高氮不锈钢固溶处理及抗晶间腐蚀性能研究

发布时间：2018-05-29 04:57

  本文选题：高氮钢 + 晶间腐蚀　； 参考：《东北石油大学》2017年硕士论文

【摘要】：高氮不锈钢是耐蚀钢材中比较突出的材料之一,氮元素价格低廉,可以将大部分昂贵镍元素替换掉,能稳定钢中奥氏体,更能改善不锈钢局部腐蚀。固溶处理使氮元素在不锈钢中均匀分布,阻碍贫铬区出现,起降低晶间腐蚀的作用。本文采用真空感应熔炼方法,制备高氮奥氏体不锈钢。对制备所得材料的成分、组织和结构进行检测,并在3%(wt)的Na Cl溶液中对其常态以及固溶处理后的极化曲线及阻抗谱进行测试。采用电化学动电位再活化法(EPR)以及草酸侵蚀试验对固溶处理后敏化处理的材料的晶间腐蚀性能进行研究,能够较准确的反映固溶处理对高氮钢的耐晶间腐蚀性能的影响。常态下,升高溶液温度使钝化区间缩小,钝化膜层电阻降低,腐蚀越容易。腐蚀介质由酸性逐渐变为碱性,膜层电阻增大,钝化稳定性能变好。随着固溶温度升高及保温时间增长,使最初为骨架状铁素体转变为光滑的圆形。电化学实验表明,保温时间较短时,随温度升高,钝化电流密度缩小,腐蚀减缓,膜层耐蚀性提高,试样钝化稳定性提高;时间过长时,膜层电阻降低,抗腐蚀能力变差,钝化膜均匀性降低导致腐蚀性能变差。经1050℃保温20min可以得到耐蚀性能较好的试样。EPR测试选用H2SO4+Na2S4O6溶液体系适合检测高氮奥氏体不锈钢。测试表明,保温时间较短,固溶温度升高,再活化率R值降低,电量比Qr/Qa降低;保温时间过长,R值增大,电量比Qr/Qa变大。在草酸浸蚀实验中,选取10%草酸溶液作为电解液,在1A的恒电流下对材料侵蚀90s,结论与EPR实验相一致。保温时间较短,随固溶温度升高,晶粒长大,晶界面积减小,耐晶间腐蚀性强;保温时间过长,析出物等出现,晶间腐蚀沿晶界发生,耐晶间腐蚀性能变差;在1050℃下保温20min试样的耐晶间腐蚀性能优良。
[Abstract]:High nitrogen stainless steel is one of the most prominent materials in corrosion resistant steel. The low price of nitrogen element can replace most expensive nickel elements, which can stabilize austenite in steel and improve local corrosion of stainless steel. The solution treatment makes the nitrogen element distribute uniformly in stainless steel, which hinders the appearance of chromium-poor zone, and plays the role of reducing intergranular corrosion. In this paper, high nitrogen austenitic stainless steel was prepared by vacuum induction melting. The composition, microstructure and structure of the prepared materials were determined, and the polarization curves and impedance spectra of the prepared materials were measured in NaCl solution of 3 wts. The electrochemical potentiodynamic reactivation method (EPRR) and oxalic acid erosion test were used to study the intergranular corrosion properties of the materials sensitized by solid solution treatment, which can accurately reflect the effect of solid solution treatment on the intergranular corrosion resistance of high nitrogen steel. Under normal condition, increasing the solution temperature reduces the passivation interval and decreases the resistance of the passivation film, which makes corrosion easier. The corrosion medium changed from acidic to alkaline, the film resistance increased and the passivation stability improved. With the increase of solution temperature and holding time, the initial skeleton ferrite is transformed into a smooth circle. The electrochemical experiments show that when the holding time is short, the passivation current density decreases with the increase of temperature, the corrosion slows down, the corrosion resistance of the film increases, and the passivation stability of the sample increases, and when the holding time is too long, the resistance of the film decreases and the corrosion resistance becomes worse. The decrease of the uniformity of passivation film leads to the deterioration of corrosion performance. The sample with good corrosion resistance can be obtained by holding 20min at 1050 鈩，

本文编号：1949578