Numerical simulation and experimental study on pitting damage of IN625 laser cladding layer

The IN625 laser cladding is extensively utilized in the sectors of aviation, navigation, petroleum, and chemical engineering, among others. When the cladding layer is exposed to harsh environments for extended periods, it is prone to fatigue delamination, pitting corrosion, and other detrimental effects, which jeopardize the performance of the workpiece. Quantitatively elucidating the corrosion failure mechanisms of the cladding layer can provide essential insights for enhancing its service life. This study focuses on investigating the evolution mechanism of pitting corrosion pits on the surface of the cladding layer in a corrosive environment. A numerical model for pitting corrosion in the IN625 cladding layer is established to reveal the transient variations in corrosion rate and electrode potential. The results indicate that the concentration changes of Cl − , Na + , and Ni 2+ in the corrosion pits follow the sequence of Cl − > Ni 2+ > Na + . The pH value in the corrosion pits gradually decreases from the top to the bottom, while the corrosion rate at the top of the pits exhibits minimal variation. As the corrosion rate increases, the pits continue to deepen. Based on electrochemical corrosion experiments conducted on the CS310 M electrochemical workstation between the substrate and the cladding layer, it is determined that the corrosion current density of the IN625 cladding layer is reduced by two orders of magnitude compared to the QT600 substrate, resulting in a 395.5-fold decrease in the corrosion rate. The IN625 cladding layer significantly enhances the corrosion resistance of the substrate.