Corrosion Performance of Cold-Sprayed Nb-Ni-Si Coating in Molten Glass Environment

A novel coating system of Nb-Ni-Si intermetallic compound was designed for components serving in the aggressive environment containing molten glass. Cold spray process was employed to deposit Nb-Ni-Si coating on the nickel-based superalloy substrate (IN 718), and post-spray heat treatment was adopted to promote the formation of intermetallic compounds in the as-deposited coating. The microstructure and corrosion resistance of the coating against molten glass were investigated. Results show that the as-deposited Nb-Ni-Si coating consists of Nb, Ni and Si pure phases as that in the feedstock, which changes into Nb_xNi_y and Nb₃Ni₂Si during post-treatment at 900 °C. After high-temperature oxidation test, the coating effectively suppresses the inward diffusion of oxygen under the protection of the oxidation of NiO and Nb₂O₅. The corrosion behavior of cold-sprayed Nb-Ni-Si coating in molten silicates 1050 °C for 50 h revealed that molten glass has penetrated the coating, but no obvious diffusion of Cr can be found at the interface between the coating and substrate. The appreciable porosity in the coating that formed during post-heat treatment accounts for the fast penetration of aggressive silicates through the coating.