Influence mechanism of pores defect transverse distribution on pitting failure in Ni-Co dual-phase laser cladding layer

The preparation of Ni-Co dual-phase cladding layer on QT600 surface is an effective way to improve the service performance, pore defects are inevitably introduced during this process. Quantifying the mechanism of influence of pore defect transverse distribution on pitting corrosion in Ni-Co dual-phase cladding layer can provide a significant theoretical foundation for enhancing the service life of cladding layer. In this study, a three-dimensional numerical model was established to examine the effect of pore defect transverse distribution on pitting corrosion in Ni-Co dual-phase cladding layer was established by combining experiments and numerical simulations, and the transient evolution of corrosion behavior including ion migration and ion concentration was revealed. Electrochemical analysis of the cladding layer was conducted using a CS310 electrochemical workstation to evaluate its corrosion resistance. The calculation shows that: When pores already exist and are in contact with pitting pit, for pores at different lateral distances from pitting pit. With the increase of pore distance, the potential difference between the interior and exterior of pitting pit gradually increases, leading to an elevated corrosion rate within the pitting pit. The connection between pores and pitting pit become more prominent, and the passivation film is easier to be destroyed. The connection between the pores and pitting corrosion becomes the main corrosion area in the pitting pit. The experimental results show that the Ni-Co dual-phase cladding layer demonstrating superior corrosion resistance compared to the QT600 surface. The effectiveness of the corrosion model is verified by comparison between the experiment and numerical simulations.