Brazing of Silicon Carbide Using Ni Based Alloy and Characterization of the Joints

Experimental investigations conducted on SiC/SiC brazed joints with nickel-tungsten as filler material in active vacuum is presented. Brazing experiments are performed at three different temperatures 1400°C, 1450°C and 1500°C in vacuum (10^-2 m.bar) with a heating rate of 3°C per minute, holding at the peak brazing temperatures for 30 minutes and furnace cooled. The microstructures, leak test and joint strength are observed and analyzed. Microstructures of the brazed joints are examined to know the role of temperature, heating rate, soaking time and brazing atmosphere during the reaction. The joint strength results show that the 1400°C brazing temperature provides better leak proof high strength joints. This is due to the optimum thickness of reaction layer obtained through optimum reaction between the ceramic and the brazing alloy during the reaction.