Abstract
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.
Highlights
316L stainless steel (Fe–18Cr–11Ni) is widely used for its low corrosion rate, which is attributed to its inner chromium oxide region and outer mixed iron–nickel oxide region [1,2]
Inconel 718 and 316 stainless steel were joined via electron beam melting additive manufacturing technology, and the results showed that precipitates of niobium carbide, and the Laves phase formed in the fusion zone, generally led to solidification cracking [1]
Nekouie et al [11] reported that the microstructure of dissimilar joints could be controlled by adjusting the specific point energy and beam offset when low carbon steel and austenitic stainless steel were welded via laser welding
Summary
316L stainless steel (Fe–18Cr–11Ni) is widely used for its low corrosion rate, which is attributed to its inner chromium oxide region and outer mixed iron–nickel oxide region [1,2]. Kovar (Fe–29Ni–17Co) alloys possess the advantages of low-temperature constant expansion, and thermal expansion properties and a good thermal matching performance similar to Si, Ge, and glass, obtaining wide application in the electronics industry [3,4,5]. Inconel 718 and 316 stainless steel were joined via electron beam melting additive manufacturing technology, and the results showed that precipitates of niobium carbide, and the Laves phase formed in the fusion zone, generally led to solidification cracking [1]. Nekouie et al [11] reported that the microstructure of dissimilar joints could be controlled by adjusting the specific point energy and beam offset when low carbon steel and austenitic stainless steel were welded via laser welding. In order to further obtain a high strength and high stability dissimilar joints, a filler material that usually possessed good plasticity or an intermediary coefficient of thermal expansion between parent materials was adopted [14,15,16]
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