Effect of Brazing Clearance on Microstructure and Hardness of Vacuum Brazing Joint of 316L Stainless Steel

Vacuum brazing of 316L stainless steel with BNi-2+40%BNi-5 nickel-based mixed filler metal was carried out to obtain the joints with 3 kinds of brazing clearances.Microstructure of solder joints,element distribution and microhardness of the joints were studied by means of optical microscopy,scanning electron microscopy,energy dispersive X-ray spectroscopy and microhardness testing.The results show that the joints were composed of solid solutions continuous,eutectic compounds and meshwork compounds.The amounts of intermetallic compounds decreased,the joint composition and hardness distribution were more uniform with the decrease of brazing clearance.Continuous microstructure of the joint with 30 μm brazing clearance was mainly solid solution,and the comprehensive properties were the best.