THE CHROMIUM AND MANGANESE DISTRIBUTION IN THE DIFFUSION LAYER OF STEEL 35CrNi2-3 DURING THERMОDIFFUSION SATURATION

Abstract

Increasing the strength, hardness and wear resistance of the material of machine parts and mechanisms has been an urgent task for many decades. The most promising option of its solution is surface hardening. Among the wide variety of surface hardening methods (heat treatment, deformation methods, etc.), in recent time, much attention has been paid to the chemical-thermal treatment methods, which consist in saturating the metal surface with one or more elements. The article describes the features of thermal diffusion saturation of steel 35CrNi2-3 with chromium and manganese at a temperature of 1000°C. A technique for analyzing the obtained coating is presented, based on the possibilities of X-ray spectral microanalysis of the diffusion layer on transverse microsections of the obtained samples. The elemental composition of the diffusion layer was monitored using a JEOL JSM-6460 LV universal scanning (scanning) electron microscope. The results obtained show that the joint diffusion saturation of the surface of steel 35CrNi2-3 with manganese and chromium leads to the formation of an external diffusion layer on the metal surface, consisting of a solid solution of Cr‒Fe‒Mn substitution with a gradient in composition. The average diffusion coefficients of chromium and manganese in the α-phase of chromium were DCr = 3,5·10‒15 m2/s and DMn = 5,14·10‒14 m2/s, respectively; in the γ-phase of iron ‒ DCr == 1,16·10‒17 m2/s and DMn = 1,43·10‒17 m2/s, respectively. The depth of the diffusion layer of chromium in the metal at joint saturation with manganese was 30 μm, the diffusion layer of manganese was 37 μm. The large depth of penetration of manganese into steel is explained by its lower work function of electrons and the contribution of electromigration of manganese ions to diffusion.