Brazing Time Research Articles

Brazing of Porous Nickel to Copper and Stainless Steel: Microstructure and Mechanical Properties

A porous nickel (Ni) was brazed to copper (Cu) and stainless steel 304 (SS304) using VZ2250 and MBF67 brazing filler metal with a composition of 77.4Cu-9.3Sn-7.0Ni-6.3P and 64.5Ni-25Cr-6P-1.5Si (Cu: Copper, Sn: Tin, Ni: Nickel, P: Phosphorus, Cr: Chromium, Si: Silicon), respectively for joint microstructure and mechanical properties analysis. Porous Ni with a pore density of 15 pores per inch (PPI) was sandwiched between Cu/VZ2250 and MBF67/SS304. A brazed joint of Cu/Porous Ni/SS304 with VZ2250 and MBF67 brazing filler metal was prepared in a high vacuum furnace at different brazing times of 5, 10, and 15 minutes for 1015 °C with a heating and cooling rate of 10 °C/min, respectively for comparison purpose. The microstructure and mechanical properties of the brazed joint were investigated to identify the joint ability after the brazing process. Scanning Electron Microscope (SEM) equipped with Energy Dispersive X-Ray Spectroscopy (EDS) confirmed the interfacial microstructure by the formation of the diffusion filler metal (dark grey colour) for the Cu/Porous Ni/SS304 with VZ2250 and MBF67 brazing filler metal. For shear strength tests, the value decreases with an increase in the brazing time. The shear strength tests for the brazed joint of Cu/Porous Ni/SS304 with VZ2250 and MBF67 brazing filler metal show the maximum shear strength test value can be achieved for the brazing time of 5 minutes. The decreasing shear strength value was observed with differences in structural data of porous Ni due to the softening after the brazing process. Keywords: Brazing, Microstructure, Porous Nickel, Shear Strength.

Acoustic cavitation-induced microstructure evolution in ultrasonically brazed Al/Cu joints using Zn-Al alloy fillers

Tailoring the phase constitutions of the interfacial reaction layers under the assistance of ultrasonic vibration is a convenient method to fabricate high-strength Al/Cu brazing joints. In this study, 1060-Al and T2-Cu dissimilar metals were ultrasonically brazed with Zn-3Al (wt. %) filler metals. Effects of ultrasonic brazing time on the microstructure and mechanical properties of joints were investigated. Results showed that the CuZn5 intermetallic compound (IMC) layer and Cu-based diffusion layer were created on the Cu substrate surface in the joint ultrasonically brazed at 400 ℃ for 2 s. However, the CuZn5 IMC layer was gradually transformed into a thin Al4.2Cu3.2Zn0.7 IMC layer by increasing the ultrasonic vibration time to 15 s. A well-matched coherent interface was formed between the Al4.2Cu3.2Zn0.7 ternary phase and the Cu-based diffusion layer. The phase transition of the Cu-side interfacial layer correlated closely with the acoustic cavitations induced super-saturation regions near the Cu substrate surface. The measured tensile strength of the Al/Zn-3Al/Cu joint ultrasonically brazed for 15 s was 89.3 MPa, which was approximately 2.5 times higher than that brazed for 2 s, and the tensile failure mainly occurred at the interface between the Al4.2Cu3.2Zn0.7 layer and the Cu-based diffusion layer.

Optimization of brazing parameters for 316L stainless steel with AgCuZn filler metal under argon atmosphere

This research studies the optimal parameters for brazing 316L stainless steel using AgCuZn as filler metal under an argon gas atmosphere. The brazing parameters included temperature, brazing time, and argon gas flow rate. The study employed Box-Behnken design for experimental design and desirability function as the optimization tool. Mechanical properties study included the measurements of shear force, microhardness, microstructure, and fracture of brazing joints through a scanning electron microscope (SEM) as well as the chemical composition using an energy dispersive x-ray spectroscopy (EDS). As a result, the temperature and the brazing time significantly affected the shear force of the brazed joint at a 95 percent confidence interval. The optimal condition of the study was 800°C of temperature and a 20-minutes brazing time which caused the maximum shear force at 5,909.1 N. The brazing joint strength was increased when the temperature and time of brazing were increased and reached the optimal point. Microstructure showed a formation of an Ag-rich phase, a Cu-rich equiaxed dendrite phase, and a eutectic Ag-rich phase, which completely combined as the network structure and evenly small fine grains. Moreover, the shear force of the brazed joint was decreased when the temperature and time of brazing exceeded the optimal point due to the grain growth of the interface layer.

