Effects of alloying elements in GH99 superalloy on microstructure evolution of reactive brazing TiAl/GH99 joints

TiAl-based intermetallics and GH99 superalloy were joined by reactive brazing with Ti filler metal. The interfacial microstructure and the effects of main alloying elements Cr, Mo, W and Co originating in the GH99 superalloy on interfacial microstructure evolution of the joint were investigated. The results showed that the alloying elements were mainly concentrated in (Ni, Cr)(ss) (gamma) phase in the zone adjacent to the GH99 superalloy and Ti3Al(alpha(2)) + alpha-Ti + beta-Ti phase in the middle zone of the joint. Compared with Ni/Ti/TiAl joint, the alloying elements in GH99 superalloy delayed the formation of liquid phase in GH99/Ti/TiAl joint. Furthermore, these alloying elements dissolving into GH99/Ti/TiAl joint were beta-Ti phase stabilizing elements, which promoted the formation of beta-Ti + alpha-Ti + alpha(2) phase. In addition, these alloying elements had positive effects on the ductility and high temperature properties of GH99/Ti/TiAl joint. (C) 2012 Elsevier Ltd. All rights reserved.