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

Abstract

316L stainless steel ) 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.

Effects of Heat Input on Microstructure, Corrosion and Mechanical Characteristics of Welded Austenitic and Duplex Stainless Steels: A Review

“…The HAZ photomicrographs of these weldments show that grain coarsening influence is inducted, which is inclined to recede the joint part and may thus influence the functional performance of the weld joint in practice. With high heat input, the grain-coarsening degree within this zone is comparatively higher, but a small heat input helps to inhibit the grain growth by subjecting the zone to abrupt heat gradients [139]. Hardness is relatively small along the large weld zone of heat input, which includes long dendrites with larger interdendritic spacing, but hardness is improved along with the small weld zone of heat input, which contains comparatively few dendrites along with smaller interdendritic spacing.…”

Influence of Welding Speed on the Microstructure and Mechanical Properties of Electron Beam-Welded Joints of TC4 and 4J29 Sheets using Cu/Nb Multi-Interlayers

“…The dark globular phases (E zone) were distributed in the weld metal with a white phase (F zone) around them, as labeled with E and F in Figure 6a. According to Song et al [28], the Cu-Nb binary phase diagram [29], the Fe-Co-Ni ternary phase diagram [30], and the analysis results of chemical compositions (in Table 5), certain phases are if welding speed is increased to 10 mm/s, as shown in Figure 5c. Combining the analysis of the chemical compositions of zones C and D, the amount of solid solution in the weld metal of the titanium alloy side was increased, which was favorable for the improvement of welded joints' strength.…”

“…The dark globular phases (E zone) were distributed in the weld metal with a white phase (F zone) around them, as labeled with E and F in Figure 6a. According to Song et al [28], the Cu-Nb binary phase diagram [29], the Fe-Co-Ni ternary phase diagram [30], and the analysis results of chemical compositions (in Table 5), certain phases are Figure 6 depicts the microstructure of the kovar alloy side of welded joints at welding speeds of 6 mm/s and 10 mm/s, respectively. As it can be seen, the increase of welding speed had a significant influence on the microstructure of the weld metal of kovar alloy side.…”

“…The dark globular phases (E zone) were distributed in the weld metal with a white phase (F zone) around them, as labeled with E and F in Figure 6a. According to Song et al [28], the Cu-Nb binary phase diagram [29], the Fe-Co-Ni ternary phase diagram [30], and the analysis results of chemical compositions (in Table 5), certain phases are recognized as listed in Table 5. The dark globular phase (E zone) and the white phase (F zone) were composed of α-Fe + γ-Fe and (Cu,Nb) solid solution.…”

Advances in Welding Metal Alloys, Dissimilar Metals and Additively Manufactured Parts

“…Song et al have characterized the interfacial microstructures of 316L stainless steel (Fe-18Cr-11Ni) and a Kovar (Fe-29Ni-17Co or 4J29) diffusion, bonded via vacuum hot-pressing in a temperature range of 850-950 • C with an interval at 50 • C for 120 min and at 900 • C for 180 and 240 min, under a pressure of 34.66 MPa [28].…”