The Study of Vacuum Brazing Three Substrates Using the Cu-6Sn Filler
Date Issued
2016
Date
2016
Author(s)
Lu, Han-Wei
Abstract
In this research, Cu-6Sn filler metal is applied in the vacuum brazing of three substrates, Nickel-based alloy (Inconel 600), Iron-Nickel-based alloy (Incoloy 800) and Ferrous alloy (316L Stainless steel) respectively. The corrosion resistance and the mechanical properties of Cu-6Sn filler metals are much superior to those of the copper foils often utilized in traditional brazing. The reduction of melting temperature due to the addition of tin decreases the brazing temperature, which achieves economizing on heat energy as well. Brazing was performed by controlling parameters such as brazing temperature and holding time. The microstructure of brazed joints and the distribution of precipitates were observed by SEM after vacuum brazing, followed by the EPMA quantitative chemical analysis. Furthermore, selected brazed specimens were conducted in shear test. The relationship between microstructure and shear strength were discussed by means of the images of fractured surface and cross section. The experimental results show as follows. For IN-600/Cu6Sn/IN-600 brazed joint, the interface of brazing area contains Cr3C2 carbide precipitates. Its fractograph is dominated by ductile dimple fracture with sliding marks. The specimen brazed at 1080°C for 10 minutes demonstrates the best shear strength of 353±21 MPa. For IN-800/Cu6Sn/IN-800 brazed joint, there are no precipitates formed in brazing area. Grain boundary penetration of molten filler metals in IN-800 substrate is observed as a result of the insolubility between copper and iron. The specimen brazed at 1080°C for 10 minutes demonstrates the best shear strength of 296±25 MPa. For 316L/Cu6Sn/316L brazed joint, diffusion layers are formed by solid state diffusion at 316L/Cu6Sn interface. The characteristics of dimple are much evident in fractured surface as brazing temperature rises above 1080°C. The specimen brazed at 1100°C for 10 minutes demonstrates the best shear strength of 296±25 MPa.
Subjects
Cu-6Sn filler
Ni-based alloy
Ni/Fe-based alloy
Microstructure
Shear Strength
Type
thesis
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