Characterization of pack cemented Ni₂Al₃ coating exposed to KCl(s) induced corrosion at 600 °C

Abstract

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Corrosion behaviour of Ni and nickel aluminide coatings exposed in a biomass fired power plant for two years

“…This is discussed in more detail in Section 4.4. [35]. In the first year of plant testing, the nickel aluminide coating was protective on the majority of the circumference (Figure 13a), however after 2 years, there was no remaining protective nickel aluminide coating.…”

“…Laboratory testing at 600 o C for 1 week in 5%O 2 +40%H 2 O+N 2 with KCl deposit of the nickel aluminide coating used in the power plant exposure revealed that there was reactivity between KCl and the Al 2 O 3 oxide formed on the coating[35]. The reaction rate observed in the laboratory exposures was very low, but the reaction would still lead to release of chlorine species that could with time propagate the corrosion attack observed in the plant exposed samples.…”

Effects of Different Fuel Specifications and Operation Conditions on the Performance of Coated and Uncoated Superheater Tubes in Two Different Biomass-Fired Boilers

“…Exposure of Ni2Al3 coatings on pure Ni with a small amount of KCl at 600 o C showed formation of a potassium, aluminium and oxygen rich corrosion product, but the extent of attack was minimal compared to AISI 304 austenitic stainless steel and pure Ni. 20 The investigations by Vokal et al…”

Danish Experiences in Biomass Corrosion and Recent Areas of Research

“…Thus coatings basing their protective behavior on aluminium have been developed utilizing pack cementation to aluminize both steels and nickel based alloys 50 . After the promising results of Nialuminides obtained on a laboratory scale 51,52 , the demonstration of the performance of these coatings under real service conditions in a biomass fired plant was undertaken for two years. After 1 year's exposure, the coatings had failed in a straw firing plant with 540 °C steam temperature 53 and the causes of failure were probably due to heavy thermal cycling resulting in spallation as well as local chemical breakdown of the protective scale.…”