Effect of Vacuum Brazing Conditions of Inconel 718 Superalloy Sheets on Microstructure and Mechanical Properties of Joints

Vacuum furnace brazing is one of the most commonly used joining processes in the aerospace industry, utilized in the manufacturing of the complex components of turbine jet engines, working in both their cold and hot sections. The modern aerospace industry demands continuous improvement of production processes to enhance the engine performance, while ensuring its reliability. Therefore, a better understanding of the processes that shape the properties of engine assemblies joints is crucial. This paper presents an analysis of the influence of key brazing process parameters – brazing time and gap width – on the microstructure and mechanical properties of Inconel 718 superalloy joints obtained with the Palnicro 36M filler alloy. The analysis was conducted basing on results from SEM/EDS analysis and peel, shear and spreadability tests.

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).

The effect of vacuum brazing time on the microstructure and mechanical properties of Ti-6Al-4 V to 316 L dissimilar joint using BNi-2 filler metal

Due to the distinct differences in physical and metallurgical properties, it is hard to join titanium alloys to stainless steels directly via conventional welding processes. In this research, the grade 5 titanium alloy was subjected to brazing with austenitic stainless steel through the vacuum furnace, and the process was conducted above the β transition temperature (BTT). In order to reduce brittle intermetallic formation, a nickel base filler metal (Ni-6.6Cr-4.5Si-3B) was employed under a vacuum condition, and the effect of time on the microstructure and mechanical properties of the joints was investigated. The brazing temperature led to the thickening of the interface to 400 µm, toward the titanium alloy, and the FeTi formed adjacent to the diffusion affected zone (DAZ). Moreover, the isothermal solidified zone (ISZ) widened during the whole process, which, led to higher dissolution of the titanium base metal in the ISZ. Because of the widening of the interfaces, there were no Ni-rich compounds or residual filler metal in this region. SEM result showed that TiB strengthening borides, which were distributed after 45 min, and this evolution caused an increase in the shear strength of the joint up to 67 MPa. Fractography analyses and XRD results of the fractured surfaces revealed that the Ti2Ni phase, which formed in the athermaly solidified zone (ASZ) during a two-step solidification reaction, caused the brittle fracture in all joints.

Comparative analysis of the brazing mechanism and wear characteristics of brazed diamond abrasive with Zr-alloyed Cu-based filler metals

In this work, Zr-alloyed (0 wt%, 0.5 wt%, 1.5 wt%, 2 wt%) Cu-based filler metals were successfully prepared for brazing diamond abrasive tools. The microstructure and brazing mechanism were investigated via scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD). The effects of brazing temperature and brazing time on the wear properties of diamond abrasive were investigated when the addition amount of Zr is 1 wt%. It found that, adding 1 wt% Zr, the microstructure of the filler metal alloy is uniformly refined and dense. The mechanical properties of the brazed diamond abrasives showed that the brazed Cu-based filler metal with 1 wt% Zr showed the best wear resistance, with the uneven and three-body wear rates reaching 18.8 % and 12.5 %. The findings from the various brazing processes indicated that the optimal grinding performance of the brazed joints was achieved at a brazing temperature of 940 °C and a holding time of 6 min. Under these conditions, the diamond dropout rate was measured at 6.3 %, while the rate of uneven wear reached 18.8 %.

