High Entropy Alloy Coatings for Application as Bond Coating for Thermal Barrier Coating Systems

摘要

High-entropy alloys (HEAs) have potential to be used as high temperature materials and in coating material applications due to their combination of strength, ductility, thermal stability, corrosion and wear resistance. HEAs typically refer to alloys that are comprised of five or more elements, at or near equi-atomic compositions. Some of these alloys are solid solution alloys on simple underlying lattices such as face-centered cubic or body-centered cubic. In this paper, HEA coatings based on NiCoCrAlSi were deposited by high velocity oxy fuel (HVOF) and air plasma spray (APS) processes. The coatings were analyzed for phases, microstructure and composition using xray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). The results showed that BCC/B2 phase is the major phase present in the as-produced HVOF coating that was diffusion heat treated at 1080℃. A small amount of an ordered L12 phase with a FCC crystal lattice was also found to be present. APS coatings of the same composition alloy showed a two-phase structure consisting of the L12 and BCC/B2 phases. The HEA coatings produced by HVOF were tested for oxidation resistance at 1050℃ in air. The coating morphology and oxide scales were examined with the aim of developing a high quality bond coat for thermal barrier coating (TBC) systems.