Formation and anti-corrosion characteristics of electron beam alloyed layers

Abstract

Surface alloys which have composition similar to stainless steel are produced on mild steel substrates by traversing the substrates under electron beam irradiation. Chromium and nickel powders are fixed onto the substrates with water glass. An electro-magnetic deflection system oscillates the beam as if its cross section at the substrate surface looks like a rectangle. A mathematical model is constructed which describes diffusion of alloying elements from powders on the surface into an alloyed layer. It is assumed that the alloying elements diffuse instantaneously into an alloyed layer. The calculated results on the concentration distribution show good agree-ment with experimental results. Anti-corrosion characteristics of the alloyed layers are evaluated by anodic polarization curves measured along Japanese Industrial Standard G 0579. The anodic polarization curves of the alloys were similar to the standard curve of a stainless steel, SUS 304, but show somewhat higher peak current density for passivation. The concentration of water glass in powders should be in the range of 0.8 to 2% to attain good and stable anodic polarization curves. The anodic polarization characteristics are better when the density of chromium and nickel is higher.