Impacts of diffusion brazing time on mechanical properties of Nicrofer 5520 superalloy joint by Ni-15Cr-3.7B filler metal

Impacts of diffusion brazing time on mechanical properties of Nicrofer 5520 superalloy joint by Ni-15Cr-3.7B filler metal

Interfacial structure and strength of Al‐25Si‐4Mg‐1Cu joint brazed with Zn interlayer

AbstractA high‐quality joint of the parent metal Al‐25Si‐4Mg‐1Cu alloy (AlSi alloy) was brazed to itself using Zn layer as a filler material. The typical microstructure of AlSi/Zn/AlSi joint was Al‐Zn solid solution, primary Si phase and α‐Al phase. When brazing temperature was increased from 400 to 405°C, Zn began to melt and reacted with Al diffused from base material, then Si phase formed. While the increase in brazing temperature to 415°C caused the gradual buring of Zn from Al‐Zn solid solution, and α‐Al remained. Furthermore, the shear strength of the joint increased because of α‐Al phase and Si phase formation. In addition, with brazing time extending from 8 to 12 min, the amount of Al‐Zn solid solution decreased, while the amount of Si phase and α‐Al phase increased, thus the shear strength of the joint was improved. While the increase in holding time extending to 14 min caused many micro‐voids formed, and the shear strength of the joint was reduced. Finally, the shear strength of the joint brazed at 415°C for 12 min reached 65.6 MPa.

Effect of diffusion brazing time on microstructure, isothermal solidification completion and microhardness distribution during joining of Nicrofer 5520 superalloy using a liquated Ni–Cr–B interlayer

In the present study, the effect of time on the microstructural evolution, distribution of elements, type of precipitated phases, and microhardness of diffusion brazed Nicrofer 5520 superalloy using a BNi-9 (Ni–15%Cr–3.7%B) interlayer was investigated. The diffusion brazing was carried out at 1120 °C for seven different holding times by using a 38 μm thick interlayer. The results indicated that the holding time of 30 min was sufficient for complete isothermal solidification. The eutectic gamma solid solution, Ni-rich borides, and Cr–Mo-rich borides were identified near the bond center before the completion of isothermal solidification, (Ni, Mo, Cr)-rich borides and Cr–Ni–Mo–Fe carbides with different morphologies were found in the diffusion affected zone (DAZ). In the holding time longer than 30 min and, the volume fraction of the precipitated phases in the DAZ decreased, and they transformed into rounder particles. Accordingly, the chemical composition of the interlayer became more homogeneous, resulting in a lower DAZ phases’ density that is happened over the higher brazing times. As the holding time was increased, the chemical composition in the interlayer became more similar to the base metal, and the microhardness in the bond zone and its surrounding became more uniform.

Microstructure coarsening in Ba0.5Sr0.5Co0.8Fe0.2O3-δ during reactive air brazing

Reactive air brazing of the ceramic oxygen transport membrane material BSCF causes microstructural modifications. The trend towards minimizing of membrane thicknesses requires a physical understanding of these modifications since they may influence both oxygen permeation and mechanical properties. To this purpose, wetting samples with variations in the Ag-xCuO braze alloy (1 < x < 25 at.-%) and the brazing time (0 < t < 120 min) were characterized by quantitative image analysis. We found that the pore size in reactive air brazed BSCF increases with increased brazing time as well as CuO-content in the braze. A local porosity minimum is always observed at the end of the reaction zone close to the unaffected bulk BSCF. Additionally, a zone with unidirectionally elongated grains at the end of which silver residues were found is observed. The observed coarsening effects are explained by liquid melt film penetration along the grain boundaries which increases the grain boundary mobility. Phase field simulations qualitatively confirmed the experimentally observed elongated grain structure.

Optimization of Vacuum Brazing Process Parameters in Ti-6Al-4V Alloy

In this study, the optimal parameters of the vacuum brazing titanium alloy Ti-6Al-4V with TiCuNi filler (30 μm-thick metal foil) were investigated by the Taguchi method. The microstructures, microhardness, and fractographs of the titanium brazed joints produced by these optimal parameters were also analyzed. The results of this study demonstrate that for the best tensile strength, the optimal combination of process parameters is: 890 °C soaking temperature, 60 min soaking time, 975 °C brazing temperature, and 45 min brazing time. The tensile strength obtained by welding with the optimal parameters was found to be 1265 MPa. A small error of 0.24% between experimental and predicted values confirmed the validity of the combined optimized parameters. Finally, from the means of variance analysis (ANOVA), out of the four factors, the highest contribution to the optimal parameters was found to be the brazing time, accounting for 47.3%. The base material of vacuum brazing (VB) weldment is mainly composed of white granular α titanium, slender β titanium, and layered structures that are interlaced by α and β. The weld bead, composed of Ti-15Cu-15Ni, contains many slender needle-shaped Widmanstätten structures. This structure is associated with higher strength and lower ductility. The weld bead hardness of the vacuum brazed parts is higher than that of laser beam weldment and gas tungsten arc weldment. This study demonstrates the feasibility of the Taguchi method for obtaining the optimal process parameters of titanium vacuum brazed joints.

