Method for producing a double diffusion layer on a high-alloy austenitic steel substrate

Abstract

The subject of the application is a method of producing a double diffusion layer on a substrate made of high-alloy austenitic steel of the Fe—Cr—Ni and / or Fe—Cr—Ni—Mo type, characterized in that it comprises the following steps: a) nitriding the substrate in a reactive atmosphere containing nitrogen and hydrogen (N2 / H2), with a nitrogen content of 20% to 70% by volume, at a temperature of ≤450°C, under a pressure of 1 to 3 hPa, for a time of 2 to 12 hours, after which the substrate is cooled together with the furnace, and b) thermal oxidation of the substrate from step a), carried out without a protective atmosphere, in an air atmosphere, at atmospheric pressure, at a temperature of 375°C to 425°C, for a time of 1 to 12 hours.