The interaction of Si, Ti, and Mo atoms with pyrolytic graphite substrates has been studied for evaporated layers of about 100 nm and implanted ions with mean ranges between 2 and 4 nm. In the temperature range from room temperature to 1800 K the thermal diffusion of carbon into the evaporated layers has been studied by Rutherford backscattering spectroscopy while the temperature dependence of the carbide formation has been studied by x-ray photoelectron spectroscopy. For all three systems stable carbidic phases are predicted by equilibrium phase diagrams. For Ti the formation of TiC is already observed after room temperature implantation, while for Mo annealing to 1200 K is necessary for Mo2C formation. In the case of Si oxygen contamination due to the air transfer after implantation resulted in a mixed SiOxCy phase which only transformed into a SiC phase at temperatures above 900 K, where the oxygen was released. The temperature range of stability of the carbidic layers was found to be correlated to the melting temperature of the metal–carbide eutectic. Above this temperature the metal atoms rapidly dissolve in the graphite lattice.