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[Laser Institute of America ICALEO? 2015: 34th International Congress on Laser Materials Processing, Laser Microprocessing and Nanomanufacturing - Atlanta, Georgia, USA (October 18–22, 2015)] International Congress on Applications of Lasers & Electro-Optics - Microstructural effects induced by laser shock peening for mitigation of stress corrosion cracking
摘要： Stress corrosion cracking is a phenomenon that can lead to rapid, sudden failure of metallic products. In this paper we examine the mechanisms of SCC mitigation of stainless steel and brass samples using laser shock peening (LSP). The behavior of hydrogen within the crystal lattice is one of the most dominant contributors to SCC, where uptake of hydrogen strains the lattice and increases its hardness. Cathodic charging of the metallic samples in 1M sulfuric acid was performed in order to accelerate hydrogen uptake. Non-treated samples underwent hardness increases of 28%, but LSP treated samples only increased in the range of 0 to 8%, indicative that LSP keeps hydrogen from permeating into the metal. Mechanical U-bends subjected and MgCl2 environments are analyzed, to determine changes in fracture morphology. Surface chemical effects are addressed via Kelvin Probe Force Microscopy, which is used for finding changes in the work function caused by LSP treatment. A finite element model of material deformation from U-bending was developed to analyze and compare the induced stresses. With LSP, there is a potential for overprocessing the samples, whereby negative effects refinement, to corrosion martensite formation) can arise. Detection of any martensite phases formed is performed using x-ray diffraction. We find LSP to be beneficial for stainless steel but does not improve brass’s SCC resistance. With our analysis methods we provide a further understanding of the process whereby LSP reduces subsequently highlight SCC for important implementation of the process.
关键词： Brass,Stainless steel,Hydrogen uptake,Stress corrosion cracking,Cathodic charging,Kelvin Probe Force Microscopy,Laser shock peening,Finite element model
更新于2025-09-23 15:21:01
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Filler metal distribution and processing stability in laser-arc hybrid welding of thick HSLA steel
摘要： Welds made by high power laser beam have deep and narrow geometry. Addition of filler wire by the arc source, forming the laser-arc hybrid welding (LAHW) process, is very important to obtain required mechanical properties. Distribution of molten wire throughout the entire weld depth is of concern since it tends to have low transportation ability to the root. Accurate identification of filler metal distribution is very challenging. Metal-cored wires can provide high density of non-metallic inclusions (NMIs) which are important for acicular ferrite nucleation. Accurate filler distribution can be recognized based on statistical characterization of NMIs in the weld. In the present study, it was found that the amount of filler metal decreased linearly towards the root. The filler metal tends to accumulate in the upper part of the weld and has a steep decrease at 45–55 % depth which also has wavy pattern based on longitudinal cuts. Substantial hardness variation in longitudinal direction was observed, where in the root values can reach > 300 HV. Excessive porosity was generated at 75 % depth due to unstable and turbulent melt flow based on morphology of prior austenite grains. The delicate balance of process parameters is important factor for both process stability and filler metal distribution.
关键词： Filler metal distribution,Microstructure,Thick steel,Non-metallic inclusions,High strength steel,Mechanical properties,Laser-arc hybrid welding
更新于2025-09-23 15:19:57
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Distortion and Dilution Behavior for Laser Metal Deposition onto Thin Sheet Metals
摘要： The combination of additive manufacturing and incremental sheet forming offers great flexibility in the manufacture of function-integrated parts. In this study, both processes were carried out by the same CNC machine. This offers the possibility to manufacture large-scale lightweight parts with smaller additive parts on it in one machine and clamping device. Additionally, the process combination can lead to a reduced energy and material consumption for small batch sizes. DC01 sheets are used as a substrate with two different initial conditions. The first condition is as delivered steel sheet and the second is an incrementally formed with a thickness of 0.5 mm. The additive manufacturing was conducted by laser metal deposition (LMD). The powder material is a stainless steel 316 L. A segmentation of the cladding surface was applied and the path strategy of the laser movement was varied simultaneously to analyse the warpage of the thin substrate. It is shown that there is a dependency between the build-up strategies and the melt pool temperature, the thermal distortion, the dilution and the size of the cladding area. A segmentation of the working surface causes a lower melt pool temperature and thermal distortion. The lower melt pool temperature also generates a reduced dilution zone.
