Microstructures and Tribological Properties of TiC Reinforced FeCoNiCuAl High-Entropy Alloy at Normal and Elevated Temperature

Abstract

Recent studies have suggested that high-entropy alloys (HEAs) possess high fracture toughness, good wear resistance, and excellent high-temperature mechanical properties. In order to further improve their properties, a batch of TiC-reinforced FeCoNiCuAl HEA composites were fabricated by mechanical alloying and spark plasma sintering. X-ray diffractometry analysis of the TiC-reinforced HEA composites, combined with scanning electron microscopy imaging, indicated that TiC particles were uniformly distributed in the face-centered cubic and body-centered cubic phases. The room temperature hardness of the FeCoNiCuAl HEA was increased from 467 to 768 HV with the addition of TiC, owing to precipitation strengthening and fine grain strengthening effects. As the TiC content increased, the friction coefficient of the FeCoNiCuAl HEA first increased and then decreased at room temperature, due to the transition of the wear mechanism from adhesive to abrasive behavior. At higher temperature, the friction coefficient of the FeCoNiCuAl HEA monotonously reduced, corresponding well with the transition from adhesive wear to oxidative wear.wear resistance of HEAs [8,9]. Recently, it was reported that the addition of Cu can reduce the wear rate of CoCrFeNiCux HEAs at both room temperature and elevated temperatures, and wear resistance at elevated temperatures is promoted more significantly than that at room temperature due to their self-lubricating mechanism [10].However, the major challenge for practical applications of the FeCoNiCuAl HEA is its insufficient strength. Recent studies have indicated that the precipitation of reinforcing phases in various materials, such as HEAs and ceramics, can further increase the yield strength of the alloy while maintaining relatively high ductility [11][12][13]. For instance, the precipitation of SiC nanoparticles in FeCoCrNiMn enhanced the compressive yield strength from 1180 to 1480 MPa at room temperature [14]. The precipitation of WC in the FeCoCrNi HEA leads to an improved hardness up to 768HV, which corresponds well with the transition of the wear mechanism [13]. The alloy may also be strengthened by dispersion strengthening, which can significantly improve the strength and hardness of the alloy, and reduce the plasticity and toughness slightly [15]. TiC is considered a good candidate as the strengthening phase due to its high melting point, high hardness, low density, good metal matrix wettability, good chemical stability, and excellent wear resistance [16]. The optimized yield strength of the (FeCrNiCo)Al 0.75 Cu 0.25 HEA reinforced by TiC particles can reach 1637 MPa, which is increased by 90.6% compared to the (FeCrNiCo)Al 0.75 Cu 0.25 HEA [17]. However, the precipitation of ceramic nanoparticles in the metal matrix tends to be unevenly distributed, which is probably originated from the instability of the interfaces between the ceramic particles and the metal matrix [18][19][20]. In order to make the second phase uniformly distributed in the matrix, in situ methods are widely used to fa...

Tribological Properties of High-Entropy Alloys under Dry Conditions for a Wide Temperature Range—A Review

“…Not all HEAs are solely constructed of only FCC or BCC phases. At times, this is an accident, and may be the result of failed attempts to produce BCC phase materials [ 21 , 29 , 30 , 64 , 67 ]; other times, they may be purposefully developed in hopes of achieving “the best of both worlds” and having some of the high wear properties of BCC phases and the improved ductility of the FCC phases. Per Guo’s valence electron concentration theory, materials with a VEC between 6.87 and 8 tend to have a combination of FCC and BCC phases [ 65 , 68 ].…”

High Entropy Materials: Challenges and Prospects

“…The article on high-entropy ceramics reports on the steps of making (Hf-Ta-Ti-Nb-V)C and (Ta-Ti-Nb-V-W)C high-entropy carbides, and then compositing them with the 19.2 vol% Co binder to make hard metals (also known as cemented carbides) as potential cutting tool materials [9]. Researchers also mix up the TiC and FeCoNiCuAl HEA with mechanical alloying and sinter the mixture into TiC-reinforced FeCoNiCuAl HEA composites with spark plasma sintering, whose hardness and wear performance are largely improved [10]. Lastly, a low-cost bulk metallic glass, Zr 58 Cu 15.46 Ni 12.74 Al 10.34 Nb 2.76 Y 0.5 (at%), is prepared using the industrial grade Zr and its high-cycle fatigue behavior is investigated [11].…”

High Temperature Performance of Spark Plasma Sintered W0.5(TaTiVCr)0.5 Alloy

“…However, the wear resistance decreased for higher WC content due to lower bonding between reinforcement and HEA matrix phases. In contrast, formation of in-situ TiC reinforcement in HEA matrix has been found to be better for the wear resistance [65][66][67]. The formation of in-situ carbide reinforcement enhances the mechanical and tribological properties due to stronger bonding between the ceramic reinforcement and metal matrix [68].…”