Effect of the Joint Saturation Conditions of Steel With Chromium and Nickel on the Diffusion Layer Depth

Abstract

The destruction of parts of machines and mechanisms made of carbon and structural steels, as a rule, begins with surface corrosion, which can be prevented by applying protective coatings, in particular, by chemical-thermal treatment. The results of laboratory studies on the joint thermal diffusion saturation of steel 35Х2Н3 with chromium and nickel at a temperature of 1000°C for 24 hours are presented. A technique for analyzing the resulting coating based on the possibilities of X-ray spectral microanalysis (EDXA) of the diffusion layer on transverse microsections of the obtained samples is presented. The elemental composition of the diffusion layer was monitored using a JEOL JSM-6460 LV universal scanning electron microscope. Additionally, an experiment was carried out, which made it possible to fix the occurrence of an electric current in the system due to the thermal emission of electrons from the metals of the saturating mixture. It is shown that the complex saturation of structural steel with chromium and nickel has a favorable effect on the depth of the diffusion layer. An effective way to increase the depth of diffusion of chromium and nickel is to use an electron gun (nickel mesh). The diffusion depth of nickel increases by 2 times and chromium by 1.3 times. The fact of electron emission and the occurrence of their directed flow (current strength up to 0.15 mA) from the backfill to the saturated part has been experimentally confirmed. It was established that the magnitude of the emerging current depends on the number of emitted electrons and it is higher when the work function of electrons for the metal in the filling is lower.