Microstructural evolution in laser deposited nickel–titanium–carbon in situ metal matrix composites

Laser deposition of a mixture of elemental nickel, titanium, and carbon (graphite) powders via the laser engineered net shaping (LENS) process results in an in situ titanium carbide reinforced nickel metal matrix composites. The composites have been characterized in detail using X-ray diffraction, scanning electron microscopy (including energy dispersive spectroscopy mapping), Auger electron spectroscopy, and transmission (including high resolution) electron microscopy. Both primary and eutectic titanium carbides, observed in this composite, exhibited the FCC-TiC structure (NaCl-type). Detailed characterization of the nickel/titanium carbide interface was carried out using high resolution TEM with the orientation relationship between the phases being 〈1 0 0〉 TiC//〈1 1 0〉 Ni and (0 0 2) TiC//(1¯ 1 1) Ni. Mechanical and tribological testing determined that the composites exhibited a relatively high hardness of 370 VHN and a steady-state friction coefficient of ∼0.5, both improvements in comparison to LENS deposited pure Ni.

Research highlights▶ Laser deposition of Ni–TiC composites with a relatively low volume fraction of refined homogeneously distributed carbide precipitates resulting from an in situ reaction between elemental titanium and carbon (graphite) within the molten nickel pool. ▶ Detailed characterization of the Ni/TiC interface using high resolution TEM. ▶ Evaluation of the microhardness and tribological properties of this novel in situ composite with comparisons to laser deposited pure Ni.