高强Cr-Mn-Ni-N亚稳态奥氏体不锈钢的大气腐蚀规律与机理研究

Type Cr-Mn-Ni-N advanced high strength metastable austenitic stainless steels can be produced through the cold deformation of nitrogen-alloyed nickel-saving Cr-Mn series stainless steels. This kind of stainless steels has attracted much attention for its adaptability to the development of resource-saving stainless steels and lightweight vehicles. As nickel-saving high-strength Cr-Mn-Ni-N metastable austenitic stainless steels are mainly used in atmospheric environments, this project focuses on their atmospheric corrosion behavior. Through setting up the simulation test systems for the typical corrosive atmospheres such as marine atmosphere, industrial atmosphere and marine-industrial atmosphere, the following basic contents will be investigated in this project: the corrosion evolution behavior and pit growth processes of this kind of stainless steels in the simulated solutions of typical atmospheres and in the simulated atmospheric environments under dry-wet alternating conditions; the action mechanism and laws of key factors such as cold deformation, alloying elements, corrosive atmospheric pollutants and temperature on the corrosion kinetics processes and pit growth; analysis of the distribution of pit depth; the corrosion progress model of this kind of stainless steels in the typical simulated atmospheric environments and the basic relationship between the alloying elements, cold deformation, strength and corrosion resistance. The results obtained in this project will enrich the basic corrosion knowledge of the cold-deformed stainless steels in atmospheric environments, and have important engineering application values in the fields of stainless steels, automobile and railway vehicles.

氮合金化的节镍型Cr-Mn系不锈钢经冷变形加工可制得先进的高强Cr-Mn-Ni-N亚稳态奥氏体不锈钢，该类不锈钢适应资源节约型不锈钢和轻量化车辆发展的时代主题，备受关注。由于高强Cr-Mn-Ni-N亚稳奥氏体不锈钢主要在大气环境中使用，本课题拟针对海洋大气、工业大气及海洋工业大气等典型的腐蚀性大气，建立模拟试验体系，重点研究该类不锈钢在典型大气模拟液中和干-湿交替模拟环境中的腐蚀演变行为及蚀坑生长过程，阐明冷变形量、合金元素、腐蚀性大气污染物、温度等关键因素对腐蚀动力学过程及蚀坑生长的作用机制与规律；同时分析蚀坑深度的分布规律，探索该类钢在典型模拟大气环境中的腐蚀发展模型以及合金元素和冷变形量与强度和耐蚀性之间的基本关系。本课题研究结果将丰富冷变形不锈钢在大气环境中的基本腐蚀理论，在不锈钢、汽车与轨道车辆等领域具有重要的工程应用价值。

高强CrMnNiN亚稳态奥氏体不锈钢是节镍型Cr-Mn系不锈钢，腐蚀将是其服役时面临的核心问题。鉴于此，本课题针对大气腐蚀环境，采用典型大气模拟溶液及干湿循环试验装置建立试验体系，以204型CrMnNiN系亚稳态奥氏体不锈钢为基础，制备出不同变形量钢板，揭示了亚稳态奥氏体不锈钢腐蚀的电化学机制，阐明了冷轧变形量、合金元素Cu和Cr、溶液酸化等因素对钝化膜与点蚀的作用机理与规律、以及塑性变形对高强钢腐蚀渗氢的作用机制。研究获得了如下重要结果：1)冷轧变形量对亚稳态奥氏体不锈钢组织及力学性能的影响。随着冷轧压下量的增加α’马氏体含量增加。冷轧后易产生滑移带、层错、机械孪晶组织，Cu合金化减少了钢中马氏体含量和位错缺陷。2) 中等变形条件下含铜204型不锈钢在模拟海洋大气溶液中的电化学腐蚀行为。含Cu冷轧钢因表面可形成更加致密且Cr/Fe比较高的钝化膜，具有较低的钝态电流密度和较高的点蚀电位和极化电阻。3) Cu对高变形不锈钢耐蚀性的影响。当冷轧变形量达到55%时，Cu合金化能够增强不锈钢表面钝化膜的稳定性，减小腐蚀电流密度。4)模拟海洋工业大气溶液中的腐蚀行为。随着冷轧变形量的增大，阳极活性溶解电流密度和钝化密度增大、点蚀电位略有降低、浸泡过程中的活性腐蚀速率显著加快、金属Fe和Cr的优先溶解以及金属表面Cu的富集。5)模拟海洋大气溶液中的点蚀行为。随着冷轧变形量的增加，不锈钢中微观应变和位错密度逐渐增加、马氏体和机械孪晶数量逐渐增多，点蚀电位下降、优先发生点蚀的位置由晶界转变为变形带区域。6) 合金元素对冷轧亚稳态奥氏体不锈钢在模拟海洋大气溶液中的腐蚀行为的影响。合金元素Cr的含量从约14%增大到18%，腐蚀阻力增大，钝化膜的缺陷浓度降低，点蚀电位明显升高。7)汽车用高强钢在三种典型大气模拟环境（融雪污染盐大气、海洋大气和工业大气）中的腐蚀及氢渗透行为。塑性变形增大了钢的电化学活性和位错密度，导致大气腐蚀而产生的氢渗透电流密度减小，但渗入钢中的可扩散氢含量增大。