Microstructure and hot corrosion behavior of hot dip siliconized coating on Ni-base superalloy IN738LC

Nickel-based superalloys are widely used at elevated temperature applications because of their high corrosion and oxidation resistance characteristics as well as high stability. To improve the hot corrosion resistance of Nickel-based superalloys, different coatings are applied. In this study, nickel-base superalloy Inconel 738LC was coated via a novel hot-dip diffusion siliconizing process and the corrosion behavior was investigated by XRD, SEM and EDS analyses. A sever degradation and poor hot corrosion resistance was detected by the uncoated sample, while the siliconized coated sample possessed high corrosion resistance. It was figured out that the high hot corrosion resistance of the coated sample was due to the formation of SiO₂ protective scale in the surface layer which protects the substrate elements in the hot corrosion environment. (paper)