Improving hot corrosion behaviour of Cr3C2-25NiCr coatings by reinforcing nano yttria-stabilized zirconia at 850 °C

High-temperature corrosion poses a significant threat to the longevity and performance of boiler tube materials in harsh industrial environments, necessitating the development of advanced protective coatings. Yttria-stabilized zirconia (YSZ)-enhanced Cr3C2-25NiC coatings were applied to T22 boiler tube steel using the high-velocity oxyfuel method. Conventional Ni-20Cr, 5 wt.% YSZ- Cr3C2-25NiC and 10 wt.% YSZ- Cr3C2-25NiC composite coatings were prepared. High-temperature corrosion tests were conducted on both uncoated and coated samples in a Na(2)SO(4-)60% V2O5 environment at 850 degrees C under fluctuating thermal conditions. These experiments were carried out in a silicon tube furnace at high temperatures, with each sample subjected to 50 exposure cycles. Each cycle consisted of 1 h in the corrosive environment followed by 20 minutes of cooling at room temperature. Corrosion products were analysed using energy-dispersive x-ray analysis and scanning electron microscopy. The addition of YSZ to the Cr3C2-25NiC coatings significantly improved corrosion resistance, with the Ni-20Cr, 5 wt.% YSZ-Ni-20Cr and 10 wt.% Cr3C2-25NiC coatings reducing overall weight gain by 73.08, 84.70 and 89.96 %, respectively, compared to uncoated T22 steel.