Boron Diffusion During Carbon Steel Boriding

Abstract

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.