High build rates in laser-directed energy deposition (L-DED) often lead to defects and microstructural anisotropy, resulting in compromised mechanical performance. This study proposes a novel remelting-assisted high-rate deposition (RHD) strategy, where a dedicated corrective laser remelting pass is applied after each deposited layer to refine and homogenize the microstructure. L-DED experiments were conducted using stainless steel (SS316L) powder to compare the RHD strategy with standard deposition (SD, using a conventional 7g/min powder feed rate) and high-rate deposition (HD, employing an aggressive 25g/min powder feed rate). Both SD and HD produce coarse, columnar grains aligned with the build direction, resulting in significant yield-strength anisotropy. In contrast, remelting-assisted high-rate deposition (RHD) samples exhibit a 38% increase in yield strength and a 15% increase in ultimate tensile strength compared to the high-rate deposition (HD) condition, accompanied by a 26% reduction in ductility. Mechanical anisotropy was significantly reduced, with yield strength variation across orientations decreasing by 57%. Fatigue performance was also enhanced, with remelting-assisted high-rate deposition (RHD) samples sustaining 13% higher stress amplitudes in low-cycle fatigue (LCF) and exhibiting a nearly four-fold increase in high-cycle fatigue (HCF) life compared to HD. Fundamentally, in-situ remelting modifies solidification pathways by locally resetting thermal gradients, interrupting epitaxial columnar growth, and promoting microstructural refinement. These benefits are achieved at an effective build rate of 10.5g/min, corresponding to a 50% reduction in build time compared to standard deposition (SD). Although the additional remelting passes reduce the effective build rate relative to high-rate deposition (HD, 17.5g/min), this controlled trade-off enables precise process–structure control over grain morphology, crystallographic texture, and defect populations during rapid builds. While HD alone leads to degraded mechanical performance, the integration of in-situ remelting not only restores but consistently surpasses the properties achieved under SD. Ultimately, this approach provides a scalable pathway for producing high-performance L-DED components that balance high productivity with superior mechanical integrity, including enhanced strength and fatigue resistance.

Abstract Wires with small diameters (0.1 mm–2 mm) often retain their initial curvature when uncoiled from a spool due to plastic deformation during the winding process. A wire straightening mechanism is required in various applications, such as wire laser-directed energy deposition (WLDED) and fabrication of microtools for the biomedical and semiconductor industries. In WLDED, the uncoiled wires of smaller diameters often retain residual bends and deformations, leading to feeding inconsistencies and affecting the quality of the final build. While commercial wire straighteners are effective for thicker wires, they are not adequately suited for fine wires used in WLDED. To overcome this challenge, a novel wire straightening mechanism has been developed and critically analyzed. The proposed design employs a multistage, three-point bending roller mechanism to efficiently straighten wires of varying diameters, materials, and initial curvatures. A mathematical model has been formulated to account for the initial curvature and material spring-back, enabling the prediction of the final wire shape in a three-roller bending process. The model predicts that the optimal curvature correction occurs at a certain roller actuation, which bends the wire at a particular curvature. The model identifies the number of bending stages required for curvature correction and the effect of the initial curvature on the bending process. For straightening a 1.2 mm SS 304 wire with an initial curvature of 350 mm to a final curvature of 14,359 mm, the model predicts a two-stage bending operation. The actuations in the first and second stages are 0.616 mm and 0.545 mm, respectively. For a 1.2 mm Al 4043 wire with an initial curvature of 170 mm, the model suggested a three-stage bending operation with a final radius of curvature of 13,342 mm. The model predictions and the measured values of the final curvature are in good agreement, with prediction errors ranging between 0.17% and 3.1%.

