A. E. Smirnov

Computation of carbon concentration curves in vacuum carburizing of steels

The boundary conditions of the diffusion problem in parametric form are determined on the basis of an experimental study of formation of carbon-saturated layers in vacuum carburizing. The boundary conditions are applied in a model of a process with cyclic modes of carburizing. Adequacy of the developed model is confirmed.

Use of vacuum carbonitriding for raising the seizure resistance of gears from steel VKS-10

Saturation of heat-resistant steel VKS-10 with carbon and nitrogen in a low-pressure atmosphere is studied. The possibility of increasing the fineness of the carbonitride phase and the content of retained austenite in vacuum carbonitriding is shown as compared to vacuum carburizing. Subsequent aging results in segregation of a still finer excess phase. The factors controlling vacuum carbonitriding are determined. Comparative estimation of the seizure resistance of carbonitrided layers of steel VKS-10 and carburized layers obtained on traditional heat-resistant steels is performed.

Choice of Boundary Condition for Solving the Diffusion Problem in Simulation of the Process of Vacuum Carburizing

Comparative analysis of three kinds of boundary condition for solution of the diffusion equation in a mathematical model of vacuum carburizing (low-pressure one) is performed for plotting the carbon concentration curves in carbon and alloy steels. With allowance for the special features of mass transfer in formation of the diffusion layer and for the effect of control factors of the carburizing process, the mass transfer coefficient in the equation of the boundary condition of the third kind is evaluated with the help of parametric equations.

A Study of Quenching Cooling in Gaseous Atmospheres

Prismatic sensors of two standard sizes are used to determine the heat-transfer coefficients of high-pressure nitrogen at different turbine rotor speeds of a SECO/WARWICK 10.0VPT-4020/24N vacuum furnace. The adequacy of the values obtained is estimated.

Optimization of Modes of Vacuum Carburizing of Gears from Heat-Resistant Steel VKS-7 on the Basis of Computational Design

Mathematical simulation is used to develop modes of vacuum carburizing providing the specified level of operating properties in high-load gears from steel VKS-7. The computed values of the operating properties are compared to experimental data obtained by testing check pieces subjected to vacuum carburizing by the modes developed.

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.

Mixed-surface impregnation of gear wheels made of 13Kh3N3M2VFB-Sh age-hardenable integrally alloyed steel aimed at improving surface hardness, wear-resistance, and back-to-back endurance

An analysis has been carried out of mixed-surface impregnation of the 13Kh3N3M2VFB-Sh age-hardenable integrally alloyed steel consisting of successive vacuum carburizing, heat treatment, grinding and nitriding in the glow-discharge was made. Test results of samples hardened by mixed-surface impregnation for back-to-back endurance and wear resistance have been presented. It has been shown that mixed-surface impregnation combines the advantages of vacuum carburizing and nitriding. A surface hardness of more than 1000 HV has been achieved via the mixed-surface impregnation of this stated steel.

Structure and Contact Fatigue Strength of Heat-Resistant Steel VKS-7 Hardened Layers After Ion-Plasma Nitriding

Structure is studied for diffusion layers of heat-resistant steel 16Kh2N3MFBAYu-Sh prepared by ion-plasma nitriding, and their phase composition is established represented by ultra-finely dispersed incoherent chromium nitride particles in a solid solution matrix. Contact fatigue strength of the nitrided layer prepared by an optimized regime is determined by experiment. A feature is established for the effect of nitride layer thickness on contact fatigue strength for heat-resistant steel alloyed with nickel. Nitriding regimes are recommended for treating low modulus gear wheels and other similar components whose performance is governed by contact fatigue strength.

Special Features of the Carbonitriding of Parts of Instrument Bearings Designed for Extreme Service Conditions

A study is made of complexly alloyed steel 8Kh4V9F2-Sh, which is used for fabricating parts of engineering bearings operating under extreme conditions. Vacuum processes are shown to be preferable to gas carburizing for hardening the races of precision bearings. Vacuum carburizing is shown to be an effective technique for forming quality diffusion layers.

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.