Nanoindentation study of mechanical and wear properties of spark plasma sintered Ti-6Ni-xTiCN composites

In this study, monolithic pure Ti and Ti-6Ni-xTiCN composites were fabricated by the spark plasma sintering method and the mechanical and anti-wear characteristics of the fabricated samples were investigated using the nanoindentation technique. Microstructural and phase analysis of the sintered samples showed the predominance of the α-Ti phase in the unreinforced pure Ti matrix. In addition to the α-Ti phase, in-situ TiN, Ti2Ni intermetallic, and undissolved TiCN phases were detected in the matrix of the composites. Nanoindentation results revealed that the hardness (H), elastic modulus (Er) and elastic recovery index (We/Wt) of the investigated samples increase with increasing reinforcement contents under varying loads of 50 mN, 100 mN and 150 mN. The nanomechanical and anti-wear properties of the analysed samples indicated dependency on the applied indentation load. The Ti-6Ni-xTiCN composites displayed higher H/Er, H3/Er2 and We/Wt ratios that signified better wear and impact resistance than the unreinforced pure Ti. Microstructural integrity, which ensures consistency between the anti-wear characteristics obtained through the nanoindentation technique and the conventional wear testing, was achieved in composites containing TiCN nanoceramic contents up to 10 wt%. Ti-6Ni-10TiCN composite displayed the optimum combination of the nanomechanical and anti-wear properties across the applied loads.