Laser cleaning is one of the most efficient and environment-friendly rust cleaning methods. The removal of the corrosion layer from steel surfaces by nanosecond pulsed lasers usually causes discolouration of the surface. By proper selection of laser parameters, this discolouration can be avoided without compromising the material removal rate. In this work, a study on the treatment combination of laser power, scan speed, pulse repetition rate, and hatch distance on the colour of the laser-cleaned surface and the material removal rate is conducted via response surface methodology using a central composite design. The factors and interactions that significantly affect the response were identified by ANOVA. The model was experimentally validated and the parameter combination that gives the highest material removal rates with a shiny surface was identified with ∼ 90 ^3 /s to 0.4 mm ^3 /s in the current range of parameters. The maximum material removal is observed to be at laser power between 7.5 - 10 W and hatch distance between 45-50 m when the scan speed is 875 mm/s and PRR is 50 kHz. However, the feasible region that can create a surface with the same metallic colour as a polished steel surface is extremely narrow when compared to the full range of the parameters used in the study.

High-speed electrical drives have become a key research focus due to their high power density and reliability. The advanced design of high-speed laminated rotor induction machine (HS-LRIM) introduces unique challenges. HS-LRIM is designed to withstand the high centrifugal forces and to deliver a torque of 40mN center dot m at 100 000 rpm, for high-speed micromachining application. A high amplitude torque oscillation with a low frequency is observed during the steady-state operation of the motor. A catastrophic shaft failure can be caused by torsional vibrations produced by torque oscillations. A novel design solution to address the problem of low frequency torque oscillation encountered in HS-LRIM, without violating the stress limits of the material is proposed in this article. The electromagnetic performance of the high-speed motor is analysed using ANSYS Maxwell 3D and the stress analysis of the rotor structure is performed in ANSYS Workbench.

Additive Manufacturing (AM) processes offer new routes for remanufacturing and restoration of worn components. Its special characteristics allow for the combination of materials with various properties and surface functionalization. Metal powder-based Laser Directed Energy Deposition (LDED) technique frequently fails to provide surface and dimensional quality, necessitating post-processing procedures. The present study assesses the viability and performance of conventional machining of CPM 9V crucible steel used for restoration of cylindrical H13 tool steel substrate through LDED process. In this study, hard turning was employed for finishing of ultra-hard CPM 9V deposit to study the effect of turning parameters i.e. cutting speed, depth of cut, and feed rate on cutting forces and surface roughness. The chip morphology and microstructure through EBSD have also been observed during the turning of hard CPM 9V. The experimental observation showed that in hard turning, with increasing cutting speed tangential force was reduced by 14% and radial force by 32%. Higher feed rates from 0.05 mm/rev to 0.15 mm/rev increase the tangential force by 43%, and decrease radial force by 22%, due to significant ploughing forces at lower uncut chip thicknesses affecting radial forces. The depth of cut significantly impacts all forces. Surface roughness was influenced mostly by cutting speed. In addition to this, the microhardness of the machined surface is higher (similar to 830.6 HV) in comparison to the deposited surface due to the work hardening. The microstructure showed the presence of carbides in the material matrix. It also presented that the machined surface has finer grains in comparison to the deposited clad grains resulting in deformation-induced hardness. Thus, this work has demonstrated the capability of hard turning in finishing the ultra-hard deposits obtained from LDED-based die repair. (c) 2025 The Authors. Published by ELSEVIER Ltd. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0)

