THE EFFECT OF THE CARBON CONTENT IN STEEL ON PARAMETERS OF BORON DIFFUSION AND THICKNESS OF DIFFUSION COATING DURING BORATION

This paper presents systematized data on the effect of carbon content in steel on the diffusion parameters and thickness of the boride layer for most carbon steels used in industry, starting with carbon steel 15 and ending with hypereutectic tool steels up to and including U10. Saturation of the steel surface with boron was carried out at temperatures of 850, 950 and 1050 °C using a previously developed and patented saturating medium. An increase in the carbon content in steel leads to an increase in the activation energy of boron diffusion, which in turn leads to a decrease in the thickness of the diffusion layer. At the same time, the decrease in the activation energy is not monotonous and depends on both the carbon content in steel and the temperature of the saturation process. An increase in the temperature of the saturation process leads to a decrease in the activation energy of boron diffusion - on average by 5 kJ/mol for every 100 °C. An increase in the carbon content leads to a decrease in the thickness of the boride layer, and this is most noticeable in the industrially used temperature ranges of boriding - from 950 to 1050 °C. The most significant decrease in the thickness of the boride layer occurs with an increase in the carbon content in the range from 0.35 to 0.50 wt. %. In the ranges of carbon content in steel from 0.15 to 0.35 and from 0.5 to 0.95 wt. %, the nature of the decrease in the thickness of the boride layer can be considered linear.

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