Diffusion-bonded Joints Research Articles

The Interfacial Microstructure and Mechanical Properties of Diffusion-Bonded Joints of 316L Stainless Steel and the 4J29 Kovar Alloy Using Nickel as an Interlayer

316L stainless steel (Fe–18Cr–11Ni) and a Kovar (Fe–29Ni–17Co or 4J29) alloy were diffusion-bonded via vacuum hot-pressing in a temperature range of 850–950 °C with an interval of 50 °C for 120 min and at 900 °C for 180 and 240 min, under a pressure of 34.66 MPa. Interfacial microstructures of diffusion-bonded joints were characterized by optical microscopy (OM), scanning electron microscopy (SEM), X-ray diffraction (XRD), and energy dispersive spectroscopy (EDS). The inter-diffusion of the elements across the diffusion interface was revealed via electron probe microanalysis (EPMA). The mechanical properties of the joints were investigated via micro Vickers hardness and tensile strength. The results show that an Ni interlayer can serve as an effective diffusion barrier for the bonding of 316L stainless steel and the 4J29 Kovar alloy. The composition of the joints was 316L/Ni s.s (Fe–Cr–Ni)/remnant Ni/Ni s.s (Fe–Co–Ni)/4J29. The highest tensile strength of 504.91 MPa with an elongation of 38.75% was obtained at 900 °C for 240 min. After the width of nickel solid solution (Fe–Co–Ni) sufficiently increased, failure located at the 4J29 side and the fracture surface indicated a ductile nature.

Effect of bonding pressure on microstructure and mechanical properties of Ti-6Al-4V diffusion-bonded joint

In this study, solid-state diffusion bonding of Ti-6Al-4V alloy using a pure copper interlayer was conducted, and the effect of bonding pressure (0.5 to 4 MPa) on microstructure and mechanical properties was investigated. The joint zones were analyzed by optical microscope (OM) and scanning electron microscope (SEM), and microhardness and shear strength tests were also employed to evaluate mechanical behaviors of the joints. The results showed that diffusion of Cu into the Ti alloy led to the formation and the stability of β-Ti as a strengthening phase in the joint zone. Moreover, the increase in bonding pressure made the joint width be decreased to the minimum value. The maximum shear strength of 571 MPa was achieved for the bond made with 4 MPa bonding pressure, whereas with a decrease in pressure, the shear strength fell to 358 MPa that could be attributed to the increase in the joint width and the formation of brittle intermetallic compounds at the interface.

Design, development and qualification of a titanium to SS joint with groove

An improved lap type diffusion-bonded transition joint was developed between titanium (Ti) pipe and stainless steel (SS) pipe with grooves at the interface for use in high pressure-high temperature applications. The groove design was optimised using finite element method (FEM) so as to produce joint strength superior to the strength of the Ti pipe being joined. Elastic-plastic FE analyses were performed simulating large displacement and deformation involved. Further, joints were subjected to a simplified pull-out test to assess its strength. A good matching of joint strength, within 10% of FEM prediction and experimental results has been achieved. Design curves were generated using non dimensional parameters like r/t and a1/t (r-pipe radius, t- pipe thickness and a1-groove depth) to arrive at the groove depth for r/t range of 10, 15 and 20. It was demonstrated experimentally that the joint with groove performs better under thermal cycling loads. [Received 12 March 2016; Accepted 27 October 2016]

Effect of Bonding Temperature on Phase Transformation of Diffusion-Bonded Joints of Duplex Stainless Steel and Ti-6Al-4V Using Nickel and Copper as Composite Intermediate Metals

