics,stream clogging,discrete nozzle
更新于2025-09-23 15:21:01
-
Analysis of helium used as protective gas in Laser Metal Deposition of Ti6Al4V highly reactive material
摘要： Laser Material Deposition (LMD) is an additive manufacturing near-net-shape process. Metal powder particles are molten by means of a laser heat source and added to a substrate creating geometries. This technology offers the possibility of generating coatings, repairing damaged high-added-value parts, and manufacturing components with complex 3D geometries. Many industrial sectors, including aerospace and die and mold industries, are interested in this process due to its capabilities and the wide range of materials that can be used with it. Previous works aimed to develop a protective gas module to be able to process highly reactive materials without the necessity of a complete inert atmosphere inside the machine. Additionally, the influence of a mixture of argon and helium on the LMD process for other non-highly reactive alloys was evaluated. Hence, the present work aims to broaden the understanding of how the combination of these two factors may affect the LMD process, combining these previous studies and evaluating the phenomenon for a highly reactive alloy like Ti6Al4V. The study involves the melt-pool temperature measurement and characterization of the deposited clads variating not only the composition of the protective gas but also the flow rates.
关键词： LMD,Ti6Al4V,Helium,Titanium,Shielding gas,protective atmosphere,He,Laser Metal Deposition,Argon,Ar
更新于2025-09-23 15:21:01