N. M. Ryzhov

Special Features of Vacuum Carburizing of Heat-Resistant Steel in Acetylene

The mechanism of formation of the diffusion layer due to vacuum carburizing of complexly alloyed steel 16Kh3NVFMB-Sh (VKS5) in a medium of acetylene is considered. It is shown that the process of carburizing occurs in a self-regulation mode without the danger of carbon black due to the high rate of arrival of carbon from the gas medium as a result of catalytic dissociation of acetylene molecules, intense process of carbide formation on the saturated surface, and absence of catalytic activity of carbides. The diffusion layer forms under a thin layer of the carbide phase in a kinetic regime, the intensity of which is determined by the rate of dissolution of carbides.

Control of Carbon Saturation of the Diffusion Layer in Vacuum Carburizing of Heat-Resistant Steels

Features in the control of carbon saturation of the diffusion layer in vacuum carburizing of heat-resistant steel 16Kh3NVFMB-Sh (VKS5) in an acetylene medium are considered. It is shown that the requisite characteristics of the diffusion layer can be provided by changing the time regime of the acetylene feed to the working chamber.

A model of diffusion growth of carbide-phase particles in the carburized layer of heat-resistant steels

A mathematical model of carburization of a complexly alloyed heat-resistant steel is suggested for predicting the chemical and phase composition and structure of diffusion layers that allows for formation of particles of the excess carbide phase in the carburization process. A computer-aided solution of the set of nonlinear equations makes it possible to compute the distribution of the carbon concentration, the volume fraction of the carbide phase, and the distribution of its particles over the thickness of the diffusion layer.

Determination of the coefficient of carbon diffusion for calculating nonisothermal regimes of high-temperature ion nitrocarburizing

Conclusions1.Based on the theoretical concepts that allow for the effect of the temperature in thermocycling on the elastic properties of the crystal lattice of the solid solution we obtained an equation for calculating the coefficient of carbon diffusion and used it in a mathematical model of the process of nonisothermal INC.2.The calculation was used to develop thermocycling regimes of INC that provide the formation of diffusion layers of a great thickness at a saturation time reduced to 4 h.

Combined system for controlling ion cyanidation

High-temperature cyanidation possesses a set of known advantages over carburization but the technological process is more difficult to control. In order to ensure the specified saturation of the diffusion layer both the carburizing and the nitriding capacities of the technological atmosphere are to be controlled precisely. The present article concerns a combined system for controlling cyanidation of low-alloyed steels in an ionized thermodynamically nonequilibrium gas medium, which includes an original method for diagnostics of the processes occurring both in the technological atmosphere and on the saturated surface.