High-temperature corrosion behavior of Ni-50Cr coating deposited by high velocity oxygen-fuel technique on low alloy ferritic steel

Ni-50Cr coatings were deposited using the HVOF technique on low alloy ferritic steel (2.25Cr-1Mo) substrates to improve their performance in high temperature steam environments. Different thermal spray parameters were studied in order to optimize the corrosion resistance of the coatings. High temperature thermal tests at 650 °C in different CO2 atmospheres (air with 0, 15 and 25 vol.% CO2) and thermal cycling tests in air at 550 °C and 650 °C were conducted to study the effectiveness of the coating protection system. The uncoated specimens were severely corroded but no oxidation in the coated substrates was detected. A reduction of 10 times in terms of weight change per area unit in the coated steel was obtained after 360 h of testing respect to that of the uncoated steel.