Influence of Aluminum and Molybdenum on the Microstructure and Corrosion Behavior of Thermally Sprayed High-Entropy Alloy Coatings

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.

Nb and Mo Influencing the High-Temperature Wear Behavior of HVOF-Sprayed High-Entropy Alloy Coatings

“…It was found that the HVOF coating of Al 0.3 CrFeCoNi consists of a single-phase facecentered cubic (FCC) lattice structure (black line, Figure 3a), which was also often found in studies of Al 0.3 CrFeCoNi [14,44,45]. After adding Nb (χ = 0.5), the peak of the FCC phase shifts to a smaller 2θ due to the higher atomic radius of the element Nb (compared to the other elements), which is dissolved in the solid solution and therefore leads to a higher lattice distortion than without Nb [17].…”

“…Therefore, it can be concluded that the HVOF parameters used are suitable for producing coatings whose chemical composition is almost the same as that of the powder feedstock. The parameters used were chosen by previous work [11][12][13][14][15]37].…”

“…Among common coating techniques, thermal sprayed coatings, especially high-velocity oxygen fuel (HVOF) sprayed coatings, are characterized by these coating properties [8,9]. It is also well known from our own previous studies [10][11][12][13][14][15] that HVOF is promising for applying dense and high wear-resistant HEA coatings. To further improve the wear resistance of HVOF-HEA coatings, additional alloying elements can be added to provide high hardness or form hard secondary phases [16][17][18][19][20][21].…”

A Feasibility Study of High-Entropy Alloy Coating Deposition by Detonation Spraying Combined with Laser Melting

“…The successful deposition of HEA coatings by high-velocity oxy-fuel spraying [3,4], atmospheric plasma spraying [5,6] and detonation spraying [7] has been reported. It is important to note that, in all those works, the HEA coatings were thermally sprayed using pre-alloyed powders produced by ball milling or gas atomization.…”

Removal of Molybdenum from Contaminated Groundwater Using Carbide-Derived Carbon

“…Moreover, the gigantic scale of the oil and gas industry in Qatar is also responsible for contaminating groundwater, as it uses Mo as a catalyst for the desulfurization process [6,9]. Mo is also used in many other industries, such as fertilizers, pigments, corrosion inhibitors, and lubricating oils [10][11][12].…”