Microstructure and joint properties of high-nitrogen steel brazed by AgCuNi filler metal

In this paper, high-nitrogen steel (HNS) was joined by vacuum brazing using an Ag–Cu–Ni filler metal and the effect of brazing temperature and duration time on the evolution of mechanical properties and microstructure of HNS joints were analyzed. The results showed that the optimal brazing temperature was 950[Formula: see text]C and the optimal shear strength was obtained with the value of 212.4 MPa when the brazing temperature was 950[Formula: see text]C with the brazing time of 10 min.

Interfacial microstructures and Grinding performance of Synthetic Diamond Grits brazed by Cu-22Sn-3Cr Alloy

To ensure the reliable bonding and low thermal damage of brazed diamond grits, a Ni-free Cu-Sn-Cr filler alloy was developed based on our previous study. Interfacial microstructure of diamond grits brazing used by Cu-22Sn-3Cr (in wt. %) filler alloy at 950 °C for 5, 10, 20, and 40 min were systematically investigated. Only Cr7C3 was generated at the interface between diamond and Cu-22Sn-3Cr alloy, and the thickness of Cr7C3 was increased after extended brazing time. The grinding performance of diamond tools brazed using Cu-22Sn-3Cr alloy has fewer ratios of diamond grits with breakage and fall-off failures and thus was found to be superior to that brazed by Ni-14Cr-10P filler alloy. In addition, alloy composition has a more significant influence than brazing time on the interfacial microstructure and mechanical behavior of brazed diamond grits; and the higher mechanical behavior of diamond grits brazed using Cu-Sn-Cr filler alloy is proved to be closely related to the low solubility of C in Cu-Sn-based alloy. Results obtained in this work are also crucial for developing a diamond brazing technique to fabricate diamond-related materials and devices.

Ultrasonic brazing of Zr-based bulk metallic glass and 1060 Al alloy using Zn-3Al filler metal

Ultrasonic brazing of Zr-based bulk metallic glasses (Zr-BMG) and 1060-Al alloy dissimilar was realized by using a Zn-3Al filler metal. A firm metallurgical bonding was obtained at the dissimilar joint interfaces. In the initial stage, a single-phased Zn50Al25Zr25 IMC layer was found on the Zr-BMG surface. Prolonging the brazing time, the excessive growth of the Zn50Al25Zr25 IMC layer inhibited the diffusion of Al from brazing seam to the reaction front, which induced the composition fluctuation of Al and thus the formation of Zn50Al25Zr25/Zn-rich phase composite layers on the Zr-BMG surface. The shear strength of joints was affected by the interfacial reaction phase, and the highest value obtained was 68 MPa.

Brazing of Porous Copper Foam with Copper Sheet Using CuNiSnP Amorphous Filler Metal

This research studies effects of the brazing time on interfacial microstructure of brazed joint between the porous copper foam (PCF) and Cu substrate using CuNiSnP amorphous filler metal. To examine the interfacial microstructure and its properties, an assessment of PCF/CuNiSnP/Cu brazed joints was conducted after electric furnace brazing under hydrogen (H2) atmosphere. The results showed that the interfacial microstructure was thick for short brazing time specimens and thin for prolonged brazing time specimens. The interfacial microstructures consisted of Cu-rich solid solution, (Cu, Ni)3P, and Cu3P as a eutectic structure discovered in the brazing region at different brazing times of 5, 10, and 20 min. Only the Cu-rich solid solution and (Cu, Ni)3P were found in the specimen with brazing time of 30 min. indicating that different brazing times affected interfacial microstructures and therefore reliability of the brazed joints.

Dissimilar Brazing of Ti-15Mo-5Zr-3Al and Commercially Pure Titanium Using Ti-Cu-Ni Foil.

