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Evaluation of fluences and surface characteristics in laser polishing SKD 11 tool steel
摘要： In this paper, a continuous-wave laser beam from a multimode fiber laser was applied to study the polishing effect. Three kinds of surface morphologies were acquired by fast-speed (FS) & lower-speed (LS) wire electrical discharge machining (EDM), milling processing methods on SKD11 tool steel. Then influence of laser fluence on the polished surface characteristics was analyzed. The results showed that surface roughness parameters (Ra, Rz, Rt, and Sa) can be significantly affected by this effect. With laser fluence increasing, the polished surface underwent a comprehensive topographical evolution from superficial surface melting to surface over-melting. The improvements by FS-EDM, LS-EDM, and milling in roughness were 86.83%, 90.70% and 86.07%, respectively. The corresponding laser fluences were 14.26 J/mm2, 12.73 J/mm2 and 13.55 J/mm2, indicating that LS-EDM tool steel surface has the best polishing effect. The comparative statistical results of the bearing area curve, bidirectional reflectance distribution function, and power spectral density from the LS-EDM surfaces showed the best polishing results. In addition, all the pre-prepared surfaces could be polished to Ra < 0.5 μm using high polishing velocities. These findings also signified that laser beam with top-hat distribution has a great potential for high-efficiency polishing of tool steel surfaces.
关键词： Power spectral density,Surface morphology,Bearing area curve,Fluence,Laser polishing,Tool steel
更新于2025-11-28 14:24:20
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Laser polishing of additively manufactured Ti-6Al-4V: Microstructure evolution and material properties
摘要： Laser polishing of metals consists of irradiating the part’s surface with a laser beam, thus generating a molten layer that is redistributed and resolidified to create a surface with reduced roughness. However, the process is also characterized by an instantaneous formation of heat-affected zones with consequent microstructural changes that influence the mechanical properties. In order to understand the microstructural evolution during laser polishing of Ti-6Al-4V laser-based powder bed fusion samples, a thermal model is applied in the current study to predict the dimensions of the melted zones and the heat-affected areas. Furthermore, the results obtained through simulations are discussed and compared to the experimental data, thereby establishing the validity of the process models. Finally, the experimental studies also include the evaluation of material hardness and residual stresses after laser polishing.
关键词： laser polishing,thermal model,material properties,additive manufacturing,microstructure evolution
更新于2025-09-23 15:21:01
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Influence of laser polishing on surface roughness and microstructural properties of the remelted surface boundary layer of tool steel H11
摘要： This work investigates the influence of multi-step laser polishing on microstructural properties of the remelted surface layer of tool steel H11. Four different laser polishing process parameter sets were selected that lead to a significant reduction in roughness. In a sequential process using continuous and pulsed laser radiation (Nd:YAG) a significant reduction of surface roughness was achieved on an initially annealed H11 sample. The remelted layers were analyzed using roughness measurements, white light interferometry, X-ray diffractometry, electron backscatter diffraction, glow discharge emission spectroscopy, and nanoindentation hardness measurements. Laser polishing leads to a grain refinement and a significant increase in hardness. A surface roughness of Ra 50nm was achieved in an Argon process atmosphere with an additional 6vol% CO2. In particular the carbon concentration was more than halved within the remelted layer. The lower carbon concentration is correlated with a decreased maximal surface hardness down to 366HV. High residual tensile stresses of up to 926MPa can be introduced by laser polishing. Overall, high temperature gradients and, in particular, decarburization due to carbon diffusion processes were identified to be the major driving force for significant changes in surface micro-roughness and microstructural properties.
