Cold sintering of YSZ–Inconel graded cermet using micron‐scale powders

Abstract The development of functionally graded ceramic–metal (cermet) composites, particularly those comprising 8 mol% yttria‐stabilized zirconia (8‐YSZ) and Inconel 718, is critical for high‐temperature applications such as thermal barrier (TB) and aerospace components. Conventional sintering techniques—such as hot isostatic pressing, spark plasma sintering, and directed energy deposition—require high temperatures and pressures, often resulting in detrimental interfacial reactions, grain coarsening, and thermal mismatch‐induced failures within graded layers. In this study, we introduce a cold‐sintering approach to fabricate multilayer graded YSZ–Inconel cermets at an average temperature of 300°C. Leveraging the Hertzian contact stress and transient water, the process induces in situ fracture of coarse YSZ particles (∼30–50 µm), fragments them into nanoparticles (68 ± 22 nm), and subsequently encapsulates the Inconel particles, thereby promoting densification. Post‐sintering heat treatments (400°C–1400°C) were employed to evaluate microstructural evolution and mechanical performance. Field emission scanning electron microscopy (FESEM) and energy‐dispersive X‐ray spectroscopy (EDS) confirmed the formation of compositionally graded layers with minimal interfacial degradation, while Vickers hardness testing demonstrated improvements in mechanical properties across the graded compositions. These findings establish cold sintering as a promising low‐energy processing route for fabricating functionally graded YSZ–Inconel cermets, offering a scalable and thermally efficient pathway for next‐generation TB and high‐temperature structural applications.