Evaluation of the structural changes at a surface level of low and medium carbon steel due to the use and effect of TiO₂and MnO nanoparticles.

Several cuts of a low (ASTM A36) and medium (SAE 1045) carbon steel plate were made to prepare different samples of size 10.16x5.08x1.27 cm, which were polished on the upper face; to eliminate the oxidizing material and polluting residues. Each sample was covered with different nanoparticles on the surface. Five different types of nanoparticles with different sizes were used. We have four oxides: TiO₂ (21 nm) and MnO (50 nm). Each sample was placed in a steel hearth box with a lid; each box, in turn, was introduced into a muffle to carry out heat treatment at 950 °C for 24 hours.

After this time and without low the muffle temperature, each of the boxes with every sample was removed the muffle to implement a cooling process by not severe thermal shock at room temperature. A surface layer of iron oxide, and nanoparticles, was formed on each plate; these layers were ground in a ceramic mortar to obtain powders, which were characterized using the X-ray diffraction technique to find the phases present in these layers. Semiquantitative phase analysis was obtained using HighScore Plus software. As a result, the reaction between nanoparticles and the steel surface at 950°C gave us different percentages of iron oxides such as FeO, Fe₂O₃, and Fe₃O₄. We obtained non-stoichiometric Fe compounds and others with different crystallography and composition according to the different nanoparticles used in the process. We observed the penetration depth level of the nanoparticles in each sample according to the width of the surface layer removed each steel plate.