Complex thermal-chemical treatments steps influence at diffusion alloying into liquid metal melt media base to properties of surface layers of carbon steels products

This paper investigated the influence of the complex chemical-thermal treatment technology (CTT) on the properties of the carbon steels surface layers. CTT included carburization, diffusion alloying in the medium of low-melting liquid metal melts (DALMMS) and subsequent heat treatment. Cementation was carried out at a temperature of 950 °C, with an exposure time of 8 hours. DALMMS was carried out in the temperature range from 950 °C to 1050 °C. The duration of exposure varied from 1 hour to 8 hours. DALMMS was carried out in a Pb-Bi medium with the addition of 3-5 % Cr powder. The studies were carried out on samples made of St3, 20X13, 40X, 40X13 steels. It was found that characteristics such as coating thickness and chromium concentration in the surface layer depend on the CTT modes and the steels composition. The maximum thickness of the coatings was observed on steel St3 after CTT at a temperature of 1070 °C, with a duration of 8 hours and was 50 microns. Under the same regime, on steel 20X13 the coating thickness was 37 microns, on steel 40X45 microns, on steel 40X13 30 microns. After carrying out the CTT, the chromium concentration on the surface of samples made of steel St3 is 68,8 %, on steel 40X 64,22 %, on steel 20X13 the chromium content is 62,54 %, on steel 40X13 the chromium content is 64,22 %.