Effect of Heat Treatment on Microstructure of Silicon-containing CrFeCoNi High Entropy Alloys Produced by Low-Pressure Plasma Spraying

We produced silicon-containing CrFeCoNi high-entropy alloy (HEA) deposits using the low-pressure plasma spraying method and assessed their structural and characteristic properties. The alloy deposits, once manufactured, underwent a heat treatment process, during which we closely examined the formation of precipitates. These HEAs were fabricated on substrates, regardless of whether they were subjected to water-cooling or not. In the case of both deposits acquired with and without water-cooling of the substrates, diffraction peaks corresponding to the face-centered cubic (FCC) phase were clearly observed when subjected to high temperature heat treatment at 1273 K. Additionally, we identified the presence of silicon-containing compounds on the deposits. As the heat-treatment temperatures increased, we observed the coarsening of the precipitates. Notably, within the crystal granules of the water-cooled as-sprayed deposits, nanoscale precipitates were generated. Among all the samples, deposits heat-treated at 973 K exhibited the highest precipitate area fraction and hardness. This suggests a correlation between the heat treatment temperature and the resulting properties of the HEA deposits, with 973 K being the point at which the highest precipitate area fraction and hardness were achieved.