In designing technical products it is necessary to choose a material that will provide a quality final product with its properties. There is a need of knowing the materials and the elementary methods of material treatment in order to obtain a useful and functional product with preserved invested values. There are differences in choosing of steel, equipment and technique, and as a consequence, there is a difference in the quality of the final product. Although carbonation can be performed in several ways (in solid, liquid and gaseous media) all processes have a common result, that is creating a carbon-rich surface layer that hardens after quenching. As the hardness alone cannot be an indicator of satisfactory quality, of cement layer, it is necessary to pay attention to the microstructural properties which significantly affects on the overall properties of the work piece and thus to the lifetime of the parts. The theoretical part of this paper gives a brief introduction into steels and cementing steels (types, properties and behaviours depending on temperature) are explained in more detail. Thermal diffusion methods for material treatment are described where the focus is on the process of thermal treatment by cementation. The stages of cementing are also explained which include carbonation, tempering and low temperature yielding with test methods. The experimental part of this paper will focus on analysing the whole process. Starting with preparation of work pieces, heat treatment (cementation process), testing of samples and finally with analysis of obtaining results. Analysis of the results will conclude that the starting chemical composition of the material C-15E, 16MnCr5, 15CrNi13 effects on the carbon depth.