Abstract: Disclosed is a process for manufacturing a corrosion resistant iron-alloy, powered metal or sintered carbide component. In a first step, the component is subjected to an initial thermochemical treatment preferably consisting of nitriding, in a closed furnace in order to form onto the surface of the component a nitrogen diffusion zone followed by the superficial layer consisting of .gamma.' and .epsilon. nitride layers. In a second step, an aqueous solution comprising oxygen, carbon, nitrogen and sulfur is introduced into the furnace for a period of time sufficient to allow transformation of the .epsilon. nitride layer into a porous layer of ferrous oxide(s). This process is particularly efficient and permits to produce a superficial porous ferrous oxide layer thicker than 2 .mu.m onto a nitride steel component.

Abstract: The invention is addressed to preventing full reduction of oxides and enabling nitriding temperature through the oxidized layer to be raised which leads in a relatively shorter time, to formation of thicker and harder superficial layers, diffusion saturated with nitrogen.This aim has been achieved by carrying on the tool oxidation process advantageously for the whole time of the gas nitriding process, the said oxidation process accompanying the gas nitriding process being carried on in steam consisting 5 to 0.5 percent by volume of the whole gas atmosphere, the atmosphere of dissociated ammonia being obtained by the dissociation of ammonia at the presence of steam, the process of a simultaneous nitriding and oxidation of tools being carried on for an arbitrary period of time.