A novel NiCrAlY-Cu based bond coat for rocket nozzle applications through LP-DED process

Abstract

This study explores the development of a novel bond coat for copper-based substrates with the goal of minimizing thermal expansion mismatch and enhancing thermal life in rocket nozzle applications. The effect of copper (Cu) addition on the microstructure, phase evolution, and thermo-mechanical behavior of NiCrAlY clads fabricated via laser powder-directed energy deposition (LP-DED) is systematically investigated to optimize their performance. SEM and elemental mapping reveal a shift from columnar to cellular substructures with Cu additions up to 20 wt%, while higher Cu contents lead to coarse dendritic growth and Cu segregation at grain boundaries, inducing localized strain and crack formation. XRD and DFT analyses indicate that Cu suppresses the ?-NiAl phase and stabilizes the ?-Ni matrix due to its limited solubility in ? and preferential partitioning into ?. High-temperature XRD and EDS analyses show that while pure NiCrAlY forms a continuous alumina scale, Cu-enriched clads develop fragmented and crack-prone thermally grown oxides (TGOs), compromising the oxidation resistance. KAM analysis suggests reduced lattice strain at 10 wt% Cu, followed by increased dislocation density at higher concentrations. Thermal expansion measurements indicate a significant increase in the coefficient of thermal expansion (CTE) at 10 wt% Cu, improving compatibility with Cu-based substrates. However, further Cu additions yield minimal CTE benefits while degrading mechanical strength. Microhardness declines from ?406 Hv (0 % Cu) to ?251 Hv (40 % Cu) due to solid solution softening and ?-phase suppression. A radar plot comparing key metrics identifies 10 wt% Cu as the optimal composition, offering a balanced property set for regeneratively cooled rocket nozzle systems. © 2025 Elsevier B.V.