Plasma-Sprayed NiCrCuMoB High Entropy Alloy Coating with low oxide content enabled by Boron Alloyed Powder

Due to the unique properties of high entropy alloys (HEAs), their thermal spray coatings have been intensively investigated. However, due to severe in-flight oxidation induced high oxide inclusions within the coatings, their properties are always much lower than their bulk counterparts. In this study, NiCrCuMoB HEA powders containing boron are designed to deposit the HEA coatings with oxide-free molten droplets by atmospheric plasma spraying. The in-flight in-situ deoxidizing effect through boron is examined through the collected HEA particles passing through the plasma jet. The isolated splats are deposited on the polished stainless-steel substrates for examining their oxidation behavior. The coating microstructure and mechanical properties are investigated. Results show that in-flight oxidation of molten particles can be effectively suppressed and oxide-free HEA particles are achieved. Due to the deoxidizing effect of boron, bulk-like HEA coatings with metallurgical bonding and a low oxide content are achieved.