Park Jin Sung, Kang Myeong Hun, Kim Sung Jin
Department of Materials Science and Engineering, Sunchon National University, Suncheon 57922, Republic of Korea.
POSCO Technical Research Laboratories, Gwangyang 57807, Republic of Korea.
Materials (Basel). 2024 Dec 3;17(23):5922. doi: 10.3390/ma17235922.
This study examined the surface-grinding-induced microstructural modifications and corrosion attacks in a penetrating form of a high-Mn-low-Cr casting steel slab under humid environments. Various experimental and analytical findings from field-emission scanning electron microscopy, electron backscatter diffraction, transmission electron microscopy, and electrochemical analyses revealed that the abrasive grinding process led to the formation of a surface deformed region, comprising a recrystallized fine grain layer and multiple streamlines. Corrosion initially occurs preferentially along the boundary areas where Cr(Mn)C particles are precipitated. Moreover, the corrosion products (Fe-based oxy/hydroxides) with a high volumetric expansion ratio detach readily from the surface deformed regions, facilitating the easy penetration of corrosive media. In contrast to conventional low-alloyed steels, which exhibit uniform corrosion behavior, corrosion-assisted penetrating attacks on ground high-Mn-low-Cr casting steel slabs occur more severely and frequently during the summer/dry season (i.e., relative humidity levels around 60% to 80%, rather than 100%) when a thin water film can form on the steel surface. Based on the result, effective technical strategies in terms of metallurgical and environmental aspects to mitigate the risk of corrosion-assisted penetrating attack of high-Mn-low-Cr casting steel were discussed.
本研究考察了在潮湿环境下，高锰低铬铸钢平板以穿透形式呈现的表面磨削诱导微观结构变化及腐蚀侵蚀情况。场发射扫描电子显微镜、电子背散射衍射、透射电子显微镜及电化学分析的各项实验和分析结果表明，研磨过程导致形成了一个表面变形区域，该区域由再结晶细晶粒层和多条流线组成。腐蚀最初优先沿着Cr(Mn)C颗粒沉淀的边界区域发生。此外，具有高体积膨胀率的腐蚀产物（铁基氧化物/氢氧化物）很容易从表面变形区域脱落，从而便于腐蚀性介质的轻易渗透。与表现出均匀腐蚀行为的传统低合金钢不同, 对于磨削后的高锰低铬铸钢平板，当钢表面能形成薄水膜时，腐蚀辅助穿透侵蚀在夏季/旱季（即相对湿度约为60%至80%，而非100%）更为严重和频繁地发生。基于该结果，讨论了从冶金和环境方面减轻高锰低铬铸钢腐蚀辅助穿透侵蚀风险的有效技术策略。
