Search Results (23)

The Charpy impact resistance of monolithic high-strength and dissimilar structured steel was studied. A gas metal arc welding process was used to fabricate the structured steel by depositing a layer of austenitic stainless steel, followed by a layer of hardfacing material over the high-strength steel plate. ANSYS LS-DYNA^TM was used to simulate pendulum–striker impacts on steel Charpy samples. A Cowper–Symonds constitutive model was employed to capture the strain rate behavior. The corresponding material constitutive model parameters were obtained from the literature for the monolithic materials; an iterative numerical optimization method was used to couple the parameters of the structured steel simulation and experimental results. Numerical simulation results showed close agreement with experimental ones. Simulation is a valuable tool for explaining the fracture mechanism in the Charpy impact test and can be used to efficiently design parts made of structured steel that will be subjected to impacts or high-speed deformations. Full article

Direct fusion welding of aluminum (Al) to magnesium (Mg) results in the formation of brittle intermetallic compounds (IMCs) that significantly restrict the application of these joints in structural applications. In this study, cold spray, a promising solid-state coating deposition technology, was employed to introduce a nickel (Ni) interlayer to facilitate joining of Al to Mg sheets by means of resistance spot welding (RSW). The ability of cold spraying to deposit metallic powder on the substrate without melting proves beneficial in mitigating the formation of the Al-Mg IMCs. The Ni-coated coupons were subsequently welded via resistance spot welding at optimized parameters: 27 kA for 15 cycles in two pulses with a 5-cycle inter-pulse delay. Scanning electron microscopy confirmed metallurgical bonding between the Al, Mg, and Ni coatings in the fusion zone. It is shown that the bonding between the three elements inhibits the formation of deleterious IMCs. Tensile shear testing showed joint strength exceeding 4.2 kN, highlighting the potential of the proposed cold spray RSW approach for dissimilar joining in structural applications. Full article

The friction surfacing (FS) process has emerged over the past few years as a method for joining both similar and dissimilar materials, for volume damage repair of defective components, and for corrosion protection. The possibility to produce a metallic coating by FS, without melting the material, classifies this technique as distinct from other standard methods. This unconventional deposition method is based on the severe plastic deformation that appears on a rotating metallic rod (consumable material) pressed against the substrate under an axial load. The present study aims to investigate the tribological properties and corrosion resistance provided by the aluminum-based FS coatings deposited onto a structural S235 steel substrate and further modified by plasma electrolytic oxidation (PEO). During the PEO treatment, the formation of a ceramic film is enabled, while the hardness, chemical stability, corrosion, and wear resistance of the modified surfaces are considerably increased. The morpho-structural characteristics and chemical composition of the PEO-modified FS coatings are further investigated using scanning electron microscopy combined with energy dispersive spectroscopy analysis and X-ray diffraction. Dry sliding wear testing of the PEO-modified aluminum-based coatings was carried out using a ball-on-disc configuration, while the corrosion resistance was electrochemically evaluated in a 3.5 wt.% NaCl solution. The corrosion rates of the aluminum-based coatings decreased significantly when the PEO treatment was applied, while the wear rate was substantially reduced compared to the untreated aluminum-based coating and steel substrate, respectively. Full article

CuCrZr/GH4169 multi-material structures combine the high thermal conductivity of copper alloys with the high strength of nickel-based superalloys, making them suitable for aerospace components that require efficient heat dissipation and high strength. However, additive manufacturing of such dissimilar metals faces challenges, with each laser powder bed fusion (LPBF) and laser directed energy deposition (LDED) process having its limitations. This study employed an LPBF-LDED integrated additive manufacturing (LLIAM) approach to fabricate CuCrZr/GH4169 components. CuCrZr segments were first produced by LPBF, followed by LDED deposition of GH4169 layers using optimized laser parameters. The microstructure, composition, and mechanical properties of the fabricated components were analyzed. Results show a sound metallurgical bond at the CuCrZr/GH4169 interface with minimal porosity and cracks (typical defects at the interface), achieved by exceeding a threshold laser energy density. Elemental interdiffusion forms a 100–200 μm transition zone, with a smooth hardness gradient (97 HV0.2 to 240 HV0.2). Optimized specimens exhibit tensile failure in the CuCrZr region (234 MPa), confirming robust interfacial bonding. These findings demonstrate LLIAM’s feasibility for CuCrZr/GH4169 and underscore the importance of balancing thermal conductivity and mechanical strength in multi-material components. These findings provide guidance for manufacturing aerospace components with both high thermal conductivity and high strength. Full article

