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The paper considers the gas nitriding process with cyclic alternation of atmospheres: ammonia and an ammonia mixture with air for strengthening the corrosion-resistant high-alloyed steel 03Cr11Ni10Mo2Ti, designed to operate at cryogenic temperatures. The formation in steel of a nitrided layer of 130—150μm thickness with increased microhardness (more than 12GPa) is shown experimentally. During the final stage in the ammonia and air environment, iron oxides remain in the compound zone, and a sharp drop in hardness is observed at the border of the core. At the completion of the cyclic process with the stage of saturation in ammonia, a nitrides zone is formed based on the γ′-phase, the layer thickness increases (up to 180(…200μm) and the microhardness profile is smoothed, which reduces the risk of embrittlement.

The advantages of nitriding in an electrostatic and high-frequency field connected with the possibility of carrying out processes at normal pressure are shown. The acceleration of the process of diffusion saturation with nitrogen in an electric field with the formation of a spark discharge as compared with gas nitriding is confirmed experimentally. This method of steel nitriding allows forming layers of different structure and thickness with the specified gradient of hardness.

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