Abstracts In this work, were studied the structure and properties of the surface composite layer on heat-resistant steel VKS-5, obtained by combined chemical and thermal treatment, combining liquid electrolysis-free boriding with gas and ion-plasma nitriding. The properties of the surface composite layer are analyzed depending on various parameters of chemical and thermal treatment to determine the optimal mode. The study of the microstructure and properties of borated layers has shown that the most optimal properties can be obtained in the boron mode at a temperature of 1010 °C with an exposure time of 8 hours. The study of the microstructure of composite layers has shown that gas nitriding produces a layer of 80 microns in size, which penetrates deep into the borated layer, and in ion-plasma nitriding, the layer size is so small that it is not possible to determine it using optical microscopy. A study of the properties of composite layers obtained by combined chemical-thermal treatment has shown that combined chemical-thermal treatment, combining boriding and ion-plasma nitriding, allows you to get the best combination of high hardness and reduced microfragility.