Wire laser-directed energy deposition (WLDED) is a specially designed wire deposition process using a high-intensity laser beam as a source for the fabrication of bulk and free-form components. In this process, a laser beam strikes the substrate, creating the melt pool simultaneously; the wire is fed, which melts and integrates with the substrate. This process finds wide applications in biomedical, aerospace, marine, energy, and automotive sectors for component development and repair. WLDED is classified into two subparts: lateral feeding and coaxial WLDED. Coaxial WLDED is highly flexible for free-form deposition with uniform energy distribution across the deposits, diminishing microstructural, geometrical, and mechanical defects. Despite the listed advantages, defects like stubbing, burning, and dripping are challenging to avoid owing to the wire feed variability. Therefore, this research focuses on developing an autonomous, flexible, and state-of-the-art wire feeding setup and its integration with a coaxial wire laser deposition head. In addition, this work also focuses on deposition characterization, defect determination, and defect mitigation. The wire feeder setup is developed in-house, utilizing a highly optimized and stable roller engagement mechanism. To validate the component fabrication, single track deposition of AISI 304 stainless steel wire (1.2 mm diameter) on SS304 has been carried out at varying laser power (1200 W to 2000 W with the increment of 400 W) and scan speed (16 mm/s to 20 mm/s with the increment of 2 mm/s). The geometrical analysis at varying parameters is conducted by tracking the variation in deposition width, deposition height, dilution depth, contact angle, and deposit area. The dilution depth, substrate area, dilution %, and deposition width increase and decrease with laser power and scan speed, respectively. Acute contact angle (< 90°) values are obtained for all deposition parameters. Dilution %, dilution depth, and substrate area increases with increase in laser energy density due to higher laser energy reaching the substrate. Interestingly, stubbing, dripping, and burning are tracked by abnormal variations in deposition height, deposition width, and deposition area at extreme laser powers of 1200 W-2000 W and scan speed of 20 mm/s-16 mm/s. Therefore, the detrimental defects can be avoided by operating at medium scanning speed and laser power. All these results indicate successful integration of in-house developed coaxial WLDED setup with sound deposits. Microstructure variation obtained using electron backscattered diffraction (EBSD) results depicting directional solidification of columnar grain for all process parameters. Grain structure variation shows fine to coarse columnar grains transition from low to high energy density due to reduction in cooling rate. The linear energy density has insignificant effects on the microhardness value of the deposits. A small increase in microhardness (192.5 HV to 211.1 HV) is observed if laser energy density is reduced (111 J/mm to 66.7 J/mm). However, due to fine and twined equiaxed microstructure, the substrate displayed higher microhardness (260 ± 10 HV) than the deposits (190 ± 20 HV). Geometrical, microstructural, and microhardness results show 1600 W and 18 mm/s as the best-suited deposition parameter. The most exciting part of this work is that significantly fewer defects than earlier presented works have been obtained. Hence, we successfully integrated an in-house developed highly flexible wire feeding setup with a coaxial wire deposition head capable of producing sound deposits for the required applications. In addition, we also detected and listed the conditions of the defect’s formation.

This paper investigates the different material removal mechanisms that occur during quasi-continuous wave (QCW) fiber laser drilling using millisecond pulses on stainless steel 304 samples and studies their effect on hole quality. A high-speed imaging camera is integrated with an in situ laser setup to capture the material removal during the laser drilling process. Based on high-speed camera images, four different material removal mechanisms were observed, which include vaporization, melt-expulsion at the hole entrance, melt-ejection at the hole exit, and explosive boiling. Vaporization occurs at all fluences beyond a certain threshold and is followed by melt-expulsion after a particular laser fluence value, leading to material deposition at the periphery of the hole entrance. Explosive boiling occurs at higher fluences beyond a certain threshold, resulting in material removal in the form of vapor and liquid droplets. Besides, the high pressure involved in explosive boiling also causes melt-ejection from the hole's exit, leading to the formation of a through hole. Furthermore, it is observed that an assist gas plays a crucial role in effectively displacing the molten material, thus generating a uniform and through hole. This sequential evolution of mechanisms offers valuable insights into delineating the roles of each mechanism and developing process maps for the dimensions and quality of mu-holes produced.

