Phase transformations occurring during the non-vacuum electron-beam surfacing using a mixture of amorphous boron and chromium powder (from 5 to 30 wt%) as well as the effect of the resulting structure on the corrosion resistance of the surface layers of chromium-nickel austenitic steel have been investigated. It has been found that when processing a powder mixture with a minimum chromium content (5 and 10 wt%), layers with a dense arrangement of borides are formed. Further increase in chromium concentration (20 and 30 wt%) leads to the formation of solid solutions in the modified layer. It has been shown that an increase in the concentration of chromium in the surface layer leads to a twofold increase in the corrosion resistance of the 12Х18Н9T (AISI 302) steel surface.