Computer simulation of boronizing kinetics for a TB2 alloy

The boron diffusion at the surface of a TB2 alloy was simulated via two mathematical models relying on the numerical resolutions of the system of differential algebraic equations (DAE) for the integral method and ordinary differential equations for the mean diffusion coefficient (MDC) method. Both approaches allowed us to compute the boron diffusion coefficients in TiB2 and TiB for a maximum boron content of 31.10 wt.-% in TiB2 at 1223, 1273, 1323 and 1373 K. The boron activation energies in TiB2 and TiB were evaluated and compared with the data published in the literature. Finally, an experimental validation of both models was made through a comparison of the thicknesses of the experimental layers with the predicted values. Consequently, the simulated thicknesses were in line with the experimental values.

Wear Behavior of Borided Cold-Rolled High Manganese Steel

In this study, a novel high-manganese steel (HMS) was borided at 850, 900 and 950 °C for 2, 4, and 6 h by the pack boriding process. Contrary to previous literature, borided HMS uncommonly exhibited saw-tooth morphology like low alloy steels, and manganese enhanced the boron diffusion. Another striking analysis is that the “egg-shell effect” did not occur. The present study demonstrated the silicon-rich zone for the first time in the literature by EDX mapping. Moreover, the formation mechanism of silicon-rich zones was explained and termed as “compact transfer of silicones (CTS)”. XRD analysis showed the existence of FeB, Fe2B, MnB and SiC phases. The boriding time and temperature increased the thickness of the boride layer from 31.41 μm to 117.65 µm. The hardness of the borided layer ranged from 1120 to 1915 HV0.05. The activation energy of borided HMS was found to be a very low result compared to high alloy steel investigated in the literature. The Daimler-Benz Rockwell-C adhesion test showed that adhesions of borided HMS surfaces are sufficient. The dry sliding wear tests showed that boriding treatment increased the wear resistance of untreated HMS by 5 times. The present study revealed that the boriding process extended the service life of HMS components.

Effect of the Boron Powder on Surface AISI W2 Steel: Experiments and Modelling

The effect of boron powder on surface AISI W2 steel and growth kinetic of the boride layer is studied. Boron powder mixture was used in the powder pack boriding; this process was carried out in the temperature range from 1173 to 1273 K with exposure times ranging from 2 to 8 h. The presence of boride was confirmed by optical microscopy, X-ray diffraction, and the distribution of alloy elements in boride layers with energy-dispersive spectrometry using scanning electron microscopy. A mathematical model of the growth kinetics of the single layer was proposed and boron diffusion coefficient was determined by mass balance equation. The morphology of Fe2B layer was smooth and boron activation energy in W2 steel was estimated as 187.696 kJ·mol−1. The kinetic model was validated with two experimental conditions, a contour diagram describing the evolution of Fe2B layer as a function of time and temperature parameters for industrial application.

Boron Diffusion During Carbon Steel Boriding

Protective boride coatings are obtained by chemical-thermal treatment of powder mixtures during induction furnace heating and micro-arc chemical-thermal treatment. Their usage can significantly increase the reliability and durability of steel products. The calculated composition of the saturating charge and the welding flux used to boride steel 20 samples demonstrates that obtained boride diffusion coatings are characterized by high hardness and an extensive diffusion zone. The most optimal composition of the charge that contains iron and boric acid is found to be in the proportion of Fe-25%+H3BO3-75 %. The analysis of the distribution of microhardness over the cross section of coated samples is carried out. The comparative data for the diffusion coefficients and the thickness of the diffusion layers obtained experimentally are presented. The application of the discussed methods makes it possible to intensify the process of diffusion boriding and to ensure the formation of an extensive diffusion zone on the surface of carbon steel products with a high rate of hardening zone formation. The duration of the process is 5 minutes for the induction treatment and 54.05 s for micro-arc chemical-thermal surfacing. It is the main advantage of the experimental techniques mentioned above.