Effect of Plasma Nitriding Temperature on Corrosion Resistance of Nitriding Layer on X80 Pipeline Steel in 3.5%NaCl Solution

Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-31 Cooperative journals: 《腐蚀科学与防护技术》

孙彦伟 陈吉

Abstract： X80 pipeline steel was nitridated by plasma nitriding and then its electrochemical corrosion behavior in 3.5%NaCl solution was studied by means of polarization curves and impedance spectroscopy. As compared to the bare X80 steel, the nitriding steels exhibit a remarkable increment in hardness, which increases with the rising nitriding temperature; the nitriding steels possess higher corrosion resistance with a lower corrosion current density by about one order of magnitude. The formation of ε phase (Fe3N) with a small amount of γ ' phase (Fe4N) dominates on the surface of the steel nitridated at 450 ℃, resulting in a maximium in corrosion potential about -214 mV and a minimum in corrosion current density about 0.56 μA/cm2, respectively, togeter with the hardness increase to about 810 HV. Only the γ 'phase forms on the surface of the steel nitridated at 570 ℃, which contributes to the hardness increase to 930 HV and a obvious decrease of corrosion resistance. The plasma nitriding temperature determines the phase constitutes of the surface nitriding layer and affects greatly its hardness and corrosion resistance.

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