Cyclic hot corrosion behavior and mechanism of GH4738 superalloy in mixed molten salt

The research on the hot corrosion resistance of nickel-based superalloys is critical to determining and enhancing their service life. Therefore, this study investigates the cyclic hot corrosion behavior of GH4738 alloy coated with a mixed salt (75 wt% Na 2 SO 4 +25 wt% NaCl) at 750 °C and 800 °C. X-ray diffractometer (XRD), scanning electron microscope (SEM), energy dispersive spectrometer (EDS), and transmission electron microscope (TEM) are used to analyze the phase compositions and film structures of the corrosion products, as well as to explore the corrosion mechanism. The results show that a thicker oxide layer is formed at higher temperatures, indicating poorer hot corrosion resistance at elevated temperatures. The corrosion products form at both temperatures to show a distinct layered structure, the outer layer is mainly composed of Cr 2 O 3 and a small amount of TiO 2 , while the inner layer consists of Al 2 O 3 , CrS, and TiS. In addition, it is found that the corrosion mechanism of O, S, and Cl elements in the corrosion process is synergistic and accompanied by alkaline melting.