By their unique compositions and microstructures, recently developed high-entropy materials (HEMs) exhibit outstanding properties and performance above the threshold of traditional materials. Wear- and erosion-resistant materials are of significant interest for different applications, such as industrial devices, aerospace materials, and military equipment, related to their capability to tolerate heavy loads during sliding, rolling, or impact events. The high-entropy effect and crystal lattice distortion are attributed to higher hardness and yield stress, promoting increased wear and erosion resistance in HEMs. In addition, HEMs have higher defect formation/migration energies that inhibit the formation of defect clusters, making them resistant to structural damage after radiation. Hence, they are sought after in the nuclear and aerospace industries. The concept of high-entropy, applied to protective materials, has enhanced the properties and performance of HEMs. Therefore, they are viable candidates for today’s demanding protective materials for wear, erosion, and irradiation applications.

Entropy stabilized multicomponent alloys offer remarkable mechanical properties and thermal stability rendering these alloys for high-temperature protective films. A novel septenary CrMnFeHfTiTaV complex concentrated alloy (CCA) film was deposited using magnetron sputtering on 304 stainless steel (SS) and silicon substrates. The phase evolution, nano hardness, and tribological behavior of the film were investigated. The as-deposited CCA film displayed a stable amorphous phase up to 600 °C. The indentation hardness of the CCA film was 6.9 GPa compared to 3.3 GPa of the 304 SS substrate. The ball-on-disc wear tests showed that the coefficient of friction (COF) of 304 SS substrate increased from 0.40 at room temperature to 0.46 at 300 °C, whereas for the CCA film, it decreased from 0.82 to 0.44 due to the formation of a lubricating oxide layer. The COF of the 304 SS and the CCA film was similar at 500 °C, however, the wear rate on the CCA film was 7.9 × 10⁻⁵ mm³ N⁻¹ m⁻¹  and on the 304 SS was 158.6 × 10⁻⁵ mm³ N⁻¹ m⁻¹. The septenary CrMnFeHfTiTaV complex concentrated alloy films offered a robust technology to increase the surface properties of 304 SS and provide wear protection from oxide ceramics such as Al2O3 counter face from RT to 500 °C.

High-entropy materials are promising for high-temperature applications. In order to achieve high-temperature wear resistance, a novel high-entropy alloy based composite, (CrMnFeHf)_7.14(TiTaV)_23.81, was designed and consolidated by spark plasma sintering at 1320 ℃ following thermodynamic simulations using the CALPHAD method. The microstructure of the sintered composite revealed a Ti₃₀V₃₆Ta₁₉Cr₅Mn₅Fe₄Hf₁ body-centered cubic (bcc) high-entropy alloy matrix with C14 Laves phase and carbide particles. The Laves phase and carbide particles of higher hardness were formed in situ during the sintering in a bcc matrix. The dry sliding wear behavior of the composite against Si₃N₄ ceramic counter ball (10 N, 30 min) from room temperature to 600 ℃ was investigated. The high-entropy alloy composite showed a superior resistance to wear against Si3N4 ceramic due to the presence of reinforcing C14 laves phase and carbide particles in the high-entropy alloy matrix. Furthermore, the wear rate reduced with increasing temperature. The dominating wear mechanisms of the high-entropy alloy composite were adhesive wear and abrasive wear at room temperature and 200 ℃, oxidation wear and abrasive wear at 400 ℃ and oxidation wear and delamination wear at 600 ℃. The formation of multiple oxides, presence of Laves and carbide phase contributed to the low volume loss of high-entropy alloy composite during wear tests at high temperatures.