Microstructure and hardness variation of additively manufactured Ti–Ni–C functionally graded composites

Abstract Ti–Ni–C functionally graded composites were fabricated using a LENS™ additive manufacturing system. A vertical chemical gradient was created by varying powder inputs linearly from Ti–6Al–4V at the bottom layer to approximately 40%wt Ni coated graphite at the top layer. Our results show that the phase constitution, microstructure, and hardness of the composites gradually change with chemical composition. With an increasing Ni coated graphite content, the in-situ synthesised TiC precipitates are distributed more densely, and their morphologies change from tiny flakes to dendrites and finally become coralloid structures. Simultaneously, the hardness of the graded composite increases with the addition of Ni coated graphite.