关键词： Thermal distortion,Laser metal deposition,Incremental sheet forming,Stainless steel
更新于2025-09-23 15:19:57
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Examination of relationship between Urbach energy and open-circuit voltage deficit of flexible Cu(In,Ga)Se <sub/>2</sub> solar cell for its improved photovoltaic performance
摘要： Flexible Cu(In,Ga)Se2 (CIGSe) solar cells on stainless steel (SUS) substrates are developed. The contribution concentrates on the investigation of the correlation between Urbach energy (EU) and open-circuit voltage deficit (VOC,def). The several CIGSe solar cells on soda-lime glass and SUS substrates with various VOC,def values are fabricated through the variations of [Ga]/([Ga]+[In]) ratio (GGI), substrate temperature (TSUB) and Fe concentration of their CIGSe absorbers. The EU is determined based on external quantum efficiency in the long-wavelength edge. It is determined that the EU is influenced by the GGI, TSUB and Fe concentration. The EU is well consistent with the carrier lifetimes and can be an indicator of the CIGSe quality. In addition, the relationship between EU and VOC,def is obviously observed, where the decrease in the EU by 1 meV reduces the VOC,def by 8.6 mV. Through the optimizations of GGI and TSUB as well as the minimization of Fe concentration, the EU is obviously reduced, which implies the improvement of the CIGSe quality. Ultimately, the high η of 17.9% for the flexible CIGSe solar cell on SUS substrate is attained.
关键词： Cu(In,Ga)Se2,stainless steel substrate,TRPL carrier lifetime,Urbach energy,open-circuit voltage deficit
更新于2025-09-23 15:19:57
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Experimental investigation on Ytterbium fiber laser butt welding of Inconel 625 and Duplex stainless steel 2205 thin sheets
摘要： In this study, welding of Superalloy Inconel 625 and duplex stainless steel 2205 (DSS 2205) has been successfully performed through Ytterbium fiber laser at different heat inputs. With decreasing energy input, width of the weld bead narrowed and the mechanical properties of the joint improved. Characterization of the weld joint was carried out using Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS), X-Ray Diffraction (XRD), and micro-hardness testing. No solidification cracks or porosity was observed in the microstructure of the weld metal (WM). Cellular dendritic and columnar dendritic grains were main grain types observed in the weld metal. At heat input of 43 J/mm, inter-dendritic arms of the weld metal witnessed more segregation of Molybdenum and Niobium in comparison of welded samples at heat input of 21.5 J/mm. Carbides of Cr, Mo and Ni are formed in the weld joint interface as revealed by the XRD analysis. Tensile strength study reveals the maximum strength of 890 MPa when the heat supplied is low i.e. 21.5 J/mm. This strength value is more than that of the base metal (DSS 2205). The result obtained in terms of comprehensive structure-property correlation, recommends the effectiveness of laser beam welding for joining of the said dissimilar alloys.
关键词： Mechanical properties,Laser beam welding,Duplex stainless steel 2205,Microstructure,Inconel 625
更新于2025-09-23 15:19:57
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Experimental and Numerical Simulation on Laser welding of High Manganese TWIP980 Steel
摘要： In this paper, the numerical simulation of laser tailoring process for the 2mm thickness TWIP980 steel sheet is carried out using Simufact welding software. The results show that the center of the laser welding heat source is small, and temperature is high. The front of the weld pool has a drop-shaped profile and a funnel-shaped cross section. The simulated weld joint has a high degree of conformity comparing to the actual weld joint. As the heat input (line energy) increases, the peak temperature of the thermal cycle and the weldment width increase. The simulated results indicate that the residual stress of the weld joint perpendicular to the weld along the surface is greater than that along the weld direction, and are both greater than the residual stress perpendicular to the weld along the thickness direction. The residual stress generated by welding is mainly concentrated in the direction perpendicular to the weld seam. With the heat input increase, the deformation after welding increases. For the studied TWIP980 steel, the recommending laser tailored blank (LTB) weld parameters are: power 3kW and welding speed 3m/min, which is the optimum welding process in the practical welding. The guiding significance of the software for laser welding simulation of TWIP980 steel was verified.
