Corrosion properties of high-speed laser-clad Alloy 625 coatings on low-alloy steels and cast irons

Fusion-bonded and low-diluted overlay welded coatings are frequently very thick (> 1mm), which results in high material consumption (kg/m ² ) and expenses. High-speed laser cladding is a novel process that produces thin fusion-bonded and low-diluted coatings with high coverage rates and low heat input. In this paper, high-speed laser cladding was employed to fabricate relatively thin Ni-based Alloy 625 coatings from various powder feedstocks on low-alloy steels and cast irons for corrosion protection. Obtained coatings were characterized by optical microscopy (OM), scanning electron microscopy (SEM), scanning transmission electron microscopy (STEM), X-ray diffraction (XRD), optical surface profilometry, and Vickers microhardness method. Corrosion performances were explored in long-term salt spray tests in a chloride-containing atmosphere. The results demonstrate that low-diluted and defect-free Ni-based coatings protect the base materials in salt spray tests. Powder feedstocks, which included impurities, produced hot cracks in the clads, which resulted in poor corrosion performance.