Ion beam synthesis of non-stoichiometric titanium carbide: Composition structure and nanoindentation studies

Non-stoichiometric titanium carbide layers TiCx (x = 0.26, 0.49 and 0.78) were synthesized by multiple energies ion implantation at the surface of titanium. The carbon concentration profiles obtained from RBS and SIMS measurements are almost flat over the whole implantation depth, in agreement with the simulation calculation. Grazing incidence X-ray diffraction shows the formation of TiC with an NaCl structure in all cases, in spite of the non-stoichiometric composition; nevertheless a small amount of carbon-titanium solid solution is detected on the TiC0.26 sample. The TiC lattice parameter increases with carbon concentration and the carbide layers are formed with small size crystallites. The XPS C1s and Ti2p peaks and the valence band spectrum show that the carbon is fully bonded to the titanium as carbide. Nanoindentation analysis indicates that the carbide layers present an elasto-plastic behaviour with the elastic part increasing with the carbon concentration. The same trend is observed for the hardness and Young's modulus of the TiCx layers.