关键词： numerical simulation,laser welding,residual stress,temperature field,TWIP980 steel
更新于2025-09-23 15:19:57
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Laser Heat Treatment of Ferrocarbon Powder Steel
摘要： The laser heat treatment of sintered ZhGr ferrocarbon powder steel with different porosity is considered. The microstructure and microhardness of the steel are determined, and the defects arising in laser treatment are studied.
关键词： microhardness,ferrocarbon steel,porosity,laser heat treatment,powder metallurgy,microstructure
更新于2025-09-23 15:19:57
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Enhancement of the surface properties of selective laser melted maraging steel by large pulsed electron-beam irradiation
摘要： The present work aimed to decrease the surface roughness of maraging steel (MS) by selective laser melting (SLM) using large pulsed electron-beam (LPEB) irradiation as a post-treatment. The MS samples were fabricated using different combinations of laser power, scanning speed, hatch distance, and build angle. The morphological features, surface roughness, phase content, and corrosion resistance of the MS samples in their as-fabricated (ASF) state were compared after LPEB irradiation. The ASF SLM-MS samples exhibit the presence of partially melted particles that spread over the entire surface and many cracks in both the longitudinal and transverse directions. A higher arithmetical mean height (Sa: 2-17 μm), large variations in Sa measured at various locations, and a strong dependence of Sa on build angle were also observed. Post-treatment by LPEB irradiation removed the partially melted particles, while reflow of the molten mass filled the cracks and voids and facilitated the formation of a uniform surface with a bright metallic finish. This has resulted in a significant decrease in Sa (0.50-4.50 μm) and a smaller variation in Sa measured at different locations. Body-centered cubic α-martensite was the predominant phase for the ASF SLM-MS samples, along with a small fraction face-centered cubic γ-austenite phase. After LPEB irradiation, the martensite was reverted to the austenite phase. The corrosion resistance of the LPEB-irradiated samples was moderately better than that of the ASF SLM-MS samples. The uniform surface morphology, removal of partially melted particles, absence of pores and cracks, decrease in Sa, and moderate improvement in corrosion resistance suggests that LPEB irradiation can be used as a post-treatment for SLM-MS samples.
关键词： corrosion resistance,large pulse electron beam irradiation,maraging steel,Selective laser melting,surface roughness
更新于2025-09-23 15:19:57
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Electrodeposition of hierarchical zinc oxide nanostructures on metal meshes as photoanodes for flexible dye-sensitized solar cells
摘要： Hierarchical zinc oxide (ZnO) nanorod arrays (ZNRAs) were fabricated on stainless steel meshes via a two-step electrodeposition approach as flexible dye-sensitized solar cells (DSSCs) photoanodes. The two-step electrodeposition was realized by deposition of primary ZNRAs followed by growth of secondary branched ZnO nanorods on the primary ZnO nanorods surfaces. The morphologies of ZNRAs and the photovoltaic performances of the assembled DSSCs with different deposition conditions of primary ZNRAs were compared in detail. After modulating electrodeposition conditions, the DSSC assembled with hierarchical ZNRAs obtained an optimum photovoltaic performance with power conversion efficiency of 1.81 %.
关键词： Electrodeposition,Zinc oxide,Stainless steel mesh,Dye-sensitized solar cells,Flexible photovoltaic devices
更新于2025-09-23 15:19:57
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The influence of a protective environment during direct laser deposition on the formation of structure and properties of steel F690W (09CrNi2MoCu)
摘要： The article presents the study of the direct laser deposition (DLD) process of cold-resistant steel 09CrNi2MoCu (F690W). As a result, many bainite transformation products are produced. The formation of a bainitic structure in the process of deposition is still little studied; in the process of the growth of the deposited wall, the microstructure undergoes a phase transformation. The work details the equipment for direct laser deposition, describes the main technological parameters of the regime, and studies the surface of the steel powder. Mechanical tests for impact toughness were carried out at a temperature of (cid:1)40 (cid:1)C, with different laser emission powers. The results are given using the initial powder, as well as used powder with a different mixing ratio, and the results are analyzed. As a result of the study, it was established that the fractional composition of the F620W alloy powder has a signi?cant effect on the mechanical characteristics of samples obtained by direct laser deposition. The effect of recycled powder on the mechanical properties of the samples obtained is given.
关键词： Direct laser deposition,Arctic,Bainite structures,Additive technology,Cold resistant steel,Direct metal deposition
更新于2025-09-23 15:19:57