离子渗氮温度对X80管线钢渗氮层在 3.5%NaCl溶液中耐蚀性能的影响

研究了X80管线钢在3.5%NaCl溶液中的电化学腐蚀行为。结果表明：经离子渗氮的样品,表面硬度显著提高,且随渗氮温度的升高而增加；渗氮层的耐蚀性明显优于基体材料,腐蚀电流密度降低一个数量级；腐蚀电位明显正移。当渗氮温度为450 ℃时,样品渗氮层由ε相和少量的γ '相构成,表面硬度约为810 HV,耐蚀性最好,腐蚀电流最小,约为0.56 μA/cm²,腐蚀电位最高,约为-214 mV。当渗氮温度为570 ℃时,样品渗氮层全部为γ '相,表面硬度约为930 HV,耐蚀性明显降低。离子渗氮温度显著影响X80钢表面渗氮层的相组成,引起表面硬度和耐蚀性不同。

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

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.