Hot Corrosion Behavior of Thermal Spray Coating

Austenitic stainless steel AISI 304 and Boiler steels (such as P11, P22, P12) find their largest application in the manufacturing industry. These are preferred because of their superior mechanical strength, surface stability, creep and fatigue resistance. However, they are highly susceptible to hot corrosion. Therefore, surface engineering imparts hot corrosion resistance properties in high temperature corrosive environments. In the present study, Cr3C2-25NiCr coating was deposited on the substrate 304SS by High Velocity Oxygen Fuel (HVOF) technique in order to investigate the behavior of the Cr3C2-NiCr thermal spray coating. The bare specimens were boilier steel alloys P11, P12 and P22. Hot corrosion test was conducted on bare and coated specimens in 40%K2SO4 -40%Na2SO4 -10%NaCl -10%KCl environment at 900 °C for 10 cycles. Corrosion kinetics was monitored using weight gain measurements. Characterization of corrosion products was carried out by scanning electron microscope with energy-dispersive x-ray spectroscopy (SEM/EDS) technique. The observed corrosion resistance of the Cr3C2-NiCr coating can be attributed to the formation of protective oxide scale Cr2O3. The corrosion mechanism of the coating is discussed.