EFFECT OF SPRAYING REGIME AND VACUUM ANNEALING ON THE MICROSTRUCTURE AND WEAR RESISTANCE OF PLASMA-SPRAYED CoCrFeNiMn HIGH ENTROPY COATINGS

In this study, coatings based on a high-entropy CoCrFeNiMn alloy were deposited on 316L stainless steel substrates using air plasma spraying with two different regimes. After spraying, the coatings were vacuum annealed at 500°C. The aim of the work was to study the effect of hydrogen flow rate and subsequent annealing on the phase composition, microstructure, and mechanical properties of the coatings. X-ray phase analysis showed that a face-centered cubic (FCC) structure dominates in all samples, but after annealing, especially in the regime APS 2, the formation of σ-phase and oxide phases MnO and MnCr₂O₄ is observed. According to SEM/EDS data, a layered microstructure typical for air plasma sprayed coatings and an increased oxygen content in the upper zone of the coatings after annealing were established. The highest microhardness of 390 HV₀.₂ was recorded for the APS 2a coating, which is associated with the formation of hard secondary phases. However, wear tests showed that the best wear resistance was observed in coatings obtained using the APS 1 and APS 1a regimes, due to a more stable phase structure and a lower tendency to oxidation. The results obtained emphasize the importance of comprehensive optimization of spraying parameters and annealing conditions to improve the performance characteristics of HEA based coatings under friction and wear conditions.

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