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.

Keywords

• Brazing; Active filler alloy; Brazing temperatures; Nickel based superalloy; Shear strength

References

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