Search Results (102)

The article presents a comprehensive review of key issues and challenges related to enhancing the durability of hot forging tools. It discusses modern strategies aimed at increasing tool life, including modifications to tool materials, heat treatment, surface engineering, tool and die design, die geometry, tribological conditions, and lubrication. The review is based on extensive literature data, including recent publications and the authors’ own research, which has been implemented under industrial conditions at the modern forging facility in Forge Plant “Glinik” (Poland). The study introduces original design and technological solutions, such as an innovative concept for manufacturing forging dies from alloy structural steels with welded impressions, replacing traditional hot-work tool steel dies. It also proposes a zonal hardfacing approach, which involves applying welds with different chemical compositions to specific surface zones of the die impressions, selected according to the dominant wear mechanisms in each zone. General guidelines for selecting hardfacing material compositions are also provided. Additionally, the article presents technological processes for die production and regeneration. The importance and application of computer simulations of forging processes are emphasized, particularly in predicting wear mechanisms and intensity, as well as in optimizing tool and forging geometry. Full article

The output energy of Laser Active Optical Systems (LAOSs), in which image brightness is amplified within the laser-active medium, is always higher than the input energy. This contrasts with conventional optical systems (OSs). As a result, a LAOS enables the creation of laser beams with tailored energy distribution across the aperture, making them ideal for material processing applications. This concept was first successfully implemented using metal vapor lasers as the gain medium. In these systems, material processing was achieved by using a laser beam that either carried the required energy profile or the image of the object itself. Later, other laser media were utilized for LAOSs, including barium vapor, strontium vapor, excimer XeCl lasers, and solid-state media. Additionally, during the development of these systems, several modifications were introduced. For example, Space-Time Light Modulators (STLMs) and CCD cameras were incorporated, along with the use of multipass amplifiers, disk-shaped or thin-disk (TD) solid-state laser amplifiers, and other advancements. These techniques have significantly expanded the range of power, energy, pulse durations, and operating wavelengths. Currently, TD laser amplifiers and STLMs based on Digital Light Processor (DLP) technology or Digital Micromirror Devices (DMDs) enhance the potential to develop LAOS devices for Subtractive and Additive Technologies (ST, AT), applicable in both macromachining (cutting, welding, drilling) and micro-nano processing. This review presents comparable characteristics and requirements for these various LAOS applications. Full article

Alloy 625 is a widely utilized nickel-based superalloy known for its excellent mechanical strength and corrosion resistance in aggressive environments. However, its high niobium (Nb) content can lead to the formation of detrimental phases, such as Laves and MC carbides, during welding processes, compromising the mechanical integrity and long-term performance of the weld overlay. This review systematically examines recent research findings on the implications of reducing Nb content in Alloy 625 weld overlays, particularly with respect to microstructure evolution, mechanical behavior, and corrosion performance. Key advancements, including the understanding of segregation behavior, solidification paths, and secondary phase formation, are presented based on recent studies. This paper aims to provide a discussion on the trade-offs and future directions for optimizing Alloy 625 weld overlay claddings through Nb content modification. Full article

High-chromium white iron (HCWI) alloys are often used in industries such as mining which require a high wear resistance. Whilst nitrogen is known as a good austenitic stabiliser, the effects of nitrogen on corrosion properties for welded HCWI have not been studied. Chromium hardfacing alloys were deposited via gas metal arc welding using nitrogen as a shielding gas at flow rates of 5 L/min, 10 L/min, and 15 L/min. The corrosion behaviour of these modified alloys was studied using electrochemical techniques such as potentiodynamic measurements and electrochemical impedance spectroscopy. Higher gas flow rates were found to increase the volume fraction of the eutectic austenite while reducing the amounts of eutectic carbides. Nitrogen did not transform the M₇C₃ (M = Cr, Fe) carbides into any other form of carbides. The sample without nitrogen as a shielding gas was found to display the worst corrosion resistance after electrochemical testing, such as corrosion resistance parameters in EIS tests. Higher nitrogen shielding gas flow rates were found to produce higher levels of corrosion resistance; this was especially true for the 15 L/min sample with a corrosion resistance parameter to EIS that was more than double that of the sample without nitrogen shielding gas (e.g., 4700 vs. 2325 Ω·cm² respectively). Full article

