Development of a nickel-based filler metal containing a small amount of silicon

Authors tried to develop a new nickel-based brazing filler metal containing no boron and phosphorous to suppress the formation of brittle phases in a brazed layer. The properties of a joint brazed using the new filler metal were investigated and compared with those of a brazed joint using a conventional nickel-based filler metal of BNi-5. The following results were obtained in this study.A new nickel-based brazing filler metal was successfully developed, which contains a small amount of Si and Mn and shows the melting temperature lower than about 1090°C. The hardness of the new filler metal was about 40% that of BNi-5 filler metal containing about 10% Si.In brazing of SUS304 stainless steel, using BNi-5 filler metal, a hard and brittle finally-solidified region appeared in the brazed layers with joint clearance over 100μm. However, using the new filler metal, the finally-solidified region appeared in the brazed layers with joint clearance over 200μm. The hardness of the finally-solidified region in the brazed layer using the new filler metal was about 54% that using BNi-5 filler metal.The tensile strength of a SUS304 joint brazed using BNi-5 filler metal extremely decreased at joint clearance over 100μm. On the other hand, the tensile strength of a joint brazed using the new filler metal decreased at joint clearance over 200μm. It seems that the brittle finally-solidified region formed in a brazed layer causes the joint to decrease the tensile strength.It was shown that the newly developed filler metal is superior to the conventional BNi-5 filler metal in hardness and in tensile strength of joints with wider joint clearance.