Hot Corrosion Performance of HVOF NiCr-Based Coatings in Coal/Biomass Co-fired Power Plants

The aim of this study was to investigate the corrosion behavior of NiCrSi, NiCrTi, and NiCrMo coatings which were deposited by the HVOF process in an alkali chlo ride environment. The corrosion test was conducted at 600 °C for 100 h of expo sure in an alkali salt vapor environment. The coating performance was characterized by field emission scanning electron microscopy equipped with electron-dispersive spectroscopy and X-ray diffraction. The results show that NiCr-based coatings can reduce the corrosion rate. NiCrSi coating has higher corrosion resistance compared to NiCrTi and NiCrMo coatings, which have a corrosion rate value of 0.42 mm/ year. The addition of Si results in the dispersion of SiO2 particles beneath the coat ing surface and the formation of SiO2 layers on the coating surface, which causes a decrease in the growth rate of Cr2O3, resulting in a thin and continuous protective oxide formation. Meanwhile, TiO2 dispersed in the NiCrTi coating could not act as a selective oxidation of the oxide scale. In addition, Mo dispersion plays a role in the formation of volatile MoO3 and MoCl4, resulting in the formation of spinel NiCr2O4