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从环境角度研究了敏化1Cr18Ni9Ti不锈钢在高温水中的腐蚀行为.研究指出,在一定浓度Cl~-和(或)O_2存在情况下,在酸性和中性高温高压水中都会出现应力腐蚀破裂.断口电子金相表明,在氯离子为主的环境中,破裂系晶间型;在氧为主的环境中,破裂系以解理为主的混合型.给出了1Cr18Ni9Ti在高温水中腐蚀的表观和真实动力学曲线,表明腐蚀包含溶解和湿氧化两部分,而以湿氧化为主.借Mossbauer内转换电子谱研究了氧化膜结构与腐蚀的关系,指出在一般腐蚀条件下,膜的主要组分为Fe_3O_4,而在应力腐蚀条件下,膜的主要组分为Fe_2O_3,并且系Fe_2O_3和Fe_3O_4多层重叠结构.当水中添加了一定量的硼,在氧化膜中会局部出现FeBO_3相,既不会引起也不会抑制应力腐蚀.硼的这种“惰性”作用和膜结构中Fe_3O_4相的非化学计量比,膜具有阴离子选择性有关.根据腐蚀电化学,认为应力腐蚀系发生在钝化/过钝化区域,增高Cl~-或O_2含量,从不同角度都会使合金的电位接近过钝化区.Cl~-的作用在于改变阳极极化曲线,O_2的作用在于改变阴极极化曲线.在含Cl~-水中,晶界TiC的迅速溶解是应力腐蚀的主要原因,而在含氧水中,晶粒Fe-Cr-Ni中Cr的选择性溶解是应力腐蚀的主要原因.在分析应力腐蚀的特征后,指出应力既是某些严重腐蚀点形

The corrosion behaviour of sensitized 1Cr18Ni9Ti stainless steel in high tem-perature water was nvestigated from the environment angle. Stress corrosion crack-ing would occur in an acidic or neutral high emperature water in the presenceof a definite concentration of Cl~- and/or O_2. SEM electron fractographic nalysisshowed that in Cl~- containing water cracking was intercrystalline, while in O_2bearing water, racking was of a mixed type, mainly as cleavage. The apparentand real corrosion kinetic curves of Cr18Ni9Ti n high temperature water weregiven. It was shown that corrosion consisted of both dissolution and wet xida-tion, chiefly the latter. The correlation between the structure of the oxide films andcorrosion has een studied by means of Mossbauer internal conversion electronspectroscopy. In the case of general orrosion, the film consisted predominantlyof Fe_3O_4, while in the case of stress corrosion, the film onsisted of a multi-layerstructure with Fe_2O_3 as a predominating layer overlapped with layers containingFe_2O_3 and Fe_3O_4. In a boron containing water, FeBO_3 phase might appear in theoxide film ocally, but it neither caused nor inhibited stress corrosion. This "inert"behaviour of boron is related to he non-stoichiometry of Fe_3O_4 in the film tomake it anion-selective in nature. Based on corrosion-electro hemistry, it may beconcluded that stress corrosion takes place between the passive and transpassive regions n the polarization curve. Increasing Cl~- or O_2 content shifts the potentialof the alloy toward the ranspassive region. The action of Cl~- and O_2 are tochange the anodic and cathodic polarization curve espectively. It was suggestedthat in the Cl~- containing water the rapid dissolution of TiC along boundary sthe main cause of stress corrosion, while in the O_2 bearing water, the selectivedissolution of Cr in the lloy is critical. After thoroughly reviewing the charac-teristics of stress corrosion, the authors were nclined to think that stress not onlyis one of the causes for the serious corrosion pits, but also induced ctive pathswhich accomodate, accelerate and help guide the metallic atoms in the pit in dis-solving egularly. Finally, a preliminary model of stress corrosion cracking of1Cr18Ni9Ti in high temperature high ressure water has been proposed.