Spark plasma sintered step graded Al₂O₃–NbC composites

Functionally graded materials (FGM) present enormous potential to combine materials with distinct mechanical and thermal properties in a component via a compositional gradient throughout the body. In the present work, step graded Al2O3/NbC composites were assessed in order to obtain a FGM with high hardness and good fracture toughness. Step graded uniaxially pressed cylinders were consolidated by Spark plasma sintering (SPS) into fully dense (>99% TD) crack-free graded bodies. The designed gradient was successfully maintained after sintering and, due to the high density of FGMs, it was possible to obtain a high hardness up to 25.1 GPa and a good fracture toughness of ~5 MPa m^1/2.