Semenova L.M., Bakhracheva Yu.S. The Increase of Mechanical Properties at Nitrocarburizing with High Nitrogen Content

THE INCREASE OF MECHANICAL PROPERTIES AT NITROCARBURIZING WITH HIGH NITROGEN CONTENT

Lidiya Mikhaylovna Semenova

Doctor of Technical Sciences, Professor, Department of Materials Technology,

Volgograd State Technical University

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Prosp. Lenina, 28, 400005 Volgograd, Russian Federation

Yuliya Sagidullovna Bakhracheva

Candidate of Technical Sciences, Associate Professor, Department of Information Security,

Volgograd State University

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Prosp. Universitetsky, 100, 400062 Volgograd, Russian Federation

Abstract. Periodic changes of external influence on the system is accompanied by the complication of diffusion fluxes, which leads to periodic disruption of equilibrium between the steel surface and process atmosphere, resulting in the system where there are gradients of chemical composition, temperature, specific volume and stress state. In the diffusion layer there are internal processes, such as the change in the solubility of carbon, nitrogen and alloying elements, increasing the density of crystal structure defects, the formation of local zones of high concentration of alloying elements that affect the mobility of carbon and nitrogen.

The diversity of physical and chemical mechanisms of implementation of structural conditions leads to the emergence of some new, unexpected effects and change the stability of the system.

This paper studies the structure and properties of nitrocellulose layers with a high content of nitrogen (to 0.90 %). It is shown that with the change in nitrogen and carbon potentials of the atmosphere at a temperature of nitrocarburizing, energy-intensive structures are formed that leads to significant improvements in mechanical properties of the steel surface. The influence of alloying elements on the formation of nitride and carbonitride phases of different dispersion, including nanoscale dimensions in the structure of tempered nitrosomethane layer.

The influence of nitrogen content on microplasticity is nonmonotonic and reaches a maximum in the steel when the content of nitrogen in solid solution 0.6 %, which provides a high microplastic properties and the ability of the nitrogen austenite to deformation hardening.

Key words: nitrocarburizing, diffusion layer, nitrogen potential of the atmosphere, strengthening technologies, mechanical properties of steel.

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