Studies of Kinetic Plasticity Effect in High-Speed Steels under Martensite Transformation

In the paper the authors study how the kinetic plasticity effects the temporary and residual stresses formed in instrumental steels when cooling. They also present the results of temporary stresses relaxation. This phenomenon was applied within the temperature range of the martensite transformation to reduce the cold cracking of the surfaced metal. The paper shows that the superplasticity effect emerging at the moment of martensite transformation plays the crucial role in temporary stresses relaxation.</jats:p

Simulation of the Carbon Diffusion Saturation Gear from 15Cr2 Steel in the Cementation Process

The studies on cementation focus exclusively on the carbon’s movement. It is described by diffusion equations, often with constant coefficients and without regard to the liaising with temperature. It does not allow to have regard to the further carbon diffusion into the workpiece with the lower temperature range. The most accurate prediction of carbon concentration profiles depending on the parameters of the carburization regime and the chemical composition of steel is possible with the mathematical models using. However, most models show good results for Fe-C austenite without affecting the effect of alloying substitution elements. Taking into account the influence of alloying elements leads to complex empirical dependencies with difficult selected coefficients. It makes their use difficult. The study describes the simulation using the finite element method for the process of austenite’s diffusion saturation Fe-C-Cr system with carbon during cementation. Here is an example of a steel gear 15Cr2 with the temperature influence. The COMSOL Multiphysics program is used to solve the problem numerically. It is found that the model of carbon diffusion in unalloyed austenite for the single-stage cementation regime is in good contact with the experimental data for the Fe-C-Cr austenite of 15Cr2 steel. For a two-stage process, the calculation of the carbon concentration in the surface layer has a slightly greater deviation from the experimental data than it is at a greater depth.</jats:p