Periodic multilayer functionally graded structure of Ni-NbMoTa high-entropy alloy composition materials via laser cladding deposition

As the demand for high-performance components in aerospace and other advanced industries continues to increase, the demand for composite structures that combine functionality, structural integrity, and superior performance increases. In this study, laser cladding deposition (LCD) was employed to fabricate a gradient structure based on a Ni-NbMoTa refractory high-entropy alloy (HEA), resulting in the development of a novel functionally graded material (FGM). An interlayer printing strategy was implemented to deposit Ni and NbMoTa alloys via distinct processing routes, enabling the construction of a three-dimensional gradient architecture. The resulting Ni-NbMoTa HEA FGMs exhibited no macroscopic or microscopic cracks within the gradient transition zone. The crystal structure consisted of a dual-phase solid solution comprising body-centered cubic (BCC) and face-centered cubic (FCC) phases. The average grain size and dendrite arm spacing in the transition zone were approximately 20 and 3 μm, respectively. The microhardness of the Ni-NbMoTa FGMs reached 584.5 ± 39.3 HV, showing a clear correlation between hardness and Ni content. Compared with monolithic NbMoTa fabricated using LCD, the Ni-NbMoTa FGMs demonstrated significantly improved room-temperature mechanical properties, with compressive yield strength, ultimate compressive strength, and compressive strain reaching 1096 MPa, 1445.4 MPa, and 18.2 %, respectively. These findings indicate that the addition of Ni effectively enhances the additive manufacturability of the Ni-NbMoTa gradient refractory HEA by promoting grain refinement and improving both strength and ductility.