FInterfacial microstructure evolution and mechanical properties of the TLP bonded K416B/GH4648 joints with high-entropy state of using a Fe–Co–Ni–Cu–Si filler

To achieve reliable bonding between K416B and GH4648 superalloys, a low-melting-point FeCoNiCuSi high-entropy alloy (HEA) filler was designed based on thermodynamic calculation simulations and empirical parameters. The filler alloy was found to exhibit solidus and liquidus temperatures of 1061 °C and 1117 °C, respectively. The interfacial microstructure, mechanical properties, and bonding mechanism of joints bonded at 1120 °C–1220 °C for 15 min were investigated. Precipitated phases within the matrix primarily consisted of Si(W, Mo)Cr, (Ti, Nb) 6 Ni 16 Si 7 in the DAZ I, rich-(Nb, Ni, Ti, Co) silicides, rich-(Al, Co, Fe) silicides, rich-(Al, Co, Ni) silicides, rich-Cu phases in the ASZ, and Si(W, Fe, Cr)Co, (Ti, Nb) 6 (Ni, Co) 16 Si 7 in the DAZ II. In addition, a large amount of Ni 3 Al-type γ′ phases was observed to precipitate in the bonding seam matrix. As the bonding temperature increases, the volume fraction of the ASZ within the seam consequently decreases. The bonding seam achieves a high-entropy microstructure when the bonding temperature reaches 1180 °C. Under the synergistic effect of temperature increase and high entropy, the precipitated phase in the eutectic zone is suppressed, and a single FCC solid solution bonding seam is obtained. The joint bonded at 1200 °C for 15 min attains a maximum shear strength of 825 MPa. The athermal solidification zone and diffusion-affected zone exhibit significantly higher hardness and modulus than the isothermal solidification zone. Fracture occurs via a mixed brittle-ductile mode. This study provides valuable insights into the application of high-entropy alloys as advanced filler materials for joining and repairing superalloy components.