X-ray microanalysis was used in the qualitative and quantitative study of titanium carbides obtained by deposition of thin titanium films on steel substrates using reactive r. f. sputtering of a pure titanium target. The samples are subjected to high vacuum annealing at a temperatures between 200 and 1000°C for 60 min. The morphological analysis by SEM shows that all films exhibited a dense microstructure. The EDS pattern of X-ray microanalysis shows that the non treated samples mainly consist of titanium. The concentration of Ti decreases progressively with the annealing temperature therefore the carbon and iron concentrations increases, this is as result of atomic interdiffusion between the substrate and the thin film. In the highest temperatures of annealing we note the diffusion of the elements of substrate towards outside layers even for those having weak concentrations. The relationship between mechanical properties and the reaction is carried out by Vickers micro-hardness measurements.