Joining of TiAl and steels by induction brazing

In order to develop the joining technology of TiAl and structural steels which gives a low cost and high strength joint, rapid induction brazing was investigated. The active silver based filler metal of 63Ag–35.2Cu–1.8Ti mass% (CUSIL-ABA) and the titanium based filler metal of 70Ti–15Cu–15Ni mass% (TICUNI) were selected. As joining materials, the structural steel AISI4340 and cast TiAl with composition of Ti–33.5Al–0.5Cr–1Nb–0.5Si (mass%) were employed. Brazing temperature and holding time were fixed at 15 K above the liquidus temperature of the filler metals for 30 s. The reactions of the molten filler metal of TICUNI with the base metals were stronger than that of CUSIL-ABA. In addition, a carbide layer, not observed in the brazed metal of CUSIL-ABA, was formed at the interface of AISI4340 and the brazed metal. The strength of the joint using TICUNI was inferior to that of CUSIL-ABA due to the formation of the carbide layer at the interface of AISI4340 and the brazed metal. By rapid induction brazing using CUSIL-ABA filler, a joint strength of 320 MPa at room temperature and 310 MPa at 773 K was obtained.