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Non-dimensional process maps for normalized dilution limits in laser direct metal deposition
摘要： The quality and integrity of laser direct metal deposition (DMD) processes primarily depend on the substrate dilution and the nature of residual stresses in the deposited layer. An adequate amount of melting of the substrate is required to ensure the formation of sound metallurgical bond between the deposited layer and substrate. Insufficient melting and excessive dilution may lead to adverse effects. Furthermore, the dilution also controls the location of the melt front in substrate where maximum tensile residual stresses occur. The presence of tensile residual stresses in the deposited layer may be detrimental to service life, especially, for components repaired using DMD. These challenges can be overcome by predicting and controlling the dilution and the nature of residual stress as a function of process parameters. To model the direct metal deposition process, a 3D coupled metallo-thermomechanical finite element model is employed to predict the temperature and the residual stress due to thermomechanical interactions and metallurgical transformations and the substrate dilution. Non-dimensional process parameters affecting the dilution in laser DMD have been identified using Buckingham-Π theorem. The metallo-thermomechanical model is used to develop empirical relationships via regression to correlate the dimensionless process parameters with the dilution. These correlations are employed in developing the isopleths in the form of process maps, which could predict regions of inadequate fusion and excessive dilution (unduly large substrate melting). It may be noted that the limiting value of dilution corresponds to the condition where the entire deposited layer (cladding) is under compressive residual stresses. Any dilution higher than this will result in excess substrate melting which is undesirable. The limiting values of normalized dilution are estimated to be 1 and ~1.3 corresponding to complete deposit-substrate fusion and presence of entirely compressive residual stress in deposition, respectively. These process maps are designed to provide a theoretical framework for understanding the influence of process parameters and provide informed decisions on the selection of appropriate process parameters for ensuring the quality and integrity of the deposition.
关键词： Laser cladding,residual stress,metallo-thermomechanical finite element model,process maps,dilution,non-dimensional parameters
更新于2025-09-12 10:27:22
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Laser cladding in-situ nano-submicron TiC reinforced ultrafine- grained Fe-based composite layers on 42CrMo steel
摘要： In-situ nano-submicron TiC reinforced ultrafine-grained Fe-based cladding layers were prepared by laser cladding gradient particle sizes of ferrotitanium, graphite, and iron powder on the surface of 42CrMo steel. Microstructures and corrosion resistance were analyzed using X-ray diffraction, scanning electron microscope, and an electrochemical workstation. Results showed that the average particle size of the in-situ TiC was 0.25 μm, and ranged from 0.04 μm to 1.10 μm, with 11.0 % being on the nano scale. The microstructure of the cladding layer was lath martensite, and the average grain size of the cladding layer matrix was 4.08 μm, reaching the ultrafine-grained scale. The average hardness of the cladding layer was approximately 720 HV0.2, which was 425 HV0.2 higher than that of the 42CrMo steel. The corrosion current density of the cladding layer was more than two times lower than that of the 42CrMo steel.
关键词： nano-submicron,ultrafine-grained,TiC,laser cladding
更新于2025-09-12 10:27:22
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Wear Tribo-Performances of Laser Cladding Colmonoy-6 and Stellite-6 Micron Layers on Stainless Steel 304 Using Yb:YAG Disk Laser
摘要： Stainless steel material has been widely used in aeronautical, chemical and nuclear industries due to good corrosion resistance. However, the material has less hardness and wear resistance. In this study, two various depositions namely Colmonoy-6 and Stellite-6 have produced on 304 Stainless steel. Besides, the coating was examined to reveal their metallurgical, mechanical and tribological properties. In addition, wear mechanism, wear debris and roughness averages were studied. The outcomes indicate that both coatings show with dendrite structure due to rapid cooling rates. Hardness of the clad surface has improved than substrate material. The results of friction coefficient of specimen with Colmonoy-6 is lower than that of specimens Stellite-6 and substrate. Also, wear resistance of Colmonoy-6 has increased 49 times than substrate sample, which reveals that Colmonoy-6 laser cladding plays role on wear resistance. Adhesive and abrasive are the major wear mechanisms in the present study.
