Advanced Processing of Nickel-Titanium-Graphite Based Metal Matrix Composites

A new class of in situ titanium carbide (TiC)/graphite (C) reinforced nickel matrix composites with variation in composition particularly varying C/Ti ratio have been processed using two different processing techniques. Firstly, via mechanical alloying (MA) followed by spark plasma sintering (SPS), i.e. solid-state processing. Secondly, using Laser engineered net shaping (LENSTM) technique, i.e. metal additive manufacturing technique. Mechanical alloying has gained special attention as a powerful non-equilibrium process for fabricating amorphous and nanocrystalline materials, whereas spark plasma sintering is a unique technique for processing dense and near net shape bulk alloys with homogeneous microstructure. Laser engineered net shaping (LENSTM) is a rapid prototyping technique prominently known for its ability to fabricate full dense complex components and functionally graded materials. These composites consist of an in situ formed and homogeneously distributed TiC precipitates reinforcing the nickel matrix. Additionally, by tailoring the C/Ti ratio in these composites the volume fraction of TiC reinforcement can be altered, and an additional graphitic phase can also be engineered into the microstructure. These Ni-TiC-C composites exhibit excellent microhardness as well as tribological properties as compared to pure nickel. Additionally, microstructure, microhardness and tribological behavior of SPS processed Ni-TiC-C composites have been investigated and compared with LENSTM processed counterparts. SPS processed Ni-Ti-C composites exhibit excellent mechanical, as well as tribological properties as compared to LENSTM, processed samples primarily due to uniformly distributed refined TiC and graphite phases within nickel matrix