间歇载荷条件下不锈钢表面/亚表面成分、微结构演化对海水环境磨蚀性能影响的研究

The key moving components of marine engineering equipment usually operate under intermittent loading condition due to complicated environment. However, the current research on the tribocorrosion behavior of marine materials is mainly concentrated on the continuous tribocorrosion, and systematic and thorough studies devoted to the intermittent tribocorrosion are lacking. It was reported that a tribologically transformed zone (TTZ) characterized by varying composition and microstructure was formed on the surface/subsurface of wear track under combined mechanical and electrochemical actions. Our previous work suggests that the formation of TTZ, which improves the repasivation ability and corrosion resistance of stainless steel, is expected to have impact on the tribocorrosion performance and related mechanism. This project intends to comparatively investigate the intermittent tribocorrosion performance of 316L and S32750 stainless steel in 3.5% NaCl solution, and analyze the influence of chemical and structural evolution of TTZ on the repassivation kinetics, corrosion susceptibility and mechanical properties under different applied loads and potentials. The dependency relationships of microstructure, normal load and applied potential to the intermittent tribocorrosion performance are expected to be built, and research results will provide theoretical guidelines to prevent or retard the tribocorrosion failure.

受复杂多变的外部环境影响，海工装备关键运动部件多承受间歇式载荷的服役工况；但当前国内外针对海洋工程材料磨蚀行为的研究多集中于连续性载荷的情况，对间歇式载荷下的磨蚀行为及机理尚缺乏系统深入的研究。有报道指出，在力学—电化学联合作用下，材料磨痕区会发生表面/亚表面的成分、微结构改变，形成摩擦变形区。我们前期的研究发现，摩擦变形区的形成促进了不锈钢的再钝化能力，提高了其腐蚀抗力，将对后续的磨蚀性能与机理产生影响。本项目拟开展对316L和S32750两种不锈钢在3.5% NaCl溶液中间歇式磨蚀性能的对比研究，考察磨痕区表面/亚表面成分、微结构在不同载荷、电位下的演化规律，并阐明其对再钝化动力学、腐蚀敏感性和力学性能的影响，由此揭示间歇式载荷下不锈钢磨蚀性能与显微结构、载荷和电位的依赖关系，为海工装备关键摩擦副材料在服役过程中磨蚀失效的预防或减缓提供理论指导。

随着新世纪“蓝色革命”的兴起，海洋开发和利用愈发受到世界各濒海国家和地区的重视，并随之带来了面向海洋应用的高性能材料的研发热潮。面对涉海金属运动部件在力学—电化学耦合作用下易出现磨蚀失效的问题，开展海洋用金属材料及防护涂层在不同工况下的磨蚀行为研究势在必行。由于当前海洋用金属材料及防护涂层的磨蚀研究多侧重于短期、连续载荷下的性能评估，不能满足复杂多变的实海服役工况需求，本项目对316L和S32750不锈钢在3.5 wt.% NaCl中的连续性和间歇式磨蚀行为作对比研究，阐明磨痕区组织结构演化对材料磨蚀性能的影响，揭示间歇式载荷下不锈钢的磨蚀失效机理。在磨蚀过程中，316L不锈钢磨痕区的近表面组织在反复的机械载荷作用下会发生明显的变形、细化和马氏体相变，形成主要由细长的板条马氏体组成的摩擦变形区；摩擦变形区的形成提高了磨痕区的表面硬度和再钝化能力，促进了钝化膜的生成与增厚，提高了磨痕区的腐蚀抗力；磨痕区表面厚的钝化膜促进了材料在后续磨蚀过程中的摩擦磨损，导致316L不锈钢在3.5 wt.% NaCl中的间歇式磨蚀较连续性磨蚀产生更大的材料损失量。通过本项目的研究，考察了不锈钢磨痕区表面/亚表面成份、微结构在不同电位下的演化规律，阐明了其对材料力学性能和再钝化动力学的影响，进而揭示了间歇载荷条件下不锈钢的磨蚀失效机制，为海工装备用关键摩擦副材料在服役过程中模式时效的预防和减缓提供了理论指导。