关键词： Wear debris,Microstructure,Stainless steel 304,Roughness,Wear performance,XRD,Laser cladding,Hardness
更新于2025-09-12 10:27:22
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Cr12MoV Die Repair Experiment Based on Laser Cladding with Wire
摘要： In this paper, SKD11 steel wire has been deposited on Cr12MoV plate using Nd: YAG pulsed laser for repairing the die surface damage. The effects of laser power, wire feeding speed, scanning speed and surface roughness on clad geometry have been studied with OM and LSCM. hardness distribution of the cladding layer is also obtained by microhardness tester. Experiment results indicate that the surface roughness is important for clad characteristics due to the light trapping effect. With the increases of roughness, the laser absorption ratio can be raised, both the clad depth and the dilution rate increase, the height decreases. The essence of influence mechanism is effective body energy Ev and specific filling rate ω, and can be used as critical process factors. When Ev is 80~100 J/mm3 and ω is 1~3, a flat cladding layer can be obtained with low dilution, less fusion defects and high hardness.
关键词： laser cladding with wire,clad geometry,hardness,Cr12MoV,surface roughness
更新于2025-09-12 10:27:22
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Femtosecond Laser Written Depressed-Cladding Waveguide 2 × 2, 1 × 2 and 3 × 3 Directional Couplers in Tm3+:YAG Crystal
摘要： Ion-doped crystal-based compact devices capable of beam splitting and coupling are enthralling for a broad range of classical and quantum integrated photonics applications. In this work, we report on the fabrication of depressed-cladding waveguide 2D 2×2, 1×2 and 3D 3×3 directional couplers in Tm3+:YAG crystal by femtosecond laser writing. The performances of the couplers are characterized at 810 nm, showing single-mode guidance, polarization independence, ?nely matched splitting ratios. These results open up new opportunities in the bene?cial fabrication of 3D circuits and devices in crystals.
关键词： crystal,femtosecond laser writing,directional coupler,depressed-cladding waveguide,integrated photonics,yttrium aluminum garnet,quantum memory
更新于2025-09-12 10:27:22
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Characterization and tribological evaluation of NiCrMoNb and NiCrBSiC laser cladding on near-α titanium alloy
摘要： In the present study, two different types of coatings such as NiCrMoNb and NiCrBSiC were produced on titanium alloy using a high power Yb:YAG disk laser. Then the coatings were analysed to expose their phase characterization, microstructure and hardness using X-ray diffraction analysis (XRD), energy-dispersive spectroscopy (EDS), scanning electron microscopy (SEM), optical microscopy (OM) and Vickers microhardness machine (HV). Further, tribotest was performed through ball-on-plate machine to analyse the wear properties of coatings. In addition, worn surfaces of cladding and surface roughness were examined using FE-SEM and whitelight interferometer, respectively. The results showed that the both NiCrMoNb and NiCrBSiC cladding exhibited a dendrite homogeneous structure due to higher cooling rates. XRD results indicating that the solid solution of γ-Ni was mixed with chromium, boride, silicon and formed the structure of interdendritic eutectics on cladding region. Microhardness of the clad layer has remarkably been increased than substrate. The results of friction coefficient of specimen with NiCrBSiC are lower than that of specimens NiCrMoNb clad and substrate. Also, the wear resistance of NiCrBSiC clad has been increased than NiCrMoNb clad and substrate sample, which reveals that NiCrBSiC laser cladding plays a major role on wear resistance. The microstructures of NiCrMoNb and NiCrBSiC cladding layer are composed of Ni-rich austenitic, Cr, Mo, Nb and carbide, borides, respectively. The analysed wear track indicates that adhesion and abrasion was a major wear mechanism. The NiCrSiBC cladded worn-out surfaces exhibited reduction in surface roughness than NiCrMoNb clad and substrate.
