Joining of TiAl-based alloy and a Ni-based superalloy with a NiCoFeCuSiB high entropy filler metal

To explore the potential significance of high entropy alloys for the joining of extremely dissimilar materials, a NiCoFeCuSiB high entropy alloy was newly designed and used as filler metal to braze TiAl-based alloy and a deformed Ni-based superalloy. The microstructures at the joining interfaces were investigated. The as-cast NiCoFeCuSiB high entropy filler alloy was mainly composed of (Co,Fe,Ni) solid solution and (Ni,Co,Fe,Cu,Si) multi-element complex phase. The wettability experiment results indicated that a lower contact angle and better spreading behavior was obtained on the Ni-based superalloy than TiAl-based alloy at 1120 °C/10 min. At the interface of Ni-based superalloy/NiCoFeCuSiB filler, (Ni,Fe,Cr,Co,Cu,Ti,Al) multi-element complex phase was formed and sound metallurgical bonding was achieved. For the interface close to TiAl-based alloy, the diffusion affect zone consisted of γ-TiAl and γ-TiAl(Cu,Ni) phases was visible. The brazed seam was mainly composed of (Ni,Al,Ti,Fe,Co), (Ni,Al,Ti,Co,Fe,Cu), and (Ni,Fe,Cr,Co,Cu,Ti,Al) multi-element complex phases.