Nano oxides reinforced high-entropy alloy coatings synthesized by atmospheric plasma spraying

Abstract

The high-entropy alloy coatings reinforced with nano oxides were synthesized by the atmospheric plasma spraying (APS). The crystal structure, microstructure, surface morphology, hardness and wear resistance properties of the CoCrFeNiAl and CoCrFeNiMo high-entropy alloy coatings are investigated. For CoCrFeNiAl high entropy coating (HEC) not only has high hardness (573 ± 19 Hv 0.1) but also has good wear resistance [The coefficients of friction (COF) is 0.49 ± 0.04]. The transition of the wear mechanism obviously appears between the two HECs. The influences of the structure, composition and hardness on the tribological behavior of high-entropy alloy coatings were discussed in details. IMPACT STATEMENT Nano oxides enhanced high-entropy coatings (HECs) are successfully fabricated by atmospheric plasma spraying, which exhibit the highest hardness and the best wear resistance in HECs and high-entropy alloys.

Frictional Wear and Corrosion Behavior of AlCoCrFeNi High-Entropy Alloy Coatings Synthesized by Atmospheric Plasma Spraying

“…Generally, during the APS process, when the feedstock powders are injected into the plasma jet, different kinetics and thermal energies are obtained by the particles due to the different particle sizes. Correspondingly, the particles experience various states, including fully-molten, semi-molten and non-molten states [ 24 ]. The semi-molten and non-molten particles can be rebounded from the coatings and exhibit some rough bulges, as shown in Figure 2 a–c.…”

“…The process diagram of frictional wear is shown in Figure 5 a,b illustrates the coefficients of frictions (COFs) for the H1, H2, H3 and H4 coatings as the functions of the sliding time. The small value of the COF indicates a high wear resistance because removing the material requires massive energy [ 24 , 32 , 33 ]. With increasing the wear time, the friction coefficients increase sharply at the initial stage, i.e., from 0 to 170 s, and then gradually reach a constant value.…”

“…During the wear process, the metallic oxides flaked off and randomly distributed on the surface of the coating, which effectively prohibited the occurrence of severe adhesion wear. The effect of reducing friction can adequately grease the friction process between the rubbing-pair and the coating surface because of a denudation of multi-component metal oxides and the formation of the particle-like debris on the surface of the coatings [ 24 ]. Moreover, the wear resistance is proportional to the alloy hardness, according to Archard’s law [ 35 ]; hence, H4 coating shows the best wear resistance among the investigated samples.…”

“…As such, investigations of HEA coatings (HEACs) is one of the upcoming research fields where there is a growing interest among the material scientists and engineers. To date, numerous technologies have been applied to fabricate HEACs [ 16 , 17 ], such as magnetron sputtering [ 18 , 19 ], laser cladding [ 20 , 21 ], spraying [ 22 , 23 , 24 ], electrodeposition [ 25 ] and plasma cladding [ 26 ], which have proved that HEACs can exhibit excellent mechanical and physical properties, for instance, high hardness, wear and corrosion resistance and good and appealing electrical and magnetic properties, as well as excellent performance at high temperatures [ 16 , 17 ].…”

Effect of annealing heat treatment on microstructure and mechanical properties of nonequiatomic CoCrFeNiMo medium-entropy alloys prepared by hot isostatic pressing

“…The Cr 3 O 4 may be generated by the existence of a little oxygen during sintering. The existence of Cr 3 O 4 can effectively prevent the occurrence of serious wear when the alloy is applied in industry and can lubricate the friction process between the alloy surface and the friction material [42]. grain distribution of the as-annealed alloys is uniform, and there is no obvious aggregation region of fine μphase grains, indicating that the low-temperature annealing can regulate the size and the uniformity of the grains.…”