Abstract
High-entropy alloys (HEAs) represent an innovative development approach for new alloy systems. These materials have been found to yield promising properties, such as high strength in combination with sufficient ductility as well as high wear and corrosion resistance. Especially for alloys with a body-centered cubic (bcc) structure, advantageous surface properties have been revealed. However, typical HEA systems contain high contents of expensive or scarce elements. Consequently, applying them as coatings where their use is limited to the surface represents an exciting pathway enabling economical exploitation of their superior properties. Nevertheless, processing conditions strongly influence the resulting microstructure and phase formation, which in turn has a considerable effect on the functional properties of HEAs. In the presented study, microstructural differences between high-velocity oxygen fuel (HVOF) and high-velocity air fuel (HVAF) sprayed coatings of the alloy AlCrFeCoNi are investigated. A metastable bcc structure is formed in both coating processes. Precipitation reactions are suppressed by the rapid solidification during atomization and by the relatively low thermal input during spraying. The coating resistance to corrosive media was investigated in detail, and an improved passivation behavior was observed in the HVAF coatings.
Highlights
The multi-principal group of high-entropy alloys (HEAs) has gained extensive research interest
Inert gas-atomized feedstock of the High-entropy alloys (HEAs) AlCrFeCoNi was successfully processed by high-velocity oxygen fuel (HVOF) and high-velocity air fuel (HVAF) thermal spraying
The content of pores and oxides is reduced in the HVAF coatings
Summary
The multi-principal group of high-entropy alloys (HEAs) has gained extensive research interest Their properties mainly stem from the ability to form simple solid solutions, preferably with body-centered cubic (bcc) or face-centered cubic (fcc) structure. Despite their complex composition, usually comprised of at least four elements with approximately equimolar composition, the formation of complex and brittle phases can be suppressed. A high wear resistance under various loads and conditions was determined (Ref [2, 3]). These properties make HEAs feasible for coating applications, where the required quantities of these materials can be significantly reduced by limiting them to the surface.
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