Copper Brazing Research Articles

Effects of Cu Coating Addition on Mechanical Properties of Vacuum Brazed Joints

In this study, a copper brazing filler metal coating is fabricated on a 304 stainless steel (304SS) substrate using an electroplating technique. The effect of using electroplated copper brazing filler metal coatings compared to pure copper foil of the same thickness for vacuum brazing of stainless steel joints is investigated. The microstructure and microhardness of the brazed joints are characterized using X‐ray diffraction (XRD), scanning electron microscopy (SEM), and a Vickers hardness tester. The shear strength of the brazed joints is measured using an INSTRON 5869 universal testing machine. The results indicate that the electroplated Cu coating is dense, predominantly with a single cubic phase, with a few copper particles aggregating on the surface. Under electroplating conditions of 20 mA cm−2 for 1 h, the coating thickness was 56 μm. The shear strength of the brazed joint with this coating reached a maximum of 333.7 MPa, which is higher than that of a brazed joint with a 60 μm thick copper foil, which exhibits a shear strength of 303.2 MPa. The shear strength of the brazed joints shows an initial increase followed by a decrease as current density and electroplating time increase. This study provides significant technical support for brazing complex shapes or precision components. It suggests a method to simplify the brazing process, reduce production costs, and enhance the strength of brazed joints.

Exploring W-EUROFER brazed joints: S/TEM and nanoindentation analysis following post-brazing tempering treatment

Tempering treatments are essential for restoring the hardness and microstructure of EUROFER steel when W-EUROFER joints are formed at temperatures exceeding the steel's austenitization point (890 °C). This post-brazing heat treatment can, however, alter the microstructure and thereby affect the mechanical properties. This study explores the microstructural and nanomechanical effects in the brazed area of W-EUROFER joints following this heat treatment, utilizing copper as an intermediate filler material. Using Scanning Transmission Electron Microscopy (STEM) with Energy Dispersive Spectroscopy (EDS) on FIB lamellae and nanoindentation techniques we examined the stability and phase characteristics of the post-tempered microstructure in two lamellae that covers the whole phases of the braze microstructure.The tempering process enhances copper diffusion and the growth of copper precipitates without significantly altering the joint's overall microstructure. Despite the general stress-relief effects of tempering, which typically lower mechanical properties, the diffusion phases formed during brazing maintained high hardness and modulus, indicative of a complex, element-rich composition. A reduction in mechanical properties was observed in the iron-rich phase near the W-braze interface and the EUROFER base material, aligning with the purpose of the heat treatment. However, the copper braze and tungsten base material largely retained their stability and resilience to thermal treatments.This research provides vital insights into the behavior of these material systems under thermal processing, highlighting the necessity of optimizing heat treatment parameters to preserve joint integrity in high-performance applications such as nuclear fusion reactors. The findings contribute significantly to the development of durable and reliable materials for fusion energy, emphasizing the importance of controlled tempering processes to enhance material properties.

Effect of E-waste copper alloy additions on the microstructure and organization of Cu90PSn brazing joints.

The effects of different contents of e-waste alloy on the microstructure and joint properties of Cu90PSn brazing filler metal was investigated during copper and copper brazing. Microstructure of base metal and brazing filler metal was studied with scanning electronic microscopy (SEM). The properties of brazing joint obtained by adding different electronic waste filler metal for smelting copper alloy were compared together. The results indicated that the fluidity of Cu90PSn brazing filler metal was weakened and the spreading property of Cu90PSn brazing filler metal was damaged after the addition of e-waste copper alloy. The structure of Cu90PSn brazing filler metal is mainly composed of (Cu), Cu3P and (Cu,Sn) compounds. When a small amount of electronic waste copper alloy is added, a trace amount of Fe in the brazing filler metal is distributed in the matrix structure of the filler metal in the form of solid solution. With the increase of copper alloys contents by smelting e-waste, Fe content in Cu90PSn brazing filler metal increases; the granular Fe3P phosphide changes into lamellar form. The Cu3P compound phase changes from continuous large orderly arrangement to discontinuous small block structure. Therefore, adding a trace amount of electronic waste copper alloy to the solder induction brazing copper/copper can obtain a uniform composition of the brazing structure. And the welding performance is not affected. However, As the content of e-waste smelted copper alloy continues to increase, the tensile strength shows a downward trend, which is attributed to the presence of brittle compound Fe3P in the joint.

