THERMOCHEMICAL TREATMENT OF MACHINERY COMPONENTS FOR IMPROVED CORROSION RESISTANCE

摘要

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 ?' 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.