In this study, based on previous fundamental research on weldability, we ultimately aim to propose a filler metal that enables hot crack-free repair welding of 247LC superalloy while minimizing compositional modification. First, we investigated the liquation cracking susceptibility of two candidate filler metals, namely Hf-free and B-free 247LC superalloy welds, by individually removing Hf and B and performing a spot-Varestraint test. As a result, the liquation cracking temperature range (LCTR) of B-free 247LC was 370 K and 230 K for Hf-free 247LC. The results indicated a significant reduction in the liquation cracking temperature range (LCTR) to 230 K for the Hf-free alloy, from 620 K for the Hf-containing standard 247LC alloy. Direct microstructural analysis of the liquation cracking surfaces revealed a higher liquation initiation temperature at the γ/MC interface in the Hf-free alloy, ranging from 1460 to 1600 K, compared to that of the original 247LC alloy composition, which contributed to the reduced LCTR. These findings indicate that Hf-free 247LC superalloys offer enhanced weldability—particularly for manufacturing and repairing critical components of tools with high-temperature applications, such as gas-turbine blades. Finally, assuming the Hf-free 247LC alloy as a filler metal and the original 247LC alloy composition as a base metal, double square groove welding was performed. This clearly confirmed the possibility of hot crack-free welding with Hf-free 247LC filler metal, effectively suppressing both liquation and solidification cracking simultaneously. Full article

The conventional near-infrared laser transmission welding (LTW) process for joining dissimilar transparent polymers is limited by the need to incorporate optical absorbents, which compromises joint performance and raises biocompatibility concerns. To address these issues, this study proposed a surface modification technique using femtosecond laser ablation prior to the welding process. Experiments involved 520 nm femtosecond laser ablation of transparent polymers, followed by LTW of dissimilar transparent polymers using an 808 nm laser, with subsequent characterization and mechanical property evaluations. A maximum joint strength of 13.65 MPa was achieved. A comprehensive investigation was conducted into the physical and chemical mechanisms through which laser ablation improved the welding performance of dissimilar transparent polymers. The results demonstrated that laser ablation generated microstructures that serve as substitutes for optical absorbents while also facilitating the formation of numerous oxygen-containing functional groups. These enhancements improve miscibility and bonding performance between dissimilar polymers, enabling absorbent-free welding between ablated polycarbonate (PC) and polystyrene (PS). This work confirms both the feasibility and potential application of this process for direct LTW of dissimilar transparent polymers. Full article

Fusion-welded austenitic stainless steel (ASS) was predominantly employed to manufacture dry storage canisters (DSCs) for the storage applications of spent nuclear fuel (SNF). However, the ASS weld joints are prone to chloride-induced stress corrosion cracking (CISCC), a critical safety issue in the nuclear industry. DSCs were exposed to a chloride-rich environment during storage, creating CISCC precursors. The CISCC failure leads to nuclear radiation leakage. Therefore, there is a critical need to enhance the CISCC resistance of DSC weld joints using promising repair techniques. This review article encapsulates the current state-of-the-art of peening techniques for mitigating the CISCC in DSCs. More specifically, conventional shot peening (CSP), ultrasonic impact peening (UIP), and laser shock peening (LSP) were elucidated with a focus on CISCC mitigation. The underlying mechanism of CISCC mitigation in each process was summarized. Finally, this review provides recent advances in surface modification techniques, repair techniques, and developments in welding techniques for CISCC mitigation in DSCs. Full article

Laser welding (sealing) is a promising technology for joining metal to glass, but it shows poor joint strength in existing studies. This study conducted the laser sealing of a 304 stainless steel alloy to high-alumina glass using pre-oxidation and laser surface melting as an interlayer. The present investigation aimed to determine the influence of this surface modification strategy on the mechanical behavior of glass-to-metal sealing joints made via laser welding. An experimental campaign was conducted on 304 stainless steel and high-alumina glass. Pre-oxidation and laser surface melting treatment were performed on the 304 steel alloy surface before joining to improve the mechanical interlock and chemical bonding between the substrates. The microstructures of the 304 steel alloy/glass interface were investigated by using scanning electron microscopy (SEM) and an energy-dispersive spectrometer (EDS), and the interface evolution mechanism and the correlation between the steel/glass joining strength and the interface morphology were discussed. Finite element analysis software simulated the temperature field and stress field in the welding process, and the reasons for the differences in the welding strengths of different surface treatment samples were analyzed in depth. The results showed that the laser surface melting strategy used significantly influenced the mechanical behavior of the joints and the failure mode. Adopting a higher number of scans improved the mechanical interlock and, consequently, the mechanical behavior of the joints. Full article

