Brazed joints in γ TiAl sheet: microstructure and properties

Abstract

γ TiAl sheet offers the potential to replace nickel alloy and steel in some gas turbine applications, with weight savings of up to 40%. Whilst it is recognised that the joining of γ TiAl sheets is a key manufacturing technology for such applications, it is relatively poorly developed and characterised. For this reason, brazing has been studied as a potential route to produce high quality structural joints in γ TiAl sheets. The work reported here has used a Ti–Cu–Ni braze alloy at the joint interface. High strength brazed joints have been produced, with shear properties similar to solid state diffusion bonds in γ TiAl sheet. The range of bonding parameters used produced significant variations in the microstructure of the joints but despite this, the measured shear strengths remained similar. Exposure of the joints to a temperature of 700 °C for up to 1000 h, showed that there was a slight increase in the shear strength with exposure time. However, oxidation studies noted that the brazed joints exhibited significantly poorer oxidation resistance in comparison with the base sheet alloy. This poor oxidation performance was thought to be tolerable and capable of being overcome for aerospace applications.