The automotive and aerospace industries increasingly rely on lightweight, high-strength materials to improve fuel efficiency, making the joining of dissimilar metals such as aluminum and steel both beneficial and essential. However, a major challenge in these joints is the formation of brittle intermetallic compounds (IMCs) at the interface, even when using low heat-input solid-state welding methods like friction stir welding (FSW). Furthermore, IMC growth at elevated temperatures significantly limits the service life of these joints. In this study, an intermediate layer of stainless steel was deposited on the steel surface prior to FSW with aluminum. The resulting Al–Steel joints were subjected to heat treatment at 400 °C and 550 °C to investigate IMC growth and its impact on mechanical strength, with results compared to conventional joints without the intermediate layer. The intermediate layer significantly suppressed IMC formation, leading to a smaller reduction in mechanical strength after heat treatment. Joints with the intermediate layer achieved their highest strength (350 MPa) after heat treatment at 400 °C, while conventional joints exhibited their highest strength (225 MPa) in the as-welded condition. At 550 °C, both joint types experienced a decline in strength; however, the joint with the intermediate layer retained a strength of 100 MPa, whereas the conventional joint lost its strength entirely. This study provides an in-depth analysis of the role of IMC growth in joint strength and demonstrates how the intermediate layer enhances the thermal durability and mechanical performance of Al–Steel joints, offering valuable insights for their application in high-temperature environments. Full article

In order to solve the problem of a thin deposition layer on the titanium alloy in the traditional friction surfacing process of dissimilar Ti/Al metals, new shoulder-restricted friction deposition (SRFD) equipment was successfully developed by introducing a restricted shoulder. Using a laser to roughen the titanium substrate, the process verification of Al deposition onto TC4 was realized. The material utilization was close to 100%, and a deposition layer with a thickness of 0.8 mm and a strong bonded interface was obtained. The peel strength of the triple-layer deposited joints was 121 MPa. Full article

A few components used in the aerospace and petrochemical industries serve in corrosive environments at high temperatures. Corrosion-resistant metals or unique processes, such as coating and fusion welding, are required to improve the performance of the parts. We have used laser powder bed fusion (LPBF) technology to deposit a 5 mm thick corrosion-resistant CoCrMo layer on a high-strength IN625 substrate to improve the corrosion resistance of the core parts of a valve. This study found that when the laser volumetric energy density (E_V) ≤ 20, the tensile strength increases linearly with the increase in E_V, and the slope of the curve is approximately 85°. The larger the slope, the greater the impact of E_V on the intensity. When E_V > 20, the sample strength reaches the maximum tensile strength. When the E_V increases from 0 to 20, the fracture position of the sample shifts from CoCrMo to IN625. When E_V ≤ 38, the strain increases linearly with the increase in E_V, and the slope of the curve is approximately 67.5°. The sample strain rate reaches the maximum when E_V > 38. Therefore, for an optimal sample strength and strain, E_V should be greater than 38. This study provides theoretical and technical support for the manufacturing of corrosion-resistant dissimilar metal parts using LPBF technology. Full article

Dissimilar metal samples of TC4/TiAl were successfully prepared by laser additive manufacturing (LAM) technology, with pure vanadium as the interlayer. The microstructure, phase composition, element distribution and mechanical properties at the interface of TC4/V and TiAl/V were analyzed by optical microscope (OM), scanning electron microscope (SEM) and backscattering diffraction (EBSD). The experimental results showed that the interface microstructure of TiAl/V is mainly composed of γ, α₂ phase and V solid solution. The microstructure of the TC4/V interface is mainly composed of β-Ti and V solid solution. There are no holes, metallurgical defects or microcracks at the above two interfaces, and the interface is bonded well. With the increase in the number of deposition layers, the interface bonding depth increases, and its thickness increases from 30 μm to 80 μm. The mechanical properties tests showed that the tensile strength and elongation of dissimilar metals with two layers of V interlayer TC4/TiAl are the highest, and their values are 483 MPa and 0.35%, respectively. Compared with the one-layer V intermediate layer sample (tensile strength 405 MPa, elongation 0.24%), the tensile strength and elongation are increased by 19.2% and 45%, respectively. The tensile strength and elongation of dissimilar metals in three-layer V interlayer TC4/TiAl are the lowest, and their values are 350 MPa and 0.16%. Full article

