A novel plasma-sprayed Cr/FeCrAl dual-layer coating on Zr alloy for potential high-temperature applications

To better meet the requirements in loss-of-coolant accidents (LOCA) and conventional operating conditions in nuclear applications, this work prepared Cr, FeCrAl, and Cr/FeCrAl composite coatings on Zr alloys using plasma spraying technology. The microstructures, hardness, and high-temperature oxidation resistance of coatings are examined. The high-temperature oxidation of coatings was conducted at 1200 degrees C in air for 20, 40, and 60 min. All coatings exhibited characteristic lamellar microstructures accompanied by small pores. The inner layers of the coatings, benefiting from the "compacting effect" of subsequently deposited particles, displayed lower porosity and higher hardness. The order of high-temperature oxidation resistance among the coatings was determined as follows: Cr/FeCrAl coating > Cr coating > FeCrAl coating. Notably, the Cr/FeCrAl composite coating demonstrated exceptional durability even after a 60-min exposure, with no ZrO2 formation and negligible Fe and Cr diffusion. However, oxygen could still reach the Zr substrate due to inherent pores and the lamellar structure in the as-sprayed coatings. Therefore, post-treatments are suggested to mitigate or eliminate these pores, thereby improving high-temperature oxidation resistance.