Effect of post-oxidizing time on corrosion properties of plasma nitrocarburized AISI 1020 steel

Abstract Plasma nitrocarburized AISI 1020 steels are oxidized for 15, 30 and 60 min to evaluate the effect of post-oxidizing time on corrosion behavior. After plasma nitrocarburizing for 3 h at 570 °C, the compound layer composed of e-Fe 2–3 (N,C) and γ′-Fe 4 (N,C) phases and the diffusion layer above the matrix are observed. The oxide top layer, mainly consisting of magnetite (Fe 3 O 4 ) and hematite (Fe 2 O 3 ) phases, is formed after post-oxidation treatment at 500 °C. However, the oxide layer is degraded severely by spallation as a result of the prolonged oxygen plasma bombardment as the post-oxidizing time increases. The difference in corrosion resistance is mainly attributed to the thickness of the oxide top layer, which is governed by the post-oxidizing time.