The rise of Industry 4.0 has introduced challenges and new production models like additive manufacturing (AM), enabling the creation of complex objects previously unattainable. However, many polymers remain underutilized due to the need for improved mechanical properties and reduced process-induced anisotropy. ME-based part construction involves successive filament deposition, akin to welding. Upon exiting the nozzle, the polymer solidifies within seconds, limiting the time and temperature available for diffusion and efficient bonding with the adjacent filament. Therefore, optimizing this welding process is essential. The primary objective of this review was to report on the equipment utilized to enhance the bonding between filaments deposited during manufacturing. While higher temperatures improve welding, most equipment cannot endure prolonged high-heat operations, limiting the use of engineering-grade polymers. Modifying polymer matrices by incorporating low-molar-mass molecules can boost welding and mechanical strength. Significant gains in mechanical properties have come from matrix modifications and new in situ welding devices. Reported devices use light (laser, UV IR), electric current, radio frequency and heat collection from the nozzle. The simplest device is a heat collector, while a double laser beam system has achieved the highest mechanical properties without matrix modification. There was an improvement in properties ranging from 20% to 200%. Full article

In this study, we report, for the first time, to the best of our knowledge, on in-volume glass modifications produced by GHz bursts of femtosecond pulses. We compare three distinct methods of energy deposition in glass, i.e., the single-pulse, MHz burst, and GHz burst regimes, and evaluate the resulting modifications. Specifically, we investigate in-volume modifications produced by each regime under varying parameters such as the pulse/burst energy, the scanning velocity, and the number of pulses in the burst, with the aim of establishing welding process windows for both sodalime and fused silica. Full article

This study investigates the residual stresses arising from welding and machining processes, recognizing their adverse implications in manufacturing. Employing experimental analysis and simulation techniques, the research scrutinizes residual stress alterations resulting from sequential butt welding and subsequent machining. Utilizing MSC Marc Mentat software(version 2016), three-dimensional models are developed to simulate these processes. The finite element model from welding simulation seamlessly integrates into cutting simulations via the pre-state option. The experimental procedures involve 100 × 100 × 10 mm AISI 304 steel plates subjected to sequential welding and machining, with residual stresses measured at each stage. A comparative analysis between experimental and simulation results elucidates variations in residual stresses induced by sequential processes. The study focuses on examining the initial stress state post-welding and numerically assessing stress modifications due to milling. The results suggest minimal material removal insignificantly affects stress distribution and magnitude at the weld centerline. However, increased material removal leads to noticeable changes in through-thickness transverse stress within the weld zone, contrasting with marginal alterations in through-thickness longitudinal stress. Regions distanced from the weld seam show substantial increases in through-thickness longitudinal stress compared to marginal changes in through-thickness transverse stress. Full article

The main directions and fields of the application of metal nanopowders in joining technologies are considered. Based on this analysis, the purpose of this research was to determine the effect of tungsten nanopowder on the structure and properties of the deposited metal. In order to increase the efficiency of using tungsten nanopowder for modification, it is necessary to ensure the introduction of nanopowder into the low-temperature zone of the molten metal during surfacing. To study the metal, microstructural analysis was performed, and the microhardness of the deposited joint was determined. On the basis of the conducted studies, a change in the structure of the deposited metal and an increase in mechanical properties were revealed. A conclusion is made about the effect of tungsten nanopowder on the metal modification process during manual metal arc, metal inert gas, and flux-cored arc welding. Based on the conducted studies, it was found that the introduction of tungsten nanopowder into the low-temperature zone of the molten metal ensures the modification of the surfacing and induces an increase in the microhardness of the deposited metal. At the same time, grains of polyhedral morphology are formed at the surface, and the structure of oriented dendrites at the boundary of fusion with the base metal is also revealed, showing the peculiarities of the distribution of microhardness in various surfacing methods. The minimum and maximum values of microhardness depend not only on the nanopowder but also on the method of its introduction into the molten metal. Full article

