Formation of titanium carbide by high-fluence carbon ion implantation

Titanium carbide has been prepared by high fluence carbon ion implantation in titanium at temperatures between -70 degrees C and 450 degrees C. The carbon ion dose has been varied between 1.2 and 36 x 10(17) C+-ions/cm(2) and the ion energy between 30 and 180 keV. The carbon concentration distribution, the structure, the morphology and the microhardness have been examined with Rutherford backscattering, transmission electron microscopy, X-ray diffraction and nanoindentation, respectively. The concentration distribution of carbon is characterized by a symmetric Gaussian profile for doses up to 12 x 10(17) C+-ions/cm(2) and a more and more asymmetrical profile for higher fluences. The evolution of the concentration distribution is discussed on basis of swelling and sputtering. Precipitates of the titanium carbide phase can be observed after implantation at -70 degrees C with doses greater than or equal to 3 x 10(17) C+-ions/cm(2). The average diameter of the TiC precipitates is a function of ion dose, temperature and duration of annealing. A significant increase of the hardness in the near surface region of implanted samples can be detected. The measured hardness values depend strongly on ion dose, annealing conditions and the hardness of the unimplanted titanium.