In the present study, the effect of bonding temperature on phase transformation of diffusion-bonded joints of duplex stainless steel (DSS) and Ti-6Al-4V (Ti64) using simultaneously both nickel (Ni) and copper (Cu) interlayers was investigated in the temperature range of 1148 K to 1223 K (875 °C to 950 °C) insteps of 25 K (25 °C) for 60 minutes under 4 MPa uniaxial pressure in vacuum. Interfaces were characterized by scanning electron microscopy and interdiffusion of the chemical species across the diffusion interfaces were witnessed by electron probe microanalysis. At 1148 K (875 °C), layer-wise Cu4Ti, Cu2Ti, Cu4Ti3, CuTi, and CuTi2 phases were observed at the Cu-Ti64 interface; however, DSS-Ni and Ni-Cu interfaces were free from any intermetallic. At 1173 K and 1198 K (900 °C and 925 °C), Cu interlayer could not restrict the diffusion of atoms from Ti64 to Ni, and vice versa; and Ni–Ti-based intermetallics were formed at the Ni-Cu interface and throughout the Cu zone as well; however, at 1223 K (950 °C), both Ni and Cu interlayers could not inhibit the diffusion of atoms from Ti64 to DSS, and vice versa. The maximum shear strength of ~377 MPa was obtained for the diffusion couple processed at 1148 K (875 °C) and strength of the bonded joints gradually decreased with the increasing bonding temperature due to the widening of brittle intermetallics at the diffusion zone. Fracture path indicated that failure took place through the Cu4Ti intermetallic at the Cu-Ti64 interface when bonding was processed at 1148 K (875 °C). When bonding was processed at 1173 K and 1198 K (900 °C and 925 °C), fracture took place through the Ni3Ti intermetallic at the Ni-(Ni + Cu + Ti64 diffusion reaction) interface; however, at 1223 K (950 °C), fracture morphology indicated the brittle nature and the fracture took place apparently through the σ phase at the DSS-(DSS + Ni + Cu + Ti64 diffusion reaction) interface.

Characterization of diffusion-bonded joint between Al and Mg using a Ni interlayer

Aluminum and magnesium were joined through diffusion bonding using Ni interlayer. The microstructure and mechanical performance of the Al/Ni/Mg joints at different temperatures was investigated by means of scanning electron microscope (SEM), electro-probe microanalyzer (EPMA), X-ray diffraction (XRD), Vickers hardness testing, and shear testing. The results show that the addition of Ni interlayer eliminates the formation of Mg–Al intermetallic compounds and improves the bonding strength of the Al/Mg joints. The Al/Ni/Mg joints are formed by the diffusion of Al, Ni and Mg, Ni. The microstructure at the joint interface from Al side to Mg side is Al substrate/Al–Ni reaction layer/Ni interlayer/Mg–Ni reaction layer/Mg substrate multilayer structure. The microhardness of the Mg–Ni reaction layer has the largest value of HV 255.0 owing to the existence of Mg2Ni phase. With the increase of bonding temperature, the shear strength of the joints increases firstly and then decreases. The Al/Ni/Mg joint bonds at 713 K for 90 min, exhibiting the maximum shear strength of 20.5 MPa, which is greater than that of bonding joint bonded directly or with Ag interlayer. The fracture of the joints takes place at the Mg–Ni interface rather than the Al–Ni interface, and the fracture way of the joints is brittle fracture.

Microstructure and Properties of AZ31B Magnesium-LY12 Aluminum Alloys Diffusion-Bonded Joint

In this paper, AZ31B magnesium alloy/LY12 aluminum alloy were bonded together with copper foil as interlayer by vaeuum diffusion bonding technology at different temperature for holding time 60 min and pressure 2.5MPa. Analysis the microstructure of the joint under the condition of 450°C,and the effects of heating temperature on the shear thrength , microhardness and the width of the interface zone were studied. The results showed that under the condition of 450°C in holding time 60 min and pressure 2.5MPa, the microstructure at interface zone of diffusion brazing joint includes α-Mg solid solution, Mg2Cu, Cu2Mg, γ-Cu solid solution, CuAl, CuAl2 and β-Al solid solution. The width of the interface increases with brazing temperature increasing, and the microhardness gradient of interface zone in the side of aluminum alloy is much higher than that in magnesium alloy side. As the welding temperature increases, the shear strength shows an increasing trend at first and then decreases. When the welding process is 460°C keeping for 60 min, welding pressure is 2.5Mpa, the highest shearing strength of the joint can reach 35 MPa.

