Brazing of Hastelloy X with High-Entropy Alloy Fillers: Thermodynamic Calculations and Microstructural Analysis

This study experimentally investigates the application of a novel high-entropy alloy (HEA) filler, Co10Cr8Cu20Fe6Mn27Ni29, developed through thermodynamic calculations, in the brazing of Hastelloy X under a hydrogen atmosphere with three distinct brazing durations of 60, 90, and 120 min. The HEA filler was synthesized via mechanical alloying over a period of 60 h. The characterization techniques, including x-ray diffraction (XRD), indicated a lattice strain of 0.01% and a reduction in crystallite size to 66.19 nm. Differential scanning calorimetry (DSC) results revealed a melting temperature of 1116 degrees C for the HEA filler. The shear strength of the samples was evaluated, achieving a maximum value of 283 MPa at 60 min, representing the highest shear strength recorded in this investigation. The results indicated that the sluggish diffusion characteristics of high-entropy alloys may reduce undesirable interactions with the superalloy substrates during brazing at elevated temperatures, thereby inhibiting the formation of detrimental secondary phases through restricted interdiffusion at the joint interface. However, prolonged brazing times led to increased continuity and porosity of brittle chromium-manganese oxide compounds along the grain boundaries, potentially compromising joint performance.