Effect of dispersed WC and ZrO₂ nanoparticles on the structure, mechanical, and tribological properties of Co–Cr–Fe–Ni medium-entropy powder alloys

This study is aimed at the development and characterization of Co–Cr–Fe–Ni powder alloys strengthened with WC or ZrO₂ nanoparticles. Compact specimens were produced by mechanical alloying of an equiatomic mixture of Co, Cr, Fe, and Ni powders with the addition of 0.5–2.0 vol. % WC or ZrO₂, followed by hot pressing. XRD analysis confirmed the formation of a single-phase FCC structure, whereas SEM and EDS revealed a uniform distribution of the strengthening particles within the matrix. The best mechanical properties were obtained for the following compositions: (CoCrFeNi) + 1 vol. % WC (hardness 73 HRA, ultimate tensile strength σ_tens = 1292 MPa and bending strength σ_bend = 2267 MPa), (CoCrFeNi) + 1 vol. % ZrO₂ (72.5 HRA, σ_tens = 1360 MPa), and (CoCrFeNi) + 2 vol. % ZrO₂ (σ_bend = 2285 MPa). The strength of the investigated alloys was several times higher than that of powder alloys (CoCrFeNi)_100–xTi_x (x = 4÷12 at. %), which were dispersion-strengthened by secondary phases. The maximum ductility (elongation δ = 2.3 % for (CoCrFeNi) + 0.5 vol. % ZrO₂) exceeded that of Ti-containing analogues by an order of magnitude but was significantly lower than that of unreinforced CoCrFeNi alloys (δ = 56÷88 %). Tribological tests revealed the advantages of the alloy containing 1 vol. % WC, which exhibited the lowest wear rate (0.96·10^–4 mm³/(N·m)) and friction coefficient (μ = 0.69) due to the formation of a stable tribolayer. ZrO₂-containing alloys showed higher wear rates ((2.20–2.22)·10^–4 mm³/(N·m)) and a higher friction coefficient (μ = 0.78) as a result of brittle fracture of the ceramic phase. The properties of the (CoCrFeNi) + 1 vol. % WC alloy make it suitable for applications requiring high strength and wear resistance, whereas ZrO₂-containing alloys require further modification to improve their performance.

1. George E.P., Raabe D., Ritchie R.O. High-entropy alloys. Nature Reviews Materials. 2019;4:515–534. https://doi.org/10.1038/s41578-019-0121-4

2. He M., Eizadjou M., Chen H., Liu H., Chang L., Ringer S.P. Microstructure and properties of CoCrFeNi-based multi-principal element alloys containing C and Sc. Journal of Materials Science. 2022;57:9442–9453. https://doi.org/10.1007/s10853-022-07227-3

3. Cantor B., Chang I.T.H., Knight P., Vincent A.J.B. Microstructural development in equiatomic multicomponent alloys. Materials Science and Engineering A. 2004;375–377(1):213–218. https://doi.org/10.1016/j.msea.2003.10.257

4. Salishchev G.A., Tikhonovsky M.A., Shaysultanov D.G., Stepanov N.D., Kuznetsov A.V., Kolodiy I.V., Tortika A.S., Senkov O.N. Effect of Mn and V on structure and mechanical properties of high-entropy alloys based on CoCrFeNi system. Journal of Alloys and Compounds. 2014;591: 11–21. https://doi.org/10.1016/J.JALLCOM.2013.12.210

5. He J.Y., Wang H., Huang H.L., Xu X.D., Chen M.W., Wu Y., Liu X.J., Nieh T.G., An K., Lu Z.P. A precipitation-hardened high-entropy alloy with outstanding tensile properties. Acta Materialia. 2016;102:187–196. https://doi.org/10.1016/j.actamat.2015.08.076

6. Gali A., George E.P. Tensile properties of high- and medium-entropy alloys. Intermetallics. 2013;39:74–78. https://doi.org/10.1016/j.intermet.2013.03.018

7. Liu B., Wang J., Liu Y., Fang Q., Wu Y., Chen S., Liu C.T. Microstructure and mechanical properties of equimolar FeCoCrNi high entropy alloy prepared via powder extrusion. Intermetallics. 2016;75:25–30. https://doi.org/10.1016/j.intermet.2016.05.006

8. George E.P., Curtin W.A., Tasan C.C. High entropy alloys: A focused review of mechanical properties and deformation mechanisms. Acta Materialia. 2020;188:435–474. https://doi.org/10.1016/j.actamat.2019.12.015

9. Gludovatz B., Hohenwarter A., Catoor D., Chang E.H., George E.P., Ritchie R.O. A fracture-resistant high-entropy alloy for cryogenic applications. Science. 2014; 345(6201):1153–1158. https://doi.org/10.1126/science.1254581

10. Miracle D.B., Senkov O.N. A critical review of high entropy alloys and related concepts. Acta Materialia. 2017;122:448–511. https://doi.org/10.1016/j.actamat.2016.08.081

