Search Results (40)

In this study, a brazed diamond micro-powder grinding wheel with Ni-based filler metal was fabricated, which achieved one-step grinding forming of YG-6 cemented carbide rods. The interfacial microstructure, elemental diffusion behavior, and interfacial phases of the brazed diamond micro-powder joint were systematically characterized. Furthermore, the machining performance of the brazed diamond micro-powder grinding wheel was comprehensively evaluated in combination with its service life and the surface roughness of the machined YG-6 cemented carbide rods. The results show that the Ni-based filler exhibits good wettability to diamond micro-powder particles, and the diamonds have a reasonable protrusion height in the filler layer, with no graphitization observed on the surface of the brazed diamonds. During the brazing process, the active element Cr continuously segregates toward the diamond surfaces and reacts progressively with dissolved C atoms on the diamond surfaces, eventually forming a lath-shaped Cr–C compound layer on the diamond surfaces. XRD results identify this compound as Cr₃C₂. Elemental diffusion occurs between the filler layer and the steel substrate, forming a Fe–Ni solid solution diffusion zone. Consequently, the Ni-based filler forms a reliable chemical metallurgical bond with both the diamond micro-powder particles and the steel substrate. The as-prepared brazed diamond micro-powder grinding wheel exhibits excellent service life: a single wheel can grind more than 1300 YG-6 cemented carbide rods on average before failure. The surface roughness (Ra) of the machined YG-6 cemented carbide workpieces remains below 1.6 μm throughout all processing stages, which satisfies the requirements for one-step precision grinding. Full article

Four compositions of rapidly quenched ribbon brazing alloys based on Ag–Cu–Ti (Ag–26.5Cu–1.5Ti, Ag–25Cu–5Ti) and Ag–Cu–Zr (Ag–26.5Cu–1.5Zr, Ag–25Cu–5Zr) systems were produced. Initial ingots were synthesized by arc melting. Rapidly solidified ribbons, 50–100 μm thick, were then fabricated from homogenized ingots using a “Crystall-702” facility. A comparative analysis of the microstructure and phase composition of both the ingots and ribbons was conducted using scanning electron microscopy and X-ray diffraction. The analysis revealed the presence of Cu₄Ti and CuTi intermetallic compounds in the Ag–Cu–Ti alloys, and AgCu₄Zr and Zr₂Cu in the Ag–Cu–Zr alloys. Rapid quenching was found to produce metastable structures and significantly refine the intermetallic phases. Microhardness measurements of the ingot and ribbon states demonstrated a substantial influence of the processing route on the mechanical properties. The tensile strength of the ingots was also evaluated. The wetting angles of the rapidly quenched alloy melts on 99% Al₂O₃ (alumina) ceramic substrates under vacuum were determined. All produced ribbons, except for the Ag–26.5Cu–1.5Zr composition, demonstrated adequate wettability. Thus, these materials are considered promising for further research into heat-resistant metal–ceramic joints. Full article

The bonding behavior of the Ni-based superalloy CM247LC during transient liquid phase (TLP) bonding is strongly governed by filler metal chemistry, particularly boron activity. In this study, the time-dependent bonding mechanisms of CM247LC joints fabricated using a high-boron MBF-80 filler and a low-boron MBF-20 filler are systematically compared to clarifying the transition between reaction-dominated brazing and diffusion-assisted TLP bonding. Microstructural analyses reveal that MBF-80 promotes the formation of a persistent, reaction-stabilized interlayer characterized by strong boron localization and the development of boron-rich intermetallic reaction products. These features kinetically suppress diffusion-assisted homogenization and prevent isothermal solidification, resulting in pronounced chemical and mechanical discontinuities across the joint. In contrast, MBF-20 enables progressive boron depletion, suppression of stable intermetallic accumulation, and interfacial smoothing, leading to diffusion-assisted chemical redistribution and partial isothermal solidification. This evolution is accompanied by gradual convergence of hardness profiles toward that of the CM247LC base metal, indicating improved mechanical continuity. These results demonstrate that joint hardness alone is insufficient for evaluating bonding quality in CM247LC. Instead, controlled microstructural evolution governed by low-boron filler chemistry is essential for achieving chemically and mechanically compatible joints. The present work establishes a clear mechanistic link between filler metal composition and bonding behavior, providing guidance for the design of reliable TLP bonding strategies in Ni-based superalloys. Full article

