In this study, single crystal diamonds were brazed on to stainless-steel plate using a nickel-based braze material, BNi-7. This braze material contains phosphorous and silicon in order to lower its melting point and to improve its fluxing behavior. The braze material also contains chromium for improved corrosion resistance. The brazing was performed in a vacuum furnace at a temperature range of 1000°C - 1050°C. In brazing, both silicon, and more particularly chromium, react with the surface of the diamond crystal, which affects the microstructure of the braze layer and forms desirable thin carbide layers on the diamond surfaces for improved wetting and bonding of the diamond to the braze material. The brazed diamonds were removed from the braze layer by electrolytic polishing. The specimens were then studied with scanning electron microscopy (SEM). Cross-sectional specimens were also prepared from the brazed coating structures, and the microstructures were characterized with SEM and energy dispersive X-ray microanalysis (EDX). Specimens for transmission electron microscope (TEM) studies were also prepared. Carbon from the diamond single crystal particles was detected to have dissolved into the braze layer, which explains why the shapes of the individual diamond particles become rounded under the high-temperature brazing process. It was also found that carbon was removed layer by layer from the diamond surfaces. No evidence of the weakening of the structure inside the diamond could be found from the cross-sectional fracture surfaces in the vicinity of the original diamond surfaces. Two different carbide layers, Cr_3C_2 and Cr_7C_3. were found at the interfaces between the diamond and the braze material.
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