Cracking behaviour, microstructure evolution, and mechanical properties of GH4169/K477 by laser directed energy deposition

Laser directed energy deposition (LDED) offers great potential for fabricating dual nickel-based alloy blisks, due to its capability for in-suit alloying and creating graded powder-ratio zones to join dissimilar materials. However, blisk blades, which demand high-temperature durability, typically utilise γ'-strengthened nickel-based alloys, such as K477, which present challenges due to their poor weldability and high susceptibility to cracking. This study investigates the manufacturability of γ'-strengthened K477 for blisk blades and the mixtures of K477 and GH4169 for graded powder-ratio zones. The research focuses on the influence of laser power and powder ratios on microstructure, precipitated phases, elemental segregation, and crystal texture to elucidate the mechanisms of cracking. The results reveal that both solidification and liquation cracking contribute to crack formation, with liquation cracking being more pronounced at higher laser power. To address these challenges, an optimised laser power combined with a 0°/90° alternating rotation scanning strategy enables the successful deposition of high-density blocks (>99.8%) suitable for mechanical testing. These deposited blocks demonstrate exceptional mechanical properties at both 25°C and 870°C. This work provides a robust technical foundation for the reliable manufacturing of K477 and its transition zones with GH4169 in dual nickel-based alloy blisks using LDED.