Wettability and microstructural evolution of copper filler in W and EUROFER brazed joints

In terms of wettability, active systems are characterized by a reduction in interfacial energy as the time at specific conditions is increased. This article aims to investigate the evolution of wettability and microstructure, which undergoes a critical transformation at temperatures and dwell times near brazing conditions due to their significant impact on resultant mechanical properties. The objective is to enhance wettability and prevent the formation of different phases that can occur rapidly within the brazing window conditions. Up to 1105 °C, complete fusion of the filler does not occur. However, once it happens, the expansion of the copper filler in EUROFER increases up to 400%, and the contact angle reduces from 100° to 10°, indicating an active wetting behavior. On the other hand, when copper is used with tungsten, an inert behavior is observed, maintaining the contact angle around 70°. Brazed joints carried out under the most promising wetting conditions demonstrated that at 1110 °C-1 min, various phenomena began to occur. This includes solid-state diffusion of copper in the EUROFER, following the austenitic grain boundaries, and partial dissolution of Fe in the copper braze. Increasing the brazing time from 2 to 5 min achieved high interfacial adhesion properties and controlled the diffusion layer and Fe-rich band formed at the W-braze interface, resulting in the best mechanical results (295 MPa).

Investigation of the Structure and Properties of Molybdenum Coatings Produced by Laser-Directed Energy Deposition

The paper considers the possibility of replacing the process of conventional vacuum brazing of a molybdenum plate on carbon steel using copper brazing with the process of laser-directed energy deposition of domestically produced molybdenum powder. The research task is motivated by the demand for removing low-melting copper brazing from molybdenum coatings on carbon steel. The parameters for the process of manufacturing molybdenum coatings using the additive technology of laser-directed energy deposition (LDED), which provides the required operational properties without further processing, have been developed. A study of the microstructure of the coating was carried out, including an examination of the distribution of the main elements over the depth of the coating. We established the preferred parameters of laser-directed energy deposition, which provide a high-quality deposited layer of Mo on the 25L carbon steel. The wear resistance of the coatings was examined following the «ball-on-disc» scheme according to the ASTM G99 standard. The results show that wear rate of the brazed Mo plate is higher than that of the deposited Mo layer on the 25L carbon steel substrate.

Design of higher temperature copper brazing filler metals with reduced brittle phase content

Anneal-resistant copper alloys have been developed to address the need for stronger yet lighter fin and tube parts in heat exchangers, in order to facilitate greater efficiency and increased temperature capability. As such, brazing as opposed to traditional soldering has become the preferred joining method for these materials, due to the enhanced high-temperature properties of such joints. Copper-based filler metals are used extensively for the brazing of these materials, generally based on the copper-phosphorus system with alloying additions. In the present study, the microstructural issues arising from the current commercially available filler metals are discussed and addressed through CALPHAD-supported alloy design. Three selected novel compositions were used in the brazing of pure copper as a test of the design concept. Alloy compositions in weight percent of Cu(bal.)− 7Ni-4Sn-5 P and Cu(bal.)-10Ni-2Sn-6.5 P were found to result in a reduction of brittle Cu3P phase while increasing the fraction (0.78 and 0.77 respectively) of copper-rich solid solution in joints post-braze, comparing favourably to commercial Meta-Braze™ 077 under similar conditions (0.61). Furthermore, the copper-rich solid solution was leaner in tin, predicted to impart an increased melting temperature while microhardness profiles indicate increased joint ductility. The implications for mechanical properties of filler metals in this alloy family are discussed.

Titanium and Tantalum Used as Functional Gradient Interlayer to Join Tungsten and Eurofer97

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.

Effect of Ni on grain boundary penetration in vacuum brazing of copper and stainless steel

Effect of Ni on grain boundary penetration in vacuum brazing of copper and stainless steel

Vacuum brazing of copper and SS316L using Ni–P eutectic alloy filler for nuclear applications

Vacuum brazing of copper and SS316L using Ni–P eutectic alloy filler for nuclear applications

Full-tungsten design and high heat flux test of ITER divertor Langmuir probe

A new design of the ITER divertor Langmuir probe (DLP), called “full-tungsten design”, has been proposed and analyzed. This new design addresses the poor thermal fatigue of the copper brazing layer of the previous DLP design. Tungsten is used as the heat shield material instead of the former copper alloy brazing layer in this full-tungsten design because of its relatively high strength, high melting point and good thermal conductivity. After structural optimization, the analysis results show good thermal and mechanical behavior, indicating the full-tungsten design is robust enough to satisfy ITER requirements. The R&D work of prototypes demonstrates the feasibility of manufacturing technology on machining complex tungsten components and tungsten-ceramic-tungsten brazing. In order to verify the design and brazing technology of DLP, high heat flux tests were undertaken using an electron beam device with an incident power of 15 MW/m2. The testing results show that the prototypes can survive under such harsh working conditions with the present structure and manufacturing technology.