During active brazing of alumina ceramics, active elements react with the ceramic to form a reaction layer, which has significant influence on the mechanical property of the brazed joint. However, the composition and formation mechanism of this layer remain unclear among researchers. To fill this gap, different brazing temperatures (900–1100 °C) and heating rates (2.5 °C/min and 10 °C/min) were used to braze 95% Al₂O₃ ceramics and a Kovar 4J34 alloy using a Ag-Cu-2Ti active brazing filler, and the microstructure and mechanical properties of the joints were investigated. The results show that the joint could be divided into five layers: Al₂O₃, ceramic-side reaction layer, filler layer, Kovar-side reaction layer, and Kovar. The ceramic-side reaction layer could be further divided into a Ti-O-rich layer and an intermetallics (IMC)-rich layer, and the Kovar-side reaction layer consists of TiFe₂ particles, Ag-Cu eutectic, and the remaining Kovar. A belt-like TiFe₂+TiNi₃ IMC could be found in the filler layer. Increasing the brazing temperature enlarged the belt-like TiFe₂+TiNi₃ IMC in the filler layer and increased the thickness of the IMC-rich layer in the ceramic-side reaction layer, but had no significant effect on the thickness of the Ti-O-rich layer in the ceramic-side reaction layer. A lower heating rate (2.5 °C/min) was found to suppress the formation of the IMC-rich layer and shift the fracture location in shear tests from the ceramic-side reaction layer to the filler layer, indicating that the strength of the ceramic-side reaction layer was enhanced by controlling the formation of the IMC-rich layer. A maximum shear strength of 170 ± 61 MPa was obtained at a heating rate of 2.5 °C/min and a brazing temperature of 940 °C. Full article

In order to enhance the heat dissipation of a chip, this work investigates the enhancement of the thermal homogenization effect of a ceramic substrate with a high-thermal-conductivity graphene material to improve the interfacial heat transfer performance. AgCuTi-activated brazing material is used to connect the graphene film/AlN. The mechanism of the influence of brazing temperatures on the microstructure and thermal conductivity of joints is discussed. The thermal conductivity of the graphene/AlN double layer composite brazed at 890 °C for 10 min holding time was the highest at 482.3 W m⁻¹ K⁻¹. This study provides a new solution for the application of AlN ceramics in high-heat-flow scenarios. Full article

A novel AgCuTi brazing foil with a unique microstructure was developed, which could achieve strong vacuum brazing of Ti6Al4V (TC4) and sapphire. The brazing foil was composed of Ag solid solution (Ag(s,s)), Cu solid solution (Cu(s,s)), and layered Ti-rich phases, and had a low liquidus temperature of 790 °C and a narrow melting range of 16 °C, facilitating the defect-free joining of TC4 and sapphire. The sapphire/TC4 joint fabricated by using this novel AgCuTi brazing foil exhibited an outstanding average shear strength of up to 132.2 MPa, which was the highest value ever reported. The sapphire/TC4 joint had a characteristic structure, featuring a brazing seam reinforced by TiCu particles and a thin Ti₃(Cu,Al)₃O reaction layer of about 1.3 μm. The fracture mechanism of the sapphire/TC4 joint was revealed. The crack originated at the brazing seam with TiCu particles, then propagated through the Ti₃(Cu,Al)₃O reaction layer, detached the reaction layer from the sapphire, and finally penetrated into the sapphire. This study offers valuable insights into the design of active brazing alloys and reliable metal–ceramic bonding. Full article