Microstructural characterization of a diffusion-bonded joint for 9Cr-ODS and JLF-1 reduced activation ferritic/martensitic steels

Bonding of oxide dispersion strengthened (ODS) steels to non-ODS reduced activation ferritic/martensitic (RAFM) steels is essential to their application to blanket systems. In the present study, a diffusion-bonded joint of the candidate 9Cr-ODS steel and JLF-1 RAFM steel was fabricated using hot isostatic pressing (HIP). The effect of post-bond heat treatments (PBHTs) was studied by hardness measurement and microstructural analysis. The results indicated that, after normalization and tempering (N&T), the hardness and microstructures of 9Cr-ODS and JLF-1 base metals recovered to levels similar to those before HIP. However, a soft region was observed across the bonding interfaces for all specimens containing the as-HIPed condition and those after PBHTs. This was due to coarser micro-carbides (M3C in as-HIPed condition and M23C6 in N&T conditions) near the interfaces than in the base metals for both 9Cr-ODS and JLF-1. Energy Dispersive X-ray Spectroscopy (EDS) analysis confirmed that carbon, tungsten, and chromium in the matrix near the interfaces are transferred to the micro-carbides, making them coarser there. Ti diffused from the 9Cr-ODS side to the JLF-1 side forming Ti-rich carbides after tempering, especially at high temperature to 1073K.

Effect of Bonding Time on Interfacial Reaction and Mechanical Properties of Diffusion-Bonded Joint Between Ti-6Al-4V and 304 Stainless Steel Using Nickel as an Intermediate Material

In the current study, solid-state diffusion bonding between Ti-6Al-4V (TiA) and 304 stainless steel (SS) using pure nickel (Ni) of 200-μm thickness as an intermediate material was carried out in vacuum. Uniaxial compressive pressure and temperature were kept at 4 MPa and 1023 K (750 °C), respectively, and the bonding time was varied from 30 to 120 minutes in steps of 15 minutes. Scanning electron microscopy images, in backscattered electron mode, revealed the layerwise Ti-Ni-based intermetallics like either Ni3Ti or both Ni3Ti and NiTi at titanium alloy-nickel (TiA/Ni) interface, whereas nickel-stainless steel (Ni/SS) interface was free from intermetallic phases for all the joints. Chemical composition of the reaction layers was determined by energy dispersive spectroscopy (SEM–EDS) and confirmed by X-ray diffraction study. Maximum tensile strength of ~382 MPa along with ~3.7 pct ductility was observed for the joints processed for 60 minutes. It was found that the extent of diffusion zone at Ni/SS interface was greater than that of TiA/Ni interface. From the microhardness profile, fractured surfaces, and fracture path, it was demonstrated that the failure of the joints was initiated and propagated apparently at TiA/Ni interface near Ni3Ti intermetallic for bonding time less than 90 minutes, and through Ni for bonding time 90 minutes and greater.

Effect of Bonding Temperature on Interfacial Reaction and Mechanical Properties of Diffusion-Bonded Joint Between Ti-6Al-4V and 304 Stainless Steel Using Nickel as an Intermediate Material

Effect of Bonding Temperature on Interfacial Reaction and Mechanical Properties of Diffusion-Bonded Joint Between Ti-6Al-4V and 304 Stainless Steel Using Nickel as an Intermediate Material

Transition Analysis to Study the Effect of Cooling Rates on Thermal Stresses for Diffusion Bonded Joints

In this work the analytical and numerical methods were used to calculate the residual stresses induced in the joint due to the deference in the physical and mechanical properties of the materials, cooling from bonding temperature to room temperature. The residual stresses induced in graphite may be become too high that the joint break down so it takes as major stress in the joint. It was found that the residual stress is affected by the joint geometry and the nickel interlayer thickness. The analytical calculation of the residual thermal stresses in graphite/Inconel 600 and Inconel 600/nickel interlayer/Graphite multilayered was done for bonding temperature Tbond=800 o Cwith various nickel foil thickness, it found that increasing nickel thickness reduce the thermal residual stresses inside the graphite. Numerical method by FEM was used to estimate the distribution of the maximum residual stresses (first principle stress) in the joint. The results indicate that increasing nickel thickness reduces the maximum tensile residual stress. So the joint thicknesses with graphite (5 mm) /Ni (0.1-0.2)mm/ Inconel600 (5 mm) are convenient.

