Microstructure analysis of Co₃FeNb₂ intermetallics coating layer on Ni-Fe-base superalloy

High-temperature intermetallic compound (IMC) Co₃FeNb₂ was deposited on K4169 alloy substrate by argon arc cladding technique. The microstructure and element distribution of the cladding layer were analyzed by scanning electron microscope (SEM),X-Ray diffraction and energy dispersive spectrum (EDS). The results show that an 85 μm thick fusion layer was generated between the K4169 alloy substrate and Co₃FeNb₂ IMC by forming metallurgical bonding without defects such as pores or cracks. EDS analysis and X-ray analysis results reveal that most of the fusion zone microstructure were γ',γ and Co₃FeNb₂ phase, and the diffusion of a small amount of Co and Nb strengthened the fusion zone. Meanwhile, mechanically mixed phases including the substrate γ',γ and Co₃FeNb₂,NbNi₉ IMCs formed in the fusion zone,leading to solid bonding.