Brazing a SiO_2f/SiO₂ composite with metals is often faced with two problems: poor wettability with the brazing alloy and high residual stress in the joint. To overcome these problems, we report a combined method of selective etching and depositing reduced graphene oxide (rGO) on the surface of a SiO_2f/SiO₂ composite (3D-rGO-SiO_2f/SiO₂) to assist brazing with TC4. After the combined treatment, a “3D-rGO” buffer layer formed on the surface layer of the SiO_2f/SiO₂, and the contact angle was reduced from 130° to 38°, which meant the wettability of active brazing alloy on the surface of SiO_2f/SiO₂ was obviously improved. In addition, the “3D-rGO” buffer layer contributed to fully integrating the brazing alloy and SiO_2f/SiO₂; then, the infiltration of the brazing alloy into the surface layer of the SiO_2f/SiO₂ was enhanced and formed the reduced graphene oxide with a pinning structure in the three dimensional (“3D-pinning-rGO”) structure. Moreover, the joining area of the brazing alloy and SiO_2f/SiO₂ was expanded and the mismatch degree between the SiO_2f/SiO₂ and TC4 was reduced, which was achieved by the “3D-pinning-rGO” structure. Furthermore, the concentration of the residual stress in the SiO_2f/SiO₂-TC4 joints transferred from the SiO_2f/SiO₂ to the braided quartz fibers, and the residual stress reduced from 142 MPa to 85 MPa. Furthermore, the 3D-pinning-rGO layer facilitated the transfer of heat between the substrates during the brazing process. Finally, the shear strength of the SiO_2f/SiO₂-TC4 joints increased from 12.5 MPa to 43.7 MPa by the selective etching and depositing rGO method. Full article

The manufacturing of active RF devices like klystrons is dominated by expensive and time-consuming cycles of machining and brazing. In this article, we characterize the RF properties of X-band klystron cavities and an integrated circuit manufactured with a novel additive manufacturing process. Parts are 3D printed in 316 L stainless steel with direct metal laser sintering, electroplated in copper, and brazed in one simple braze cycle. Stand-alone test cavities and integrated circuit cavities were measured throughout the manufacturing process. The un-tuned cavity frequency varies by less than 5% of the intended frequency, and Q factors reach above 1200. A tuning study was performed, and unoptimized tuning pins achieved a tuning range of 138 MHz without compromising Q. Klystron system performance was simulated with as-built cavity parameters and realistic tuning. Together, these results show promise that this process can be used to cheaply and quickly manufacture a new generation of highly integrated high power vacuum devices. Full article

The pursuit of reliable energy devices sealing solutions stands as a paramount engineering challenge for ensuring energy safety and dependability. This review focuses on an examination of recent scientific publications, primarily within the last decade, with a central aim to grasp and apply critical concepts relevant to the efficient design and specification of brazements for ceramic–metal active-brazed assemblies, emphasizing the sealing of energy devices. The goal is to establish robust and enduring joints capable of withstanding water-vapor and hydrogen environments. The review commences with a concise recapitulation of the fundamental principles of active brazing, followed by an in-depth exploration of material selection, illustrated using water-vapor-resistant sensors as illustrative examples. Furthermore, the review presents practical solutions for the sealing of energy devices while also scrutinizing the factors that exert significant influence on the deterioration of these active-brazed connections. Ultimately, the review culminates in a comprehensive discussion of emerging trends and developments in active brazing techniques for energy-related applications. Full article

A plate heat exchanger (PHE) is a modern, effective type of heat transfer equipment capable of increasing heat recuperation and energy efficiency. For PHEs, enhanced methods of heat transfer intensification can be further applied using the analysis and knowledge already available in the literature. A review of the main developments in the construction and exploration of PHEs and in the methods of heat transfer intensification is presented in this paper with an analysis of the main construction modifications, such as plate-and-frame, brazed and welded PHEs. The differences between these construction modifications and their influences on the thermal and hydraulic performance of PHEs are discussed. Most modern PHEs have plates with inclined corrugations on their surface that create a strong, rigid construction with multiple contact points between the plates. The methods of PHE exploration are mostly experimental studies and/or CFD modelling. The main corrugation parameters influencing PHE performance are the corrugation inclination angle in relation to the main flow direction and the corrugation aspect ratio. Optimisation of these parameters is one way to enhance PHE performance. Other methods of heat transfer enhancement, including improving the form of the plate corrugations, use of nanofluids and active methods, are considered. Future research directions are proposed, such as improving fundamental understanding, developing new corrugation shapes and optimisation methods and area and cost estimations. Full article

Explaining the wetting mechanism of Cu–P brazing materials and Cu remains challenging. This fundamental research aims to reveal the wettability mechanism of Si, Sn, and Zr doping on the interfacial bond strength of the Cu₃P/Cu system through the first principles study. We carried out several sets of calculations to test the validity of the result; included in the work are those used to establish the interfacial structure and to analyze the effect of doping on the wettability. Specific analysis was carried out in terms of three aspects: the work of adhesion ($W_{ad}$), the charge density difference, and the density of states (DOS). The calculated results show that doping with Si, Sn, and Zr elements can effectively improve the wettability within the CuP/Cu interface with very high accuracy, and is particularly effective when doped with Zr. These results provide an insightful theoretical guide for enhancing the CuP/Cu system’s wettability by adding active elements. Full article