关键词： NiCrBSiC,Cladding,Microstructure,Titanium alloy,Surface roughness,Wear mechanism,NiCrMoNb
更新于2025-09-12 10:27:22
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Investigation of Crystallization Process of a Single Crystal Nickel-Based Alloy during the Laser Multilayer Cladding
摘要： The article shows the results of multilayer laser cladding of heat-resistant single crystal nickel-based alloy ZhS32-VI (CSMX-4 analogue). The influence of the main technological parameters on geometry and microstructure formation of deposited beads was investigated. Based on obtained dependencies, the regression equations are compiled for describing the shape of bead and the ratio of directional and equiaxial crystallized sections. The obtained dependencies of regime parameters nomination allow restoring the gas-turbine blades by the method of laser cladding.
关键词： gas-turbine blades,heat-resistant nickel-based alloys,laser cladding,crystallization,single crystal nickel-based alloys
更新于2025-09-12 10:27:22
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Liquid crystal tunable claddings for polymer integrated optical waveguides
摘要： Optical waveguides in photonic integrated circuits are traditionally passive elements merely carrying optical signals from one point to another. These elements could contribute to the integrated circuit functionality if they were modulated either by variations of the core optical properties, or by using tunable claddings. In this work, the use of liquid crystals as electro-optically active claddings for driving integrated waveguides has been explored. Tunable waveguides have been modeled and fabricated using polymers. Optical functions such as variable coupling and optical switching have been demonstrated.
关键词： tunable cladding,photonic integrated circuit,liquid crystal,polymer waveguide,organic waveguide
更新于2025-09-12 10:27:22
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Modeling and optimization for laser cladding via multi-objective quantum-behaved particle swarm optimization algorithm
摘要： The process parameters of laser cladding have significant effects on the quality of the laser clad coating. Generally, optimizing one property usual lead to deterioration in some other performances. In this study, the influence of key parameters to preparing the CoCr1.5FeNiNb0.5 coating, namely laser beam power, scanning speed and defocus, on the dilution and residual stress were systematically researched. The polynomial model for the parameters on dilution and residual stress was designed by response surface methodology and the effect of each parameter on the responses was investigated. Then the quadratic models were used as the constraint functions and multi-objective quantum-behaved particle swarm optimization was applied to find the minimum dilution and residual stress. At last, the optimal process parameters were predicted by this algorithm and the high entropy alloy coating was manufactured. The CoCr1.5FeNiNb0.5 HEA coating consisted of FCC and Laves phase.
关键词： Dilution,Residual stress,Response surface methodology,Laser cladding,Multi-objective
更新于2025-09-12 10:27:22
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Aluminium Matrix Composites Produced by Laser Based Additive Manufacturing
摘要： 3D laser metal deposition (LMD) based on the laser cladding is an established technique for additive manufacturing tasks. Also the laser cladding is a well-known technique to produce aluminum matrix composites reinforced by Si particles. High cooling rates typical for laser treatment enable to eliminate coarse Si particles formation which is a substantial disadvantage of in-situ Al-Si composites produced by traditional manufacturing processes like casting. The coarse Si particles formation reduces Al-Si composites mechanical properties. Extremely non-equilibrium solidification conditions typical for micro LMD process allow to obtain a further structure refinement and its mechanical properties improvement. In this paper the in-situ Al-Si composites produced by micro LMD process with different parameters sets were investigated by fine structure X-ray analysis. The structure and phase composition of in-situ Al-Si composites were described. The influence of cladding parameters on Al-Si composites structure was investigated.
关键词： MMC,aluminium matrix composites,Laser micro cladding,thin-wall parts,fine structure,additive manufacturing,aluminium alloys,X-ray analysis,thin wall
更新于2025-09-12 10:27:22