The suitability of the direct energy deposition process of exothermic powders Fe-Ti in joining dissimilar metals to produce small parts of a complete shape for various applications is considered. The procedure of the direct energy deposition of commercial pure iron and titanium in various proportions and the modes of the process are described. Optical microscopy and SEM with EDX analysis, X-ray analysis, and microhardness measurements of laser-fabricated intermetallics are applied. Intermetallic compounds of FeTi, Fe₂Ti, eutectoids, complex titanium oxides and nitrides, and iron carbides are found. Interlayer and trans-layer cracks and pores are observed. A microhardness growth from 150 HV to 900 HV was obtained for all samples due to the precipitation of brittle intermetallic phases in the gradient Fe-Ti system during the DED. The dispersion of microhardness values becomes significant in Ti-rich areas; there, pores and cracks are found. The revealed structure features are considered in relation to published results and explained. Increased concentrations of Ti to Ti + Fe = 3:1 on the Fe- and Fe + Ti -substrate with concentrations of Ti + Fe = 1:1 and Ti + Fe = 1:3 lead to increasing hardness and its distribution, but also increases in residual microstress. Recommendations are given to reduce the power during the direct energy deposition of titanium layers and to apply Fe-substrate, which can reduce residual stress, pores, and cracks. Full article

Bimetallic structures manufactured by direct deposition have a defect due to the sudden change in the microstructure and properties of dissimilar metals. The laser metal deposition (LMD)-wire arc additive manufacturing (WAAM) process can alleviate the defect between two different materials by depositing the functionally graded material (FGM) layer, such as a thin intermediate layer using LMD and can be used to fabricate bimetallic structures at high deposition rates with relatively low costs using WAAM. In this study, the LMD-WAAM process was performed, and the microstructure of the fabricated bimetallic structure of IN625-SUS304L was investigated. The microstructure of the FGM zone of the LMD-WAAM sample was mainly fine equiaxed dendrite morphologies. In contrast, coarse columnar dendrite morphologies constituted the WAAM zone. The composition of the major alloying elements of the LMD-WAAM sample gradually changed with the height of the deposited layer. The microhardness of the LMD-WAAM sample tended to increase with an increasing Inconel content. In the case of the LMD-WAAM sample, the fracture occurred near the interface between 25% IN625 and 0% IN625; in the WAAM sample, the final fracture occurred in SUS304L near the interface. The tensile strength of the LMD-WAAM samples was inversely proportional to the laser power. The results showed that the LMD-WAAM samples had 8% higher tensile strength than the samples fabricated using only WAAM. Full article

Pure titanium (Ti) ERTi-2 was accumulated on an aluminum (Al) alloy ER5356 component via wire and arc additive manufacturing. The effect of processing parameters, mainly the input heat per unit length, on Ti/Al components was investigated. The microstructure of the Ti deposited layer and the Ti/Al reaction layer was analyzed using optical microscopy, scanning electron microscope, energy-dispersive spectroscopy, and an X-ray diffractometer. The fabrication of the surface layer equivalent to pure Ti as the used wire or Ti-Al alloy on the Al alloy components was achieved under low and high input heat conditions, respectively, although the Ti/Al components had low joinability and cracks at the reaction layer. Finally, the potential of additive-manufactured Ti/Al components with reference to our results and previous reports was discussed. Full article

Additive Friction Stir Deposition (AFSD) is a recent innovation in non-beam-based metal additive manufacturing that achieves layer-by-layer deposition while avoiding the solid-to-liquid phase transformation. AFSD presents numerous benefits over other forms of fusion-based additive manufacturing, such as high-strength mechanical bonding, joining of dissimilar alloys, and high deposition rates. To improve, automate, and ensure the quality, uniformity, and consistency of the AFSD process, it is necessary to control the temperature at the interaction zone and the force applied to the consumable feedstock during deposition. In this paper, real-time temperature and force feedback are achieved by embedding thermocouples into the nonconsumable machine tool-shoulder and estimating the applied force from the motor current of the linear actuator driving the feedstock. Subsequently, temperature and force controllers are developed for the AFSD process, ensuring that the temperature at the interaction zone and the force applied to the feedstock track desired command values. The temperature and force controllers were evaluated separately and together on setpoints and time-varying trajectories. For combined temperature and force control with setpoints selected at a temperature of 420 °C and a force of 2669 N, the average temperature and force tracking errors are 5.4 ± 6.5 °C (1.4 ± 1.6%) and 140.1 ± 213.5 N (5.2 ± 8.0%), respectively. Full article

