SURFACE TREATING METHOD OF IMPROVING ABRASION RESISTANCE AND CORROSION RESISTANCE OF IRON AND STEEL

摘要

PURPOSE:To considerably improve the abrasion resistance and corrosion resistance of iron and steel by applying ion nitriding treatment within a vacuum reaction furnace on iron and steel surfaces then letting superheated steam sufficiently flow in and out to form hard and porous oxide films on the foregoing nitrided layer surfaces. CONSTITUTION:The inside of a vacuum reaction furnace 1 having been evacuated is put in a reducing gas atmosphere state by a treating gas feed means 13, in which state heating elements 4 are let to evolve heat. Following to this, with an inside wall shield plate 5 as anode and the work (iron or steel) W as cathode, DC voltage 7 is applied between the both electrodes to generate glow discharge. Next, in this state, mixed treating gases of H2, N2, etc. are supplied and ion nitriding treatment is applied through glow discharging. After the completion of this ion nitriding treatment, the inside of the furnace 1 is evacuated in the state that the work W is held set in the furnace 1, thence superheated steam 21 is introduced therein. When the inside of the furance 1 has increased to 1atm. or more, a hinge valve 22b is opened to allow the superheated steal to flow into or out from the furnace 1 inside to apply oxidation treatment to the work W. In this case, the temperature of the work W is kept at a constant temperature from 400-550 deg.C to complete the oxidation treatment.