Laser-directed energy deposition (LDED) is a promising technique for in situ alloying and multi-material deposition, with challenges related to powder catchment efficiency (PCE), microstructural, and mechanical properties variation, particularly during premix powder deposition. Therefore, this study investigates the influence of premix powder size on PCE, microstructure, and microhardness in the LDED of TiNiCu ternary alloy. Fine (Cu: 60 mu m-Ni: 60 mu m) and coarse (Cu: 150 mu m-Ni: 60 mu m) premixes are deposited on Ti substrates at various laser powers. The fine premix exhibits higher laser scattering, resulting in a wider melt pool formation compared to the coarse premix deposits. This results in significantly improved PCE and a larger deposition area for fine premix deposition. The fine premix deposition width is 30% higher than the coarse premix deposits at lower and medium laser power. However, the deposition width of coarse and fine premix deposits overlaps at higher laser power. Fine premix deposits (Ti-max: 28 wt%) contain lower Ti content than coarse premix (Ti-max: 42 wt%) but higher Cu (max: 51 wt%) and Ni (max: 43 wt%) content owing to enhanced PCE. As laser power increases, the coarse premix deposit microstructure changes from columnar to dendritic, while the fine premix deposit shows equiaxed to coarse columnar grain transformation. The coarse premix depicts Ti2CuNi and NiTi-B2 phases formation. In contrast, the fine premix deposits display a CuNi solid solution at lower laser power and a CuNiTi ternary phase with Cu segregation at higher laser powers. Microhardness in the fine premix deposits is 24%-29% lower than coarse premix deposits due to Cu segregation and phase evolution. Despite copper segregation, the hardness of the fine premix deposits remains at least 1.5 times higher than the substrate, primarily due to solid solution strengthening and the hard ternary phase. This work demonstrates that fine premixing enhances PCE, and by controlling powder size, both the mechanical and microstructural properties of the alloy can be tailored for specific applications, such as ternary TiNiCu alloy engineering for titanium surface functionalization and corrosion resistance. (c) 2025 The Authors. Published by ELSEVIER Ltd. This is an open access article under the CC BY-NC-ND license(http://creativecommons.org/licenses/by-nc-nd/4.0/)Peer-review under responsibility of the scientific committee of the NAMRI/SME.

Bulk metallic glasses (BMGs) are a new class of amorphous metallic alloys having enhanced mechanical and tribological properties. However, the chip formation behavior of BMGs is not as well established as that of the crystalline materials, which hinders its prospective applications. In this paper, an orthogonal micromachining experiment is conducted, and chip morphology, force signature, hardness, and enthalpy of the machined surface are analyzed. The chips show segmented morphology with distinct fractures. The chip exhibits primary shear zones along with several secondary shear bands emanating within a single segmentation, which evidenced shear localization. Additionally, the machined surface exhibits softening as compared to the undeformed material. The shear localization, responsible for chip segmentation in BMG machining, is assumed to be driven primarily free volume and the shear zone temperature. Hence, a localized chip segmentation model has been formulated incorporating the effects of temperature and free volume generation-induced instabilities. The proposed chip formation model accounts for the contributions of the fracture and the new surface creation energies, in addition to the shear and friction energies used traditionally. The contribution of fracture energy was observed to significant in the chip formation of BMGs. To differentiate between the relative contributions of temperature induced instabilities and free volume generation on shear localization, four distinct regimes were identified based on the critical value of free volume flow coefficient (FVFC) and heat flow coefficients (HFC). The findings demonstrate that if the FVFC is greater than the critical value, significant shear localization takes place. Conversely, the shear localization becomes less pronounced if the FVFC is smaller than the critical values. Thus, it can be deduced that temperature has an insignificant role in shear localization, and free volume acts as the main driver.

Engineered features on pyrolytic carbon (PyC) have been reported to improve the functional performance of the cardiovascular implants. PyC also finds application in thermonuclear components due to its unique directional thermal properties. Note that PyC comprises of stacked layers of brittle graphite-like material and its machining characteristics differ from plastically deformable isotropic materials due to brittle damage and interlaminar decohesion. Consequently, this study is aimed at understanding the mechanics of material removal in the plane of transverse isotropy (horizontally stacked laminae) of PyC via a finite element model. A damaged plasticity material model has been used to capture the effect of material degradation of a brittle material under machining. Uniaxial tension/compression tests have been carried out to calibrate the damaged plasticity model. A surface based cohesive bonding has been used between the layers to simulate the interlaminar decohesion which results in peeling, slipping and delamination during machining. The model predicts the cutting force and thrust forces under different process conditions. The cutting force predictions from the finite element model have been validated against the experimental data for different cutting conditions. In addition, the model also predicts the chip morphology for different machining conditions. The prediction error in the model lies between 2% and 23%. Parametric studies have also been performed to understand the effect of the machining parameters, such as rake angle, uncut chip thickness on the process response. It is found that use of the positive rake angle decreases the cutting forces up to 72%.