Numerical Simulation and Experimental Investigation of the Grade R6M5 High-Speed Steel Induction Thermochemical Treatment

Abstract

The results from numerically simulating the induction thermochemical treatment of disk samples made of grade R6M5 high-speed tool steel are presented. The model takes into account the location of the products processed and their heating kinetics inside a sealed chamber in a nitrogen-containing medium. The determination of temperature fields corresponding to nitrogen diffusion processes in steel products (at temperatures above 600 °C) made it possible to determine the product heating depth and uniformity, and the diffusion layer depth. In the course of simulation, the influence of the inductor current in the range of 3.3–3.7 kA on the sample surface temperature during 10 min of treatment was established. The numerical simulation process involved solution of the electrodynamics and unsteady heat transfer boundary problem in the inductor–chamber–sample system. The influence of the inductor current on the steel product average temperature was revealed. It has been found that with these current values, the sample surface temperature varies in the range from 900 to 1170°C. Uniform heating for the entire metal product cross-section depth is observed. The study of the nitrogen content in the substrate after treatment has shown that the nitrogen content was 4.9–12.0 at % in the surface layers (up to 50–70 µm) and up to 2.6–4.0 at % in the diffusion layers (from 80 to 150 µm). A nonuniform nitrogen distribution over the product cross-section was obtained. The microhardness data equal to 1928–1950 HV (at a load of 1.98 H) have confirmed the formation of solid nitrides in the surface layer of samples.