Microstructure and High-Temperature Corrosion Behavior of Wire-Arc Sprayed Ni-Based Coatings

Abstract

A series of Ni-based cored wires with different boron contents were designed to prepare corrosion-resistant coatings by two-roll wire-arc spraying. These coatings were evaluated for their potential to provide added protection and reduced maintenance for applications in waste-to-energy (WTE) plants. The as-deposited coatings, which primarily are composed of nanocrystalline particles, exhibit uniform and dense layered structures with porosity of about 3%. The investigators selected thermo-gravimetric techniques to evaluate the high-temperature corrosion behavior of the coatings in molten salt environment (Na2SO4-10 wt% NaCl) at 800°C. The coated surfaces exhibited significantly reduced corrosion rates in comparison to those of the SA 213-T2 substrate during all tests. These results were due to the formation in the coatings of composite surface oxide films, including Cr2O3 and NiCr2O4, which serve to prevent the diffusion or penetration of corrosive species. Furthermore, the boron content appears to have a significant influence on the corrosion behavior of the designed coatings: the coating with the best performance had 16 at. % B added. The wire-arc sprayed Ni-based coatings could be an effective and economical treatment to prevent corrosion and extend the lifetime of super-heater tubes in WTE plants.

High temperature corrosion behaviour of wire arc sprayed Fe based coatings

“…14 Another possibility to reduce the oxidation is to add boron containing filler materials to cored wire because the addition of boron can obviously decrease the oxidation of molten particles during spraying. 15 Moreover, the addition of boron influences positively mechanical properties of coatings such as hardness and wear resistance. [16][17][18] The main objective of the present research is to design new Fe-Cr-Al and Fe-Cr-Al-B cored wires and coat the steel substrates by wire arc spraying.…”