关键词： AISI H11,micro hardness,laser polishing,decarburization,surface roughness,martensite formation
更新于2025-09-23 15:21:01
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Laser surface re-melting of additive manufactured samples with a line focused beam
摘要： The laser polishing mechanism is based on the fusion of a micro layer of material due to the action of the high temperature laser beam. Laser polishing, also known as laser surface remelting, involves melting a thin layer of the substrate, with surface tension causing the material to flow from peaks to valleys. In laser polishing, the material is not removed; rather it is relocated as a molten pool. The laser beam with sufficient energy density is first allowed to quickly fuse a layer on the substrate surface of microscopic thickness. Accordingly, the peaks of the asperities on the substrate surface are fused. Owing to the fluidity of this molten metal, it easily flows into the adjacent valleys of the asperities on the surface. The same molten layer is then allowed to re-solidify so that solidified layer remains adhered to the substrate surface. This, in turn, diminishes the peaks and valleys of the asperities, which ultimately results in a smoother surface. Since surface roughness is one major limitation of additive manufacturing components, so this article makes an attempt to address the roughness of such components. The capability of laser polishing (or laser surface remelting) in reducing surface roughness is explored for various beam power and scan speed. The better set of parameters for this purpose are presented. A final surface roughness in the range of 1.0–1.1 lm is obtained for three different set of parameters. 85% reduction in surface roughness due to laser polishing is also observed.
关键词： Cylindrical lens,Laser polishing,Surface roughness,Additive manufacturing,Laser surface remelting
更新于2025-09-23 15:19:57
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Top-hat and Gaussian laser beam smoothing of ground fused silica surface
摘要： Laser smoothing is a promising technique for processing optical glass due non-contact characteristics and easy-adaptability to non-spherical surfaces. The smoothing effects of CO2 laser of top-hat and Gaussian intensity on ground fused silica surfaces were examined in the work. The results show that ground surface with surface micro-roughness of 500 nm (RMS) can be smoothed to < 0.5 nm (RMS) with both intensity profiles. Best surface roughness rises with increasing power density of laser and therefore lower power density combined with slow scanning speed is favored to improve surface quality. Numerical model was established to investigate thermal and hydrodynamic transient process to elucidate the underlying mechanism. Simulations show that smoothing process takes place at the same time as the temperature rises due to ever-decreasing viscosity of fused silica. Beam shaping is able to reduce peak power density of high power processing laser and smoothing efficiency might be increased without the loss of the processed quality of glass.
关键词： Laser smoothing,Roughness,Top-hat beam,Gaussian beam,Fused silica,Laser polishing
更新于2025-09-23 15:19:57
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Investigation of Laser Polishing of Four Selective Laser Melting Alloy Samples
摘要： Selective laser melting (SLM) is a layer by layer process of melting and solidifying of metal powders. The surface quality of the previous layer directly affects the uniformity of the next layer. If the surface roughness value of the previous layer is large, there is the possibility of not being able to complete the layering process such that the entire process has to be abandoned. At least, it may result in long term durability problem and the inhomogeneity, may even make the processed structure not be able to be predicted. In the present study, the ability of a fiber laser to in-situ polish the rough surfaces of four typical additive-manufactured alloys, namely, Ti6Al4V, AlSi10Mg, 316L and IN718 was demonstrated. The results revealed that the surface roughness of the as-received alloys could be reduced to about 3 μm through the application of the laser-polishing process, and the initial surfaces had roughness values of 8.80–16.64 μm. Meanwhile, for a given energy density, a higher laser power produced a laser-polishing effect that was often more obvious, with the surface roughness decreasing with an increase in the laser power. Further, the polishing strategy will be optimized by simulation in our following study.
关键词： laser polishing,additive manufacturing,selective laser melting,typical alloys,surface roughness
更新于2025-09-19 17:13:59
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Laser polishing of tool steel using a continuous-wave laser assisted by a steady magnetic field
摘要： Continuous-wave (CW) lasers are widely used in laser polishing, but with CW laser polishing, it is difficult to reduce the surface roughness to 0.2 μm from an original value exceeding 1.0 μm. The aim of this study is to develop an innovative method of laser polishing assisted by a steady magnetic field to overcome that bottleneck and produce smoother surfaces. Two experiments confirm the hypothesis that the molten pool overflows during melting peaks to flow into valleys in CW laser polishing, resulting in secondary roughness that causes the aforementioned quality bottleneck. To either reduce or eliminate this secondary roughness, a steady magnetic field is used during CW laser polishing to suppress the overflow of the molten pool. A three-dimensional surface profiler, a scanning electron microscope, and a nanometer indentation tester are used to characterize and analyze the microstructure and properties of the materials. The experimental results show that the Lorentz force due to the steady magnetic field plays an important suppression role in reducing the secondary roughness.