Dissimilar brazing of Ti–15Mo–5Zr–3Al (Ti-1553) to commercially pure titanium (CP-Ti) using Ti–15Cu–15Ni foil was performed in this work. The microstructures in different sites of the brazed joint showed distinct morphologies, which resulted from the distributions of Mo, Cu, and Ni. In the brazed zone adhered to the Ti-1553 substrate, the partitioning of Mo from the Ti-1553 into the molten braze caused the formation of stabilized β-Ti without Ti2Cu/Ti2Ni precipitates. In the CP-Ti side, the brazed joint displayed a predominantly lamellar structure, composed of the elongated primary α-Ti and β-transformed eutectoid. The decrease in the Mo concentration in the brazed zone caused the eutectoid transformation of β-Ti to Ti2Cu + α-Ti in that zone. The diffusion of Cu and Ni from the molten braze into the CP-Ti accounted for the precipitation of Ti2Cu/Ti2Ni in the transformed zone therein. The variation in the shear strength of the joints was related to the amount and distribution of brittle Ti2Ni compounds. Prolonging the brazing time, the wider transformed zone, consisting of coarse elongated CP-Ti interspersed with sparse Ti2Ni precipitates, was responsible for the improved shear strength of the joint.

Effect of brazing parameters on microstructure and mechanical properties of TMC/Si3N4 joint

A multilayered filler made up of Cu foam and Ag-28Cu foils was used to successfully braze (TiB+Y2O3)/titanium matrix composites (TMC) and silicon nitride ceramics (Si3N4). The microstructure of the TMC/Si3N4 joints obtained at different brazing parameters was investigated. The results showed the interfacial structure of the joints is composed of TiCu, TiCu2, Ag (s, s), Cu (s, s), TiN and Ti5Si3 phases. The growth equation of the TiN layer was established and its thickness was increased with respect to the brazing time and brazing temperature. Optimal shear strength of approximately 180 MPa was achieved when the joint was brazed for 10 min.

Vacuum brazing of Al2O3 and 3D printed Ti6Al4V lap-joints using high entropy driven AlZnCuFeSi filler

In this work, we studied the brazing characteristics of Al2O3 and 3D printed Ti–6Al–4V alloys using a novel equiatomic AlZnCuFeSi high entropy alloy filler (HEAF). The HEAF was prepared by mechanical alloying of the constituent powder and spark plasma sintering (SPS) approach. The filler microstructure, wettability and melting point were investigated. The mechanical and joint strength properties were also evaluated. The results showed that the developed AlZnCuFeSi HEAF consists of a dual phase (Cu–Zn, face-centered cubic (FCC)) and Al–Fe–Si rich (base centered cubic, BCC) phases. The phase structure of the (Cu–Al + Ti–Fe–Si)/solid solution promises a robust joint between Al2O3 and Ti–6Al–4V. In addition, the joint interfacial reaction was found to be modulated by the brazing temperature and time because of the altered activity of Ti and Zn. The optimum shear strength reached 84 MPa when the joint was brazed at 1050 °C for 60 s. The results can be promising for the integration of completely different materials using the entropy driven fillers developed in this study.

Microstructure and Mechanical Properties of Commercially Pure Ti/Steel Joint Brazed by Zr-Ti-Ni Amorphous Filler Metal.

In this study, the characteristics of commercially pure titanium (hereinafter referred as CP-Ti)/Steel joints, brazed with Zr-Ti-Ni amorphous filler metal were analyzed. The effects of brazing temperature and time on the microstructure and joining strength of the CP-Ti/Steel joints were investigated. It was observed that Ti diffused into stainless steel substrate formed a brittle reaction zone, which contained intermetallic compounds, such as τ (Ti5Cr7Fe17), (Fe, -Ni)Ti, and FeTi, observed at the joint interface. As the brazing temperature and time increased, the width of the reaction layer in the joint was observed to increase. To suppress the oxidation of the substrates, the experiment was conducted at a cooling and heating speed of 100 °C/min, under a vacuum of 5×10-5 torr. The joining strength was observed to be significantly affected by the brazing conditions, such as temperature and duration time. The shear strength test showed that the strength increased for 15 min and then sharply decreased. This was attributed to the formation of brittle intermetallic compounds, like (Fe, Ni)Ti. The joint brazed at 880 °C for 15 min showed the maximum joining strength, of 216 MPa.