IN625激光熔覆层腐蚀致微裂纹扩展机理研究

Prpogation Mechanism of Microcracks Caused by Corrosion of Laser Cladded In625 Coating on Nodular Cast Iron in 3.5%NaCl Solution

对QT600球墨铸铁表面熔覆IN625涂层,观察熔覆层显微组织与EDS能谱。对基体与熔覆层进行3.5%NaCl溶液中的电化学腐蚀实验,建立IN625激光熔覆层腐蚀致微裂纹扩展瞬态演变数值模型,考虑微小裂纹已经存在的情况下,熔覆层在恶劣环境工作所诱发的腐蚀过程,分析离子浓度、离子迁移、pH值、电极电位和腐蚀速率等各项数值在腐蚀过程中的瞬态演变规律。结果表明,IN625熔覆层相较于QT600基体耐蚀性显著提升。

IN625 coating was laser clad on the surface of QT600 nodular cast iron,and the microstructure and composition of the clad coating were characterized by means of optical microscope and scanning electron microscope with energy dispersive spectroscope.The electrochemical corrosion behavior of the IN625 clad QT600 nodular cast iron was examined in 3.5%NaCl solution.Meanwhile,a numerical model of the transient evolution of micro-crack growth induced by corrosion of IN625 laser cladding layer was established,considering the corrosion process induced by the existence of micro-cracks in the cladding layer working in a harsh environment.The transient evolution of ion concentration,ion migration,pH value,electrode potential and corrosion rate during corrosion were analyzed.The results show that the corrosion resistance of IN625 clad QT600 nodular cast iron is significantly superior to that of the bare QT600 nodular cast iron.