关键词： laser polishing,steady magnetic field,Lorentz force,molten pool overflow,continuous-wave laser,surface roughness
更新于2025-09-19 17:13:59
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Laser Polishing of Ti6Al4V Fabricated by Selective Laser Melting
摘要： Selective laser melting (SLM) is emerging as a promising 3D printing method for orthopedic and dental applications. However, SLM-based Ti6Al4V components frequently exhibit high roughness values and partial surface defects. Laser polishing (LP) is a newly developed technology to improve the surface quality of metals. In this research, LP is applied to improve the surface ?nish of components. The results show that the laser beam can neatly ablate the aggregates of metallic globules and repair cracks and pores on the surface, resulting in a smooth surface with nanocomposites. Overall, the results indicate that using LP optimizes surface morphology to favor fatigue behavior and osteoblastic di?erentiation. These ?ndings provide foundational data to improve the surface roughness of a laser-polished implant and pave the way for optimized mechanical behavior and biocompatibility via the laser process.
关键词： laser polishing,additive manufacturing,biocompatibility,mechanical properties,surface roughness
更新于2025-09-19 17:13:59
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Thermodynamics analysis and rapid solidification of laser polished Inconel 718 by selective laser melting
摘要： This paper presents thermodynamics analysis and rapid solidi?cation of laser polishing technology for selective laser melting (SLM) Inconel 718 superalloy. Signi?cant porosity reduction has been examined in the laser polished layer, where the surface porosity is reduced by 65.7% compared with that of the as-fabricated SLM surface. The results show that the temperature in the polished zone is over 1683 K, and the cooling rate is approximately up to 2.46 × 106 K/s. Besides, the polished layer consists of equiaxed grain and columnar grain with average grain size of 10 ± 2.4 μm and 5 ± 1.2 μm, respectively, and tiny cell grains with average size of 3.5 μm in the heat-a?ected zone (HAZ). Moreover, the transmission electron microscope (TEM) results show that the orientation relationship (OR) between the γ matrix and Laves phase is found to be Burgers OR [0 1 1] ‖[0 1 1ˉ 2] Laves on the as-received layer and [1ˉ 1 1] ‖[1 2ˉ 1 3ˉ] Laves on the polished layer.
关键词： Inconel 718 superalloy,Microstructural evolution,Crystallographic orientation,Selective laser melting,Laser polishing
更新于2025-09-16 10:30:52
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Study on processing characteristics and mechanisms of thermally assisted laser materials processing
摘要： Nanosecond pulsed lasers have been widely applied to interact with and characterize many di?erent materials, and industrial users are exploring more avenues for various application processes. For the purpose of achieving broader application, the current challenge is to achieve a high processing e?ciency for laser materials processing. In this study, thermally assisted laser materials processing (TALMP), which introduces heat from an external source to increase the workpiece material's temperature and make it easier to carry out ablation or modi?cation, was developed and investigated. Moreover, to investigate the materials processing characteristics and mechanisms of TALMP, practical applications using TALMP, including surface ablation on WC-Co, and surface polishing on additive manufactured Ti-6Al-4V, were carried out. The results showed that TALMP can be successfully applied to various materials by di?erent laser materials processing applications. Due to the workpiece material's high temperature and heat content, the coupling between laser and target materials can be enhanced; thus, physical ablation and modi?cation for laser surface ablation can be achieved e?ectively. However, with a high o?set temperature, a little decrease of ablation accuracy and quality could occur, and a two-step approach is proposed to eliminate this unwanted e?ect. Moreover, this strategy is proven to be able to achieve the desired surface ablation with high e?ciency and high-quality surfaces. For thermally assisted surface polishing, due to higher temperature ?eld with long duration, a smoother and ?atter polished surface can be obtained more easily. The experimental results proved the superiority and versatility of TALMP.
关键词： Laser polishing,Thermally assisted,Laser materials processing,Laser ablation
更新于2025-09-12 10:27:22