Study on the mechanism and correlation of double-pit pitting in ductile iron IN625 laser cladding layer

Abstract

With its excellent strength and toughness, ductile iron is widely utilized in marine applications, including ship propellers, rudders, ship cabin pumps, valves, and pipes. Laser cladding is an emerging environmentally-friendly surface-strengthening technology. Numerous corrosion pits on the cladding layer surface accelerate the corrosion failure process. It is of great significance to quantitatively reveal the evolution of microscopic corrosion transients on the cladding layer and to analyze the interaction mechanism between adjacent corrosion pits. In this article, a cladding layer of IN625 was prepared on the surface of QT600 ductile iron. The microscopic morphology and Energy Dispersive Spectroscopy (EDS) were used to observe the cladding layer. The relationship among ion concentration, ion migration, pH, electrode potential and corrosion rate was analyzed by numerical simulation. Electrochemical corrosion experiments were conducted using the CorrTest electrochemical workstation. The results show that the IN625 cladding layer can effectively improve the corrosion resistance of QT600 ductile iron. The polarization curves show that the corrosion current density decreases by two orders of magnitude, and the corrosion rate decreases by 395.5 times after laser cladding. This study can provide new ideas and methods to enhance the service performance enhancement of ductile iron laser cladding layers in marine environments.