Abstract
High-entropy alloys (HEAs) have shown a wide range of promising structural and functional properties. By the application of coating technology, an economical exploitation can be achieved. The high wear and corrosion resistance of HEAs make them particularly interesting for the application as protective coatings. Especially for alloys with a high chromium content, a high corrosion resistance has been revealed. For the current investigations, the equimolar HEA CrFeCoNi with a single-phase face centered cubic structure is considered as a base alloy system. To increase the corrosion resistance as well as the hardness and strength, the influence of the alloying elements aluminum and molybdenum is analyzed. For the current investigations, the high kinetic process high-velocity oxygen fuel thermal spraying (HVOF) has been considered to produce coatings with a low porosity and oxide content. Feedstock is produced by inert gas atomization. The influence of the alloy composition on the microstructure, phase formation and resulting property profile is studied in detail. A detailed analysis of the corrosion resistance and underlying mechanisms is conducted. The pitting and passivation behavior are investigated by potentiodynamic polarization measurements in NaCl and H2SO4 electrolyte. A distinct improvement of the corrosion resistance can be achieved for the alloy Al0.3CrFeCoNiMo0.2.
Highlights
The multiprincipal alloying approach of high-entropy alloys (HEAs) has gained intensive research interest in the past almost two decades
The influence of the alloying elements aluminum and molybdenum on the corrosion behavior of High-entropy alloys (HEAs) CrFeCoNi high-velocity oxygen fuel thermal spraying (HVOF) coatings was investigated in detail
Potentiodynamic polarization measurements in NaCl and H2SO4 electrolytes reveal no significant influence on the corrosion behavior by adding aluminum to HVOF-coated CrFeCoNi
Summary
The multiprincipal alloying approach of high-entropy alloys (HEAs) has gained intensive research interest in the past almost two decades. Despite the lack of one principal alloying element, the formation of solid solutions with face centered cubic (fcc) or body centered cubic (bcc) structure could be achieved, whereas complex phases were suppressed. One of the first alloys, where the formation of a single-phase fcc structure was reported, is the quinary alloy CrMnFeCoNi (Ref 1). Subsequent studies proved the formation of a single-phase fcc structure for the quaternary alloy CrFeCoNi (Ref 2). A high ductility was typically observed for HEAs with an fcc structure. Their strength and hardness are reduced in comparison with HEAs with a bcc structure (Ref 3). Whereas the fcc structure is retained for low contents, a further increase causes the stabilization of a bcc structure. Due to the high atomic radius and lattice distortion, an increase in hardness can already be achieved for low
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