Enhancement of hardness and high-temperature oxidation resistance of Cr/FeCrAl dual-layer plasma-sprayed coating on Zr substrate by post-processing

A Cr/FeCrAl dual-layer coating was deposited on a Zr alloy substrate using atmospheric plasma spraying (APS) to potentially consider the requirement of both loss-of-coolant accidents (LOCA) and normal operating conditions of nuclear cladding cores. The as-sprayed coatings have disadvantages, such as porosity and lamellar structures. Hence, post-processing methods were employed to enhance the compactness of the Cr/FeCrAl coating. This work investigates the effects of two distinct post-processing methods on the microstructure, hardness, and high-temperature resistance of the Cr/FeCrAl dual-layer coatings. The Cr/FeCrAl coating subjected to layer-by-layer post-processing exhibited reduced porosity and increased hardness compared to the coating post-processed after spraying. Oxidation at 1000 °C for 180 min resulted in large-area oxidation cracks in the Cr/FeCrAl coating. Upon oxidation at 1200 °C for 60 min, the Cr/FeCrAl coating that underwent layer-by-layer post-processing demonstrated significant improvements in the oxidation resistance of the Zr alloy. In contrast, the Cr/FeCrAl coating that underwent layer-by-layer post-processing effectively enhanced the oxidation resistance of the zirconium alloy.