Effect of Cr content on the wetting behavior of Cu–Cr/SiC system

Abstract

Generally, a good wettability of brazing alloys on ceramic is one of the key factors for obtaining reliable joints. Knowing the wettability of brazing alloys on substrate is essentially for brazing. In this work, the isothermal wetting behavior of Cu-xCr alloys (x = 1, 2, 3, 4, and 5 wt%) on contact with SiC were systematically studied by the modified sessile drop method at the temperature ranging from 1120°C to 1240°C and the interfacial microstructure were characterized by microscope (SEM), X-ray diffraction (XRD) and TEM. The addition of 1%Cr effectively improved the wettability of Cu–Cr alloys on SiC and led the system to evolve from a non-wetting to wetting state with the formation of interfacial layer (Cr3C2, Cr23C6 and Cr5Si3). As the Cr concentration increased, the coverage of reaction layer increased which correspondingly decreased the final contact angle and the lowest value θ = 5° was obtained at 1200 °C for the Cu–5Cr/SiC system. Lower temperature had no influence on the final contact angles but only slowed down the spreading rate. The spreading of Cu–Cr alloy on SiC consists rapid-decrease stage and sluggish-decrease stage, respectively. The results offer important information for brazing SiC with metals. Eventually, the wetting process of Cu–Cr/SiC system was schematized.