Microstructure and Corrosion Aspects of Dissimilar Joints of Zircaloy-4 and 304L Stainless Steel

In this study, diffusion bonding is used to join rods of Zircaloy-4 with stainless steel 304L. The microstructure of the interface of the dissimilar joints was characterized by SEM-EDS and x-ray diffraction (XRD). It consists of three distinct layers, each separately localized in the modified stainless steel and Zircaloy-4 (Zy-4) matrix. The XRD patterns indicate the presence of intermetallics in the diffusion-bonded joints. Joint corrosion was evaluated by potentiodynamic polarization and some aspects were discussed according to the mixed potential theory. The corrosion results indicate the presence of a local galvanic effect. SEM examination of the corroded joints indicates preferential corrosion around the Zy-4/SS304L interface, probably due to residual stresses and the intermetallic compounds generated during diffusion bonding process at high temperature.

Investigation of the transition zone of diffusion-bonded joints between bronze BrKh08 and copper M1

The results of investigations of the transition zone between BrKh08 bronze and copper M1 produced by a diffusion bonding through a nickel–phosphorus interlayer are used to evaluate the quality of the diffusion-bonded joints, to determine the dependence of the distribution of elements in the diffusion zone and also to calculate the coefficient of mutual diffusion of copper and nickel and construct the dependence of the properties on concentration.

Effect of phase transformation and intermetallic compounds on the microstructure and tensile strength properties of diffusion-bonded joints between Ti–6Al–4V and AISI 304L

The occurrence of a phase transformation and the effect of intermetallic compounds on the microstructure and tensile strength properties of diffusion-bonded (DB) joints between Ti–6Al–4V and AISI 304L were studied in the temperature range of 875–950°C with an interval of 25°C, a bonding time of 60min and pressures of 4MPa and 8MPa. A maximum tensile strength of 242.6MPa, was observed for diffusion-bonded joints that were processed at a temperature of 900°C, bonded for 60min at a pressure of 4MPa and annealed for 2h at 750°C. Optical microscopy and scanning electron microscopy (SEM) were used to examine the grain growth and the fine details of the interface structure. Energy dispersive X-ray analysis (EDAX) and X-ray diffraction analysis (XRD) revealed the existence of intermetallic compounds and corroborated the phase transformation.

Microstructure and mechanical property evaluation of diffusion-bonded joints made between SAE 2205 steel and AISI 1035 steel

Microstructural and mechanical property evaluation of the joint region of direct diffusion-bonded joints made between duplex stainless steel SAE 2205 and medium-carbon steel AISI 1035 was studied for the samples processed at temperatures of 850, 900, 950 and 975°C, with holding time of 60 and 90-min and pressures of 20 and 30MPa. The energy dispersive X-ray analysis (EDAX) and X-ray diffraction analysis (XRD) confirmed the presence of interfacial reaction products, such as sigma phase and intermetallics at the interface. The shear strength of the samples processed at 975°C for 90min and at a pressure of 20MPa was 360.9MPa. Interestingly, the capability of the joint strength was not reduced as the result of formation of hard intermetallics because of diffusive and interfacial reactions.

Phase and morphology evolution in high-temperature Ti 3SiC 2–NiTi diffusion-bonded joints

Diffusion joints were formed between Ti3SiC2 and equiatomic NiTi at different temperatures. Homogeneous diffusion bonding was observed at 1100 and 1200 °C, while no bonding was evident at 1000 °C and the samples were completely reacted at 1300 °C. Si diffusion from Ti3SiC2 into NiTi was the main mechanism responsible for the phase and morphology evolution at the interface. In contrast to the 1100 °C experiments, the liquid-phase diffusion at 1200 °C significantly increased the Si diffusion, and changed the phase morphology.

210303 硬脆性材料拡散接合部の微細組織変態を利用した靱性改善(OS15 生産加工3,オーガナイズド・セッション)

210303 硬脆性材料拡散接合部の微細組織変態を利用した靱性改善(OS15 生産加工3,オーガナイズド・セッション)

Investigation of intergranular corrosion of 316L stainless steel diffusion bonded joint by electrochemical potentiokinetic reactivation

Electrochemical potentiokinetic reactivation technique (EPR) was employed to assess degree of sensitization in 316L stainless steel diffusion bonded joint (DBJ). The result showed the degree of sensitization of DBJ was much smaller than that of base material (BM). No chromium carbides precipitated at grain boundaries in DBJ after 100 h treatment at 650 °C, while chromium carbides could be seen clearly in the BM after 8 h treatment, indicating that DBJ has better intergranular corrosion resistance than BM. Diffusion bonding technique will not increase intergranular corrosion susceptibility of 316L DBJ. Reactivation potential has the biggest effect on sensitization.