The development of a laser cladding repair strategy is critical for the continued growth of heavy-haul railway networks. Premium hypereutectoid rails have undergone laser cladding using a new martensitic stainless-steel alloy, 415SS, developed for high carbon rails after standard cladding metals were found to be incompatible. Non-destructive neutron diffraction techniques were used to measure the residual stress in different layers generated across a dissimilar metal joint during laser cladding. The internal stress distribution across the cladding, heat-affected zone (HAZ), and substrate was measured in the untempered rail, after 350 °C and 540 °C heat treatment procedures and two surface grinding operations. The martensitic 415SS depositions produce compressive stress in the cladding, regardless of tempering procedures, which may inhibit fatigue crack propagation whilst grinding operations locally relive surface stress. Balancing tensile stresses were recorded below the fusion boundary in the HAZ due to thermal gradients altering the microstructure. The combination of 540 °C tempering and 0.5 mm surface layer removal produced a desirable combination of compression in the cladding deposition with significantly reduced tensile stresses in the HAZ. A comparison with the current literature shows that this alloy achieves a unique combination of desirable hardness, low tensile stress, and compression in the cladding layer. Data obtained during strain scanning has been used to determine the location of microstructural changes at the fusion boundary and HAZ through correlation of the stress, strain, full width at half maximum (FWHM), and intensity profiles. Therefore, neutron diffraction can be used for both the accurate measurement of internal residual stress and to obtain microstructural information of a metallurgical join non-destructively. Full article

Friction welding (FRW) is a promising method for joining cylindrical components of dissimilar and similar polymers or metals. In particular, FRW is capable of generating defect-free welds. Fused deposition modeling (FDM) has been widely employed in the automotive industry, ranging from lightweight tools, testing models, and functional parts. Conventionally, dissimilar parts fabricated by FDM are joined by glue. However, distinct disadvantages of this approach include both low joining strength and low joining efficiency. Hitherto, little has been reported on the characterizations of weld strength of FRW of dissimilar parts fabricated by FDM. In addition, FRW of dissimilar polymeric materials is a difficult task because different polymers have different physical, rheological, and mechanical properties. In this study, the effects of welding revolution on the weld strength of friction welding dissimilar parts fabricated by FDM are investigated experimentally. It was found that the average flexural strength of dissimilar polymer rods fabricated by FRW is about 1.52 times that of dissimilar polymer rods fabricated by gluing. The highest flexure strength can be obtained by FRW using polylactic acid (PLA) and PC (polycarbonate) rods. The average impact strength of dissimilar polymer rods fabricated by FRW is about 1.04 times that of dissimilar polymer rods joined by gluing. The highest impact strength can be obtained by FRW using PLA to PLA rods. Full article

Recent advances in laser technologies offer significant flexibility in the additive manufacturing domain. Extensive work was focused on material processing using laser-directed energy deposition for repairing parts. This pilot study investigated the use of selective laser melting (SLM) for depositing a superior material such as CoCr on an existing stainless steel base. The interface between these dissimilar materials was analyzed. During fabrication, both metals were gradually mixed in the liquid state as the first CoCr powder layer was melded on the steel base without obvious defects. According to SEM and EDAX, the heat-affected zone has a limited depth (<20 µm). XRD patterns recorded across the CoCr–304 interface show a homogenous mixture of γ(Fe) and α(Co) solid solutions. The microporosity calculated by CT was under 0.5%. Microhardness was measured at and near the interface region, showing that the intermixing zone has high hardness (470–480 HV1), which may be related to the fine-grained microstructure. Mechanical testing reveals that the adhesion strength at rupture is 35% higher compared with the ultimate tensile strength of 304 steel. This adhesion strength can be attributed to the complete melting of CoCr particles after laser irradiation and to the reduced thickness of the HAZ and the IZ. Full article