A novel method of friction-diffusion welding between TiAl alloy and GH3039 high temperature alloy

To improve the properties of friction welded joints between TiAl alloy and GH3039 high temperature alloy, a new method of friction-diffusion welding is proposed. The friction welding of TiAl to GH3039 was achieved under lower friction and forging pressures, and the generated friction welded joints were then diffusion welded. The interfacial microstructures, intermediate phases and fracture morphology of the friction welded and friction diffusion welded joints were investigated by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), electron probe microanalysis (EPMA) and X-ray diffraction (XRD). It was found that the tensile strength of the TiAl/GH3039 joint was improved via the friction-diffusion welding with appropriate diffusion welding parameters. The strength of the friction welded joint increased from 236 MPa to 314 MPa by diffusion welding at 950 degrees C under 40 MPa for 60 min. The typical interfacial microstructure of the friction welded joint was TiAl/Ti3Al + Al3NiTi2/Al3NiTi2/AlNi2Ti/Ni-3(Al,Ti) + (Ni,Cr)(ss)/(Ni,Cr)(ss)/GH3039. The typical interfacial microstructure of the friction-diffusion welded joint was TiAl/Ti3Al + Al3NiTi2/Al3NiTi2/AlNi2Ti/Ni-3(Al,Ti) + rich Cr-(Ni,Cr)ss/rich Ni-and Cr-(Ni,Cr)(ss)/GH3039. A part of Al3NiTi2 brittle phase formed a eutectic zone with Ti3Al after diffusion welding, which narrowed the relative width of the Al3NiTi2 phase layer and resulted in the improvement of the joint performance. At the interface and fracture, cavities were formed when the diffusion pressure was too low, while cracks were generated when the diffusion pressure was too high. It is concluded that the joint strength of the friction-diffusion welding decreased with either low or high diffusion welding pressure compared with that of friction welding.