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.

The effect of low-temperature liquid borating on the structure and hardness of steel 38KhN3МFА is studied. It is found that in the borating process at temperature 600...660 °C and duration 8...32 hours boride coating with thickness of 6...19 μm with surface hardness of 1900...2000 HV is formed on the steel surface. The optimal borating regimes are determined, in which hardened layer with solid core is formed. The presence of two boride phases FeB and Fe2B in the boride layer is established by metallographic, X-ray and electron microscopic analyzes.

The effect of low-temperature liquid borating on the structure and properties of Ni-resist cast iron is studied. Metallographic studies and optimization of low-temperature liquid borating modes are performed. It is found that after low-temperature liquid borating increases the corrosion resistance of Ni-resist in the reservoir fluid simulator is more than 50 times, and in the washing liquid simulator — more than 100 times compared to the initial state. The developed technology of low-temperature liquid borating provides increase in the water-resistance of Ni-resist cast iron.

Effect of liquid boriding on the structure and properties of 08Kh18N10Т steel is studied by metallographic studies. The dependence of the phase ratio in the boride layer on holding time is established. Corrosion resistance tests in 5 % saline solution and in salt spray chamber are performed. It is shown that the corrosion resistance of 08Kh18N10Т steel practically does not deteriorate after liquid boriding.