Dissimilar welding between aluminum and copper poses significant challenges, primarily due to differences in their thermal and mechanical properties, resulting in brittle intermetallic compounds, limited joint strength, and high electrical resistivity. This study aims to overcome these issues by employing Ag-18Cu-10Zn filler material and optimizing laser power with a focus on improving joint strength and electrical conductivity. The results indicate that the incorporation of silver and zinc enhances the phase composition and microstructure of the weld. By forming solid solution phases such as Ag₂Al and Cu₅Zn₈, the brittle Al₂Cu phase commonly found in traditional Al/Cu welding is replaced. This not only promotes the heterogeneous nucleation of fine silver-rich grains but also restricts the excessive growth of silver-poor grains, resulting in a uniform distribution of fine grains throughout the weld. These modifications contribute to both fine-grain strengthening and dispersion strengthening. At an optimal laser power of 750 W, joint strength reaches 109 MPa, while joint resistivity decreases to 3.19 μΩ·cm, 12.6% lower than that of the aluminum alloy base material. This study proposes a process for achieving highly conductive, reliable Al/Cu dissimilar metal joints, potentially impacting the aluminum–copper connections in battery modules for new energy vehicles. Full article

Among the many methods of joining different materials, gluing is characterized by its most specific nature. In comparison with, for example, welded, screwed, or overlapped connections, a glued connection depends on the largest number of factors. Many of them are related to the phenomenon of adhesion, which is complicated by definition. It has many shapes and forms, and its existence determines not only the durability of such a joint but also the possibility of its execution. Epoxy polymers are among the most commonly used adhesives. Their extremely good parameters can be easily modified by additives in the form of fillers. Compatibility between the filler and the adhesive allows for further improving the adhesive parameters in the glued joint. However, in order to effectively combine the adhesive and the filler, different, often specific mixing methods must be used. The following study presents the results obtained in an experimental research program, the aim of which was to increase the adhesion of epoxy resin to a properly prepared concrete substrate. As a method to increase the final adhesion, the addition of microsilica and carbon nanotubes in an experimentally determined amount was selected. The use of sonication as a mixing method together with cavitation allowed for improving the parameters which determine the final adhesion of the adhesive to concrete. The parameters which were selected to describe the course of changes in the adhesion of the adhesive to the concrete substrate were the viscosity, free surface energy, surface parameters, adhesion, and SEM images of the tested resin in various modification configurations. The obtained results make it possible to form stronger and more durable adhesive joints during the reinforcement of concrete structural elements using fiber-reinforced polymer (FRP) composites. Full article

Hermetic glass-to-metal sealing (GMTS) technology combines metal and glass and can be used to construct vacuum tubes; electric discharge tubes; semiconductor diodes; reed switches; and pressure-tight glass-to-metal windows, optical windows, and lenses in electronics or electronic systems. The hermetic and mechanically strong seals engineered using GTMS are highly reliable, making them suitable for deployment in harsh environments and for applications requiring high performance. However, it has always been challenging to precisely and robustly join glass and metal due to the significant disparities in their properties. In this study, the laser transmission welding of borosilicate glass and aluminum alloy using a pulsed Nd:YAG laser to achieve hermetic glass–metal seals was experimentally investigated. This research focused on various processing parameters and the influence of surface conditions on bonding quality. Three different types of surfaces—a polished surface, a surface subjected to preoxidation, and a laser-modified surface—were compared. To evaluate the weld strength, shear-tensile separation forces were measured. The analysis of fracture and separation encompassed detailed examinations of the weld morphology, microstructure, and elemental composition. The results revealed that increasing the laser welding energy initially enhanced the weld strength until a saturation point was reached. Among the three different surface treatments tested, the laser surface modification of aluminum alloy yielded the highest weld strength. The maximum achieved bond force exceeded 35.38 N, demonstrating the feasibility of using cost-effective pulsed laser welding for glass-to-metal sealing. The results were significantly better than those from previous research in which aluminum alloy surfaces were pretreated using microarc oxidation. Full article