Friction spot extrusion brazing of copper to AISI 304 stainless steel with Zn interlayer: effect of shoulder surface modification

Friction spot extrusion brazing of copper to AISI 304 stainless steel with Zn interlayer: effect of shoulder surface modification

Improvement for Ti3SiC2/Cu joint brazed using composite fillers with abnormal expansion ceramic particulates

AbstractReducing the residual stresses and improving the mechanical strength of large‐scale ceramic/metal brazing joints is an important problem that must be solved for its practical engineering application. Using composite filler with solid‐state phase transformation ceramic particulates, it is theoretically feasible to relieve the residual stress and improve the mechanical properties of ceramic/metal brazed joints. In this study, Cu mesh, Ag–28Cu–2Ti (wt.%), and yttria‐stabilized zirconia (0.6 mol.% YSZ solid‐state phase transformation ceramic particulates) composite power fillers were used in the brazing of Ti3SiC2 ceramic and pure copper. The microstructure of joints and YSZ particulates in the interface was investigated and confirmed by scanning electron microscopy (SEM), energy‐dispersive X‐ray spectroscopy (EDS), scanning transmission electron microscopy (STEM), and transmission electron microscopy (TEM). In addition, the effect of YSZ particulates content on the mechanical properties of joints was investigated and evaluated by the shear strength. The results show that the interfacial phases were mainly Ti5Si3, TiC, TixCu, Ag (s, s), Cu (s, s), and YSZ particulates. Moreover, most of YSZ particulates undergo the solid‐state phase transformation from tetragonal zirconia (t‐ZrO2) to monoclinic zirconia (m‐ZrO2) during the cooling process of brazing. The abnormal volume expansion of the solid‐state phase transformation reduced the thermal mismatch between Ti3SiC2 ceramic and filler, thereby reducing the residual stress in the interface of joint. When using composite filler with 6 wt.% YSZ particulates, the shear strength of Ti3SiC2/Cu joint reached the maximum. The maximum average shear strength of the joints was 80.2 MPa, which was about 103.6% more than the joint without YSZ particulates.

Design of Higher Temperature Copper Brazing Filler Metals with Reduced Brittle Phase Content

Design of Higher Temperature Copper Brazing Filler Metals with Reduced Brittle Phase Content

Design of Higher Temperature Copper Brazing Filler Metals with Reduced Brittle Phase Content

Design of Higher Temperature Copper Brazing Filler Metals with Reduced Brittle Phase Content

Effect of In and Pr on the Microstructure and Properties of Low-Silver Filler Metal

The novel low-silver 12AgCuZnSn filler metals containing In and Pr were used for flame brazing of copper and 304 stainless steel in this study. The effects of In and Pr content on the melting temperature, wettability, mechanical properties and microstructure of 12AgCuZnSn filler metal were analyzed. The results indicate that the solidus and liquidus temperatures of filler metals decrease with the addition of In. Trace amounts of Pr have little impact on the melting temperature of the low-silver filler metals. In addition, the spreading area of filler metals on copper and 304 stainless steel is improved. The highest shear strength of brazed joint is 427 MPa when the content of In and Pr are 2 wt.% and 0.15 wt.%, respectively. Moreover, it is observed that the trace amount of Pr significantly refines the microstructure of brazed joint matrix. A bright Pr3Cu4Sn4 phase is found in filler metal and brazing seam when the contents of In and Pr are 5 wt.% and 0.5 wt.%, respectively.

