INVESTIGATION OF BONDING PHASE DIMENSION ON SHEAR STRENGTH OF SUPERALLOY BRAZED BY ACTVE FILLER MATERIAL

Abstract

In this study, Nickel based superalloy In 738 LC was brazed by using (Ni-Ti) and ( Ni-Ti-Al) alloys which are an active filler alloys under protective atmosphere ( using a high purity 99.999 Argon gas ). Five brazing temperatures (1135, 1025, 985, 825, 725 ºC) were chosen based on the solidus temperatures of (Ni-Ti) and (Ni-Al) filler alloys in order to investigate the effects of these temperatures on the performance of the brazed joints. Brazing processes were carried out over a period of time (15min) to ensure that the filler alloys were melted completely. The performance of brazing process was evaluated in terms of bonding strength by shear test. The results revealed that a maximum value of shear strength ( 29MPa ) was obtained at brazing temperature ( 985ºC ) as compared with other temperatures. It was observed that the highest shear strength was influenced by the formation of ( Ni3Ti ) phase. Micro - hardness testing appears a gradual increasing in hardness towards the centerline of the joint indicating that the composition of bonded layer consists of a hard intermetallic phases of varying composition at different depth. The samples bonded by ( 5% Ni 5%Ti 90%Al ) at 825ºC revealed the higher value ( 841.7 ) HV due to intermetallic and centerline eutectic constituents in the center of brazing seam.