Microstructure and mechanical properties of transient liquid phase bonds between NiAl and a nickel-base superalloy

An investigation of microstructural development in transient liquid phase b onds between the B2 type intermetallic compound NiAl and a nickel-base supe ralloy MM-247 is presented in this paper. The bonds discussed in the paper employed pure copper interlayers. Based on edge-on transmission electron mi croscopy investigations, the paper examines both microstructural developmen t at the bond-line and the influence of bonding on the adjacent substrates. The paper considers the epitaxial growth of the B2 type beta (nominally Ni Al) phase into the joint and the formation of non-epitaxial beta-phase laye rs. The paper also examines the formation of second-phases, including the L 1(2) type gamma'-phase (nominally Ni-3(Al, Ti)), MX type carbides, sigma-ph ase intermetallics and elemental chromium and tungsten. Bond-line and adjacent substrate microstructures for the NiAl/Cu/MM-247 bon ds are correlated with joint mechanical properties determined by room-tempe rature shear testing. The paper compares the microstructure and mechanical properties of NiAl/Cu/MM-247 bonds with those of NiAl/Cu/Ni joints. (C) 199 9 Kluwer Academic Publishers.