Changes in Mechanical Properties of the Wide-Gap Region Brazed with Various Brazing Temperatures and Times

The microstructural changes and the relations between mechanical properties and additive powder with various brazing temperatures and times were investigated. The IN738 and BNi-3 alloy powders were used as an additive and filler metal powders for the brazing process. The wide-gap brazing process was carried out in a vacuum of 2×10-5 torr. The wide-gap region brazed with 60wt.% IN738 additive powder had a microstructure consisting of IN738 additive, and binary eutectic of Ni3B-Ni, and (Cr, W)B. As the brazing temperature and time were increased, the size of IN738 additive powder increased to 181µm, which decreased the amount of low strength Ni3B-Ni eutectic structure, thereby increasing the fracture strength of the wide-gap brazed region. Cracks in the brazed region were observed to propagate through the Ni3B-Ni structure, which lowered the fracture strength of the wide-gap brazed region.