Synergistic effects of Cr on printability, microstructural stability, and mechanical properties of additively manufactured nickel-based superalloys

The development of high-performance nickel-based superalloys for turbine blades via additive manufacturing (AM) faces a critical challenge in balancing printability and high-temperature mechanical properties. This study utilized pre-alloyed powder mixtures to fabricate alloy samples with varying Cr contents via laser-direct energy deposition (L-DED) based on the ZGH451 alloy. The influence of Cr on the alloy's formability, microstructure, and mechanical properties was systematically investigated. Results indicate that the optimal Cr content (5 wt%–10 wt%) significantly enhances crack resistance, reduces porosity, and refines dendrite spacing. Increasing Cr content improves γ′ phase cubicity and reduces coarsening rates during 1000 °C aging (100 h–1000 h). The optimized 7.5Cr alloy (designated as ZGH451G) exhibit exceptional microstructural stability without TCP phase precipitation, and achieves the ultimate tensile strength of 1279 MPa (20 % elongation) at room temperature and 776 MPa (25.5 % elongation) at 900 °C, outperforming most reported AM superalloys. Deformation mechanisms transition from dislocation cutting (room temperature) to Orowan bypassing (900 °C), correlating with cleavage and micro-void coalescence fracture modes, respectively. This work provides a composition design strategy for crack-free, high-performance AM superalloys with balanced printability and service performance.