11. Tong C.J., Chen Y.L., Chen S.K., Yeh J.W., Shun T.T., Tsau C.H., Lin S.J., Chang S.Y. Microstructure characterization of AlxCoCrCuFeNi high-entropy alloy system with multiprincipal elements. Metallurgical and Materials Transactions A. 2005;36(4):881–893. https://doi.org/10.1007/s11661-005-0283-0

12. Tang Z., Gao M., Diao H., Yang T., Liu J., Zuo T., Zhang Y., Lu Z., Cheng Y., Dahmen K., Liaw P., Egami T. Aluminum alloying effects on lattice types, microstructures, and mechanical behavior of high-entropy alloys systems. JOM. 2013;65(12):1848–1858. https://doi.org/10.1007/s11837-013-0776-z

13. Rivera-Díaz-del-Castillo P.E.J., Fu H. Strengthening mechanisms in high-entropy alloys: Perspectives for alloy design. Journal of Materials Research. 2018;33(19): 2970–2982. https://doi.org/10.1557/jmr.2018.328

14. Gwalani B., Soni V., Lee M., Mantri S.A., Ren Y., Banerjee R. Optimizing the coupled effects of Hall-Petch and precipitation strengthening in a Al0.3CoCrFeNi high entropy alloy. Materials & Design. 2017;121:254–260. https://doi.org/10.1016/j.matdes.2017.02.072

15. Shun T.T., Chang L.Y., Shiu M.H. Microstructure and mechanical properties of multiprincipal component CoCrFeNiMox alloys. Materials Characterization. 2012; 70:63–67. https://doi.org/10.1016/j.matchar.2012.05.005

16. Liu W.H., He J.Y., Huang H.L., Wang H., Lu Z.P., Liu C.T. Effects of Nb additions on the microstructure and mechanical property of CoCrFeNi high-entropy alloys. Intermetallics. 2015;60:1–8. https://doi.org/10.1016/j.intermet.2015.01.004

17. Olejarz A., Huo W., Kalita D., Zieliński M., Wyszkowska E., Chromiński W., Diduszko R., Chmielewski M., Jóźwik I., Kurpaska Ł. Cr-rich structure evolution and enhanced mechanical properties of CoCrFeNi high entropy alloys by mechanical alloying. Journal of Materials Research and Technology. 2024;30:1490–1504. https://doi.org/10.1016/j.jmrt.2024.03.116

18. Kumar A., Singh A., Suhane A. Mechanically alloyed high entropy alloys: existing challenges and opportunities. Journal of Materials Research and Technology. 2022;17: 2431–2456. https://doi.org/10.1016/j.jmrt.2022.01.141

19. Zhang Y., Zuo T.T., Tang Z., Gao M.C., Dahmen K.A., Liaw P.K., Lu Z. Microstructures and properties of high-entropy alloys. Progress in Materials Science. 2014;61: 1–93. https://doi.org/10.1016/j.pmatsci.2013.10.001

20. Yeh J.W. Alloy design strategies and future trends in high-entropy alloys. JOM. 2013;65(12):1759–1771. https://doi.org/10.1007/s11837-013-0761-6

21. Berezin M.A., Zaitsev A.A., Romanenko B.Y., Loginov P.A. Effect of mechanical alloying modes on the microstructure, phase composition, and mechanical properties of powder high-entropy Co–Cr–Fe–Ni–Ti alloys. Physics of Metals and Metallography. 2024;125:1472–1485. https://doi.org/10.1134/S0031918X24601707

22. Chen R., Zheng S., Zhou R., Wei B., Yang G., Chen P., Cheng J. Development of cemented carbides with CoxFeNiCrCu high-entropy alloyed binder prepared by spark plasma sintering. International Journal of Refractory Metals and Hard Materials. 2022;103(9):105751. https://doi.org/10.1016/j. ijrmhm.2021.105751

23. Peng S., Lu Z., Yu L. Effects of Y2O3/Ti/Zr addition on microstructure and hardness of ODS-CoCrFeNi HEAs produced by mechanical alloying and spark plasma sintering. Journal of Alloys and Compounds. 2021;861:157940. https://doi.org/10.1016/j. jallcom.2020

24. Li M., Guo Y., Wang H., Shan J., Chang Y. Microstructures and mechanical properties of oxide dispersion strengthened CoCrFeNi high-entropy alloy produced by mechanical alloying and spark plasma sintering. Intermetallics. 2020;123:106819. https://doi.org/10.1016/j.intermet.2020.106819

25. Loginov P.A., Zaitsev A.A., Berezin M.A., Sheveyko A.N., Sidorenko D.A., Eganova E.M., Levashov E.A. Interaction of diamond with CoCrFeNiTi HEA during in situ TEM heating: From early-stage catalytic graphitization to metal carbides. Surfaces and Interfaces. 2025;59:105980. https://doi.org/10.1016/j.surfin.2025.105980

26. Loginov P.A., Fedotov A.D., Sheveyko A.N., Zaitsev A.A., Eganova E.M., Levashov E.A. In situ heating TEM study of the interaction between diamond and Cu-rich CoCrCuFeNi high-entropy alloy. Metals. 2025;15(3):257. https://doi.org/10.3390/met15030257