In this article, the studies undertaken on brazed diamond tools were reviewed. The influences of the brazing alloys with different active elements on the brazing quality of brazed diamond tools are emphatically discussed. The differences in the micromorphology, friction and wear properties, and mechanical properties of brazed diamonds caused by three different brazing alloys are described in detail. The quality evaluation of brazed diamond tools is discussed from several aspects, such as the difference in microstructure of the diamond/brazing alloy interface, the friction and wear of brazed diamond tools, and the strength and residual stress of the brazing interface. Finally, relevant open questions related to the brazed diamond tools’ performance are outlined, and the future has been prospected. Full article

A systematic microstructural characterization of alumina joined to Hastelloy C22^® by means of a commercial active TiZrCuNi alloy, named BTi-5, as a filler metal is reviewed and discussed. The contact angles of the liquid BTi-5 alloy measured at 900°C for the two materials to be joined are 12° and 47° for alumina and Hastelloy C22^® after 5 min, respectively, thus demonstrating good wetting and adhesion at 900 °C with very little interfacial reactivity or interdiffusion. The thermomechanical stresses caused by the difference in the coefficient of thermal expansion (CTE) between the Hastelloy C22^® superalloy (≈15.3 × 10⁻⁶ K⁻¹) and its alumina counterpart (≈8 × 10⁻⁶ K⁻¹) were the key issues that had to be resolved to avoid failure in this joint. In this work, a circular configuration of the Hastelloy C22^®/alumina joint was specifically designed to produce a feedthrough for sodium-based liquid metal batteries operating at high temperatures (up to 600 °C). In this configuration, adhesion between the metal and ceramic components was enhanced after cooling by compressive forces created on the joined area due to the difference in CTE between the two materials. Full article

For the DEMO reactor, tungsten is considered as an armor material. Eurofer97 is planned to be used as a structural material for the first wall and in the divertor region, especially for the shielding liner component. To date, several joining solutions between W and Eurofer97 have been developed (copper brazing, W and Eurofer97 functional gradient material (FGM), etc.). Each existing joining solution has its own advantages (joining material, improved manufacturing process). In the present study, the choice of the joining material is driven, among other constraints, by a desire to minimize the thermal stresses at the materials’ interface. In this regard, FGM represents a promising solution. Another constraint that is taken into account in this study concerns the manufacturing process involved, which should be an improved industrial process. The present study proposes a joining solution, based on FGM, which, additionally to the advantages of the existing solutions, could reduce the long-term activation of the joining material. The development of a joining solution via Ti and Ta as materials constituting the FGM (Ti/Ta FGM) is presented in this paper. Due to the achieved density and the composition’s accuracy, the cold spray process is shown to be adapted for the Ti/Ta FGM’s manufacturing. Based on the feedback on the experience of joining between W, W/Cu FGM and CuCrZr, the final joining between W, Ti/Ta FGM and Eurofer97 is achieved using hot isostatic pressing, followed by a thermal treatment to recover Eurofer97’s mechanical properties, resulting in good joining quality. Full article

The problem of stainless steel brazing is still the focus of scientific research. In this work, the Mn-based brazing filler was used to braze 1Cr18Ni9Ti and 1Cr21Ni5Ti stainless steel. The typical microstructure of the 1Cr18Ni9Ti/1Cr21Ni5Ti joint was analyzed in detail, and the interface structure of the joint was determined to be 1Cr18Ni9Ti/Mn(s, s)/1Cr21Ni5Ti. The brazing temperature and holding time were shown to have a great influence on the microstructure of the brazed joint. The tensile strength of brazed joints first increased and then decreased with the rising of the brazing temperature and the holding time. The maximum tensile strength was 566 MPa when the joints were brazed at 1125 °C for 15 min. The diffusion of Mn and Cr was an important factor affecting the quality of the joints. The diffusion distances of Mn and Cr at different brazing temperatures and holding times were measured, and the diffusion activation energy and diffusion coefficient were achieved by the Arrhenius equation. Full article