Complex Method of Structural Steel Treatment

The work is devoted to the identification and analysis of the regularities of the modification of the elemental and phase composition, defective substructure and mechanical properties of carbon steel subjected to complex processing, combining the saturation of the surface layer of the samples with aluminum atoms (alitization) and subsequent nitriding. The material used for the study was carbon steels AISI 5135 and AISI 1020, which in the initial state have a ferrite-pearlite structure. The complex modification was carried out in a single vacuum space on a TRIO installation with a chamber size of $600 \times 600 \times 600$ mm, additionally equipped with a switching block to implement the elion (electron and ion) mode. Alitization was carried out at a temperature of 963 K and a time of 4 hours. Subsequent nitriding of the alitized layer was carried out at a temperature of 803 K for 2 hours. The arc evaporator cathode was made of ASTM 1100 aluminum alloy (98.8% Al). As a result of the performed studies, it was found that the thickness of the modified layer reaches $80\ \mu\mathrm{m}$. The hardness of steel is maximum on the modificated surface and exceeds the hardness of the initial material by 4 times (steel AISI 1020) and 2.7 times (steel AISI 5135). It is shown that the complex modification of carbon steel is accompanied by the formation of a multiphase state containing iron nitrides of the composition Fe4N, Fe3N and aluminum - AlN.