Diffusion bonding of 410 stainless steel to copper using a nickel interlayer

Abstract In the present work, plates of stainless steel (grade 410) were joined to copper ones through a diffusion bonding process using a nickel interlayer at a temperature range of 800–950 °C. The bonding was performed through pressing the specimens under a 12-MPa compression load and a vacuum of 10 − 4 torr for 60 min. The results indicated the formation of distinct diffusion zones at both Cu/Ni and Ni/SS interfaces during the diffusion bonding process. The thickness of the reaction layer in both interfaces was increased by raising the processing temperature. The phase constitutions and their related microstructure at the Cu/Ni and Ni/SS diffusion bonding interfaces were studied using optical microscopy, scanning electron microscopy, X-ray diffraction and elemental analyses through energy dispersive spectrometry. The resulted penetration profiles were examined using a calibrated electron probe micro-analyzer. The diffusion transition regions near the Cu/Ni and Ni/SS interfaces consist of a complete solid solution zone and of various phases based on (Fe, Ni), (Fe, Cr, Ni) and (Fe, Cr) chemical systems, respectively. The diffusion-bonded joint processed at 900 °C showed the maximum shear strength of about 145 MPa. The maximum hardness was obtained at the SS–Ni interface with a value of about 432 HV.

Microstructure and mechanical properties of Ti6Al4V/Cu-10Sn bronze diffusion-bonded joint

The microstructures and mechanical properties of Ti6Al4V/Cu-10Sn bronze diffusion-bonded joint were studied via scanning electron microscopy(SEM) and energy dispersive spectrometry(EDS). Diffusion bonding of Ti6Al4V to Cu-10Sn bronze was investigated at different holding time. Four obvious interfacial layers were observed in the joint. It is revealed that the bonding joint has high shear strength up to 102 MPa bonded at 830 °C, bonding pressure 10 MPa and bonding time 15 min. Shear test results show that the fracture takes place between the reaction layer and the Cu-10Sn bronze substrate, and the shear strength is strongly related to the formation of Cu-Ti-Sn intermetallic compounds.

Effects of Carbon Content on Intermetallic Compound Layer and Joint Strength in Friction Welding of Al Alloy to Steel

The microstructure and bond strength of the friction-welded interface of Al-Mg alloy A5052 to carbon steel S45C have been investigated, to establish their dependence on C content of steel by comparison with those observed in the joint of A5052 alloy to low C steel S10C. TEM observations revealed that an intermetallic compound layer 100–1 000 nm thick was formed at the interface, consisting of Fe2Al5 and Fe4Al13, similar to that observed at the A5052/S10C interface. The thickness of the intermetallic compound layer was increased almost in proportion to friction time in both joints, while that of the A5052/S45C joint grew at a lower rate than that of the A5052/S10C joint. In the intermetallic compound layer, granular Fe2Al5 and Fe4Al13 were distributed almost randomly, in contrast to those observed at the interface of the diffusion couple or diffusion-bonded joint, where intermetallic compounds formed as layers distributed in the order of their chemical compositions. This suggests that the formation of the intermetallic compound layer was significantly influenced by a factor other than the diffusion of Al and Fe. In the steel adjacent to the intermetallic compound layer, a very fine grain zone was observed, suggesting that the steel surface underwent heavy plastic deformation during the friction process. The thickness of the fine grain zone was also increased in proportion to friction time. It was found that the thickness of the intermetallic compound layer increased with that of the fine grain zone, obeying a relation almost independent of the C content of the steel and chemical composition of the Al alloy. These results suggest a significant contribution of mechanical intermingling of Fe with Al in the formation of the intermetallic compound layer. On tensile tests using specimens with a circumferential notch at the interface, the A5052/S45C joint was fractured at the interface region, showing higher fracture strengths than the A5052/S10C joint, probably because of the lesser thickness of the intermetallic compound layer.