Active Brazing of Alumina and Copper with Multicomponent Ag-Cu-Sn-Zr-Ti Filler

The study was designed to investigate the synergic effect of Ti and Sn in the active metal brazing of Al2O3 ceramic to copper brazed, using the multicomponent Ag-Cu-Zr filler alloy. Numerous fine and hexagonal-shaped rod-like ternary intermetallic (Zr, Ti)5Sn3 phase (L/D = 5.1 ± 0.8, measured in microns) were found dispersed in the Ag-Cu matrix of Ag-18Cu-6Sn-3Zr-1Ti alloy, along with the ternary CuZrSn intermetallic phases. An approximate 15° reduction in contact angle and 3.1 °C reduction in melting point are observed upon the incorporation of Ti and Sn in Ag-18Cu-3Zr filler. Interestingly, the interface microstructure of Al2O3/Cu joints brazed by using Ag-18Cu-6Sn-3Zr-1Ti filler shows a double reaction layer: a discontinuous Ti-rich layer consisting of (Cu, Al)3(Ti, Zr)3O, TiO, and in-situ Cu-(Ti, Zr) precipitates on the Al2O3 side and continuous Zr-rich layer consisting of ZrO2 on the filler side. The shear strength achieved in Al2O3/Cu joints brazed with Ag-18Cu-6Sn-3Zr-1Ti filler is 31% higher, compared to the joints brazed with Ag-18Cu-6Sn-3Zr filler. Failure analysis reveals a composite fracture mode indicating a strong interface bonding in Al2O3/Ag-18Cu-6Sn-3Zr-1Ti filler/Cu joints. The findings will be helpful towards the development of high entropy brazing fillers in the future.

Simulation between Soldering and Brazing of Copper at 450 Temperature by Zn-Sn Fillet Alloy

In this research, a comparison between Soldering and Brazing welding of pure copper metal using a (Zn-Sn) alloy filler was numerically investigated. The welding operations on the eight pieces with dimension (30mm x 20mm x 2mm) were carried out used (Auto Desk Inventor program) to prepare four samples, while the simulation was conducted on these samples by utilized the (COMSOL Multiphysics 4.1 program) to investigate the heat distribution and tensile stress. The simulation study results showed that the thermal distribution of Soldering welding was less than that of the Brazing welding in the area between (40-60 mm) and the maximum temperature of Soldering welding in that region was (405 °C), while the highest temperature for the Brazing welding in the same area reaches to (449 °C). The total displacement of the Soldering welding was up to1.9 x10-7 mm greater than that of the Brazing welding when the shedding stress equal to 5x104 N/ m2

Investigation on the induction brazing of copper–steel tubes with different coil structures

The purpose of this study is to investigate the effect of coil structure on electromagnetic fields and temperature distributions of copper–steel tube induction brazing for compressor-automatic production line. To get a satisfied temperature distribution, five coil structures were designed and three-dimensional finite element models were established. The temperature distribution of the workpiece was numerically predicted and compared with the experimental values, and the simulated temperature field shows very good agreement with the experimental temperature measurements on the workpiece surface. The simulated results revealed that the coil structure was crucial and considerable to the thermal field of the workpiece and heating efficiency. Moreover, different materials have large differences in temperature change when heated by the same coil. To ensure good quality of the joints and high productivity, a reasonable heating time of rapid induction brazing was obtained at about 4 s. The comparison results indicated that the coil structure of square ring with series connection demonstrated the highest performance in terms of heating efficiency and energy usage among the coil designs.

The impact of brazing process on mechanical properties of S30408 stainless steel by experimental investigation

The stainless steel core-plate structure is a new prefabricated structure with the stainless steel core-plate as the major component. Studying the material characteristics of the stainless steel core-plate is the premise of structure design. The panels and the core tubes (thin-walled round stainless steel tube) are welded by the copper brazing, and the mechanical properties of material may be changed by this process. The tensile tests at room temperature, elevated temperatures and after fire exposure were carried out in this paper, and the results were compared with other tests. It was found that the yield strength of S30408 Stainless steel decreased to 64% of the raw material at room temperature due to the brazing process, and the ductility was slightly increased. The mechanical properties of the material after brazing process decreased more rapidly than other tests. The improved stress-strain relationship model at room temperature and elevated temperatures of the S30408 stainless steel after brazing process was proposed.

Developing a New Type of Jointing the Metal Plates of a Heat Exchanger

This paper proposes using a new composition of the metal polymer compound to joint heat exchanger plates. This composition makes it possible to improve the factors of plate junction, such as the cost, safety, efficiency, and rate of the junction procedure. We consider the benefits and drawbacks of the two main ways to joint metal plates of brazed steel plate heat exchangers (BPHE), namely, copper brazing and laser beam welding; propose to joint plates using a metal polymer compound consisting of the metal powder of steel 316L and binding agents; show the metal polymer compound production process; provide the results of the component mixing process depending on the parameters, such as duration and rate of mixing; as well as present the resulting density of the specimens made of the metal polymer compound, depending on the mixing conditions.