Formation of MoSi₂–HfB₂ – based coatings on a C/C–SiC composite by in situ reactive synthesis

The possibility of forming coatings on a of C/C–SiC composite substrate by slurry painting followed by in situ reactive firing of MoSi₂–HfB₂–Si, MoSi₂–HfSi₂–HfB₂–SiB₄ and MoSi₂–HfSi₂–SiB₄ powder compositions at 1620 °C and an argon pressure of ~100 Pa was investigated. The resulting coatings exhibit a framework structure formed mainly by fragmentarily sintered MoSi₂ grains with uniformly distributed HfB₂ particles between them. The synthesized HfB₂ particles have a polyhedral morphology with sizes of 5 to 10 μm and also form nanowhiskers 100–200 nm thick and 2–4 μm long. A sequence of reactions occurring in the MoSi₂–HfSi₂–HfB₂–SiB₄ and MoSi₂–HfSi₂–SiB₄ systems is proposed, which determines the in situ synthesis of secondary HfB₂ and SiC phases. It was established that grain sintering occurs only fragmentarily and proceeds predominantly by a liquid-phase mechanism, as indicated by the presence of numerous highly compact fragments in the structure (especially in the MoSi₂–HfSi₂–SiB₄ system). However, the fraction of the transient liquid phase in both systems is insufficient to obtain coatings with the required high structural continuity throughout the volume. Physicochemical calculations were carried out for the investigated systems. It is shown that, depending on the composition, the total porosity of the coatings is approximately 53–57 %. Silicon evaporation and pyrolysis of the organic binder during heat treatment make the greatest contribution to the formation of discontinuities, producing porosity of 29–37 and 20–25 %, respectively. Promising approaches to reducing the porosity of coatings formed by this technology are identified.

1. Astapov A.N., Zhavoronok S.I., Kurbatov A.S., Rabinskiy L.N., Tushavina O.V. Main problems in the creation of thermal-protection systems based on structurally hete­rogeneous materials and the methods of their solution: A Review. High Temperature. 2021;59(2-6):346–372. https://doi.org/10.1134/S0018151X21020012

2. Ren X., Wang W., Sun K., Hu Y., Xu L., Feng P. Preparation of MoSi2-modified HfB2–SiC ultra high temperature ceramic anti-oxidation coatings by liquid phase sintering. New Carbon Materials. 2022;37(3):603–614. https://doi.org/10.1016/S1872-5805(21)60060-4

3. Fu Q.-G., Li H.-J., Wang Y.-J., Li K.-Z., Wu H. A MoSi2–SiC–Si/MoSi2 coating to protect carbon/carbon compo­sites against oxidation at 1700 °С. Surface Review and Letters. 2009;16(3):437–440. https://doi.org/10.1142/S0218625X09012822

4. Zhang P., Fu Q., Cheng C., Zhu X., Huang J., Zhang J., Li W. Comparing oxidation behaviors at 1773 K and 1973 K of HfB2–MoSi2/SiC–Si coating prepared by a combination method of pack cementation, slurry painting and in-situ synthesis. Surface & Coatings Technology. 2022;403:126418. https://doi.org/10.1016/j.surfcoat.2020.126418

5. Astapov A.N., Matulyak A.I. Reaction synthesis for producing MoSi2-based coatings. Russian Metallurgy (Metally). 2022;(12):1569–1577. https://doi.org/10.1134/S0036029522120059

6. Fang H.-T., Zhu J.-C., Yin Z.-D. A Si–Mo fused slurry coa­ting for oxidation protection of carbon-carbon composites. Journal of Materials Science Letters. 2001;20:175–177. https://doi.org/10.1023/A:1006747915037

7. Zhao J. SiC/Si–MoSi2/MoSi2 oxidation protective coating for carbon material at 1700 °С. Advanced Materials Research. 2010;160-162:1–6. https://doi.org/10.4028/www.scientific.net/AMR.160-162.1

8. Jiang Y., Ye C., Ru H., Wang W., Zhang C., Yue X. Oxidation protective MoSi2–SiC–Si coating for graphite mate­rials prepared by slurry dipping and vapor silicon infiltration. Ceramics International. 2018;44(5):5171–5178. https://doi.org/10.1016/j.ceramint.2017.12.122

9. Cai Z., Zhang D., Chen X., Huang Y., Peng Y., Xu C., Huang S., Pu R., Liu S., Zhao X., Xiao L. A novel ultra-high-temperature oxidation protective MoSi2–TaSi2 ceramic coating for tantalum substrate. Journal of the European Ceramic Society. 2019;39:2277–2286. https://doi.org/10.1016/j.jeurceramsoc.2019.02.037

10. Wang P., Li H., Ren X., Yuan R., Hou X., Zhang Y. HfB2–SiC–MoSi2 oxidation resistance coating fabricated through in-situ synthesis for SiC coated C/C composites. Journal of Alloys and Compounds. 2017;722:69–76. https://doi.org/10.1016/j.jallcom.2017.06.008

11. Bannykh D., Utkin A., Baklanova N. Effect of chromium additive on sintering and oxidation behavior of HfB2–SiC ceramics. Ceramics International. 2018;44:12451–12457. https://doi.org/10.1016/j.ceramint.2018.04.035

12. Bannykh D., Utkin A., Baklanova N. The peculiarities in oxidation behavior of the ZrB2–SiC ceramics with chromium additive. International Journal of Refractory Metals and Hard Materials. 2019;84:1–23. https://doi.org/10.1016/j.ijrmhm.2019.105023

13. Saito N., Ikeda H., Yamaoka Y., Glaeser A.M., Nakashima K. Wettability and transient liquid phase bonding of hafnium diboride composite with Ni–Nb alloys. Journal of Materials Science. 2012;47(24):8454–8463. https://doi.org/10.1007/s10853-012-6778-3

14. Khanra A.K., Godkhindi M.M. Effect of Ni additives on pressureless sintering of SHS ZrB2 . Advances in Applied Ceramics. 2005;104(6):273–276. https://doi.org/10.1179/174367606X69898

15. Zheng Q., Gu H., Hu D.-L., Zhang G.-J. Transient li­quid-phase to guide multiphase evolution in reactive-hot-pressed ZrB2–SiC–ZrC ceramics. Journal of Materiomics. 2020;6:607–617. https://doi.org/10.1016/j.jmat.2020.05.001

16. Bannykh D.A., Lozanov V.V., Baklanova N.I. Interaction of HfB2 + SiC + Cr mixtures of various compositions with carbon and silicon carbide substrates. Inorganic Mate­rials. 2021;57:343–350. https://doi.org/10.1134/S0020168521040026

17. Astapov A.N., Belokopytova E.S., Matulyak A.I., Pogodin V.A., Soldatenko I.V. Preparation of the coating on the C/C–SiC composite from the Mo–HfSi2–SiB4 composition by the in situ reaction synthesis. Russian Metallurgy (Metally). 2024;2024(3):681–689. https://doi.org/10.1134/S003602952470112X

18. Korniyenko K., Velikanova T., Rogl P. B–Mo–Si ternary phase diagram evaluation. Landolt-Börnstein – Group IV: Physical Chemistry. 2010;11E2:19–45. https://doi.org/10.1007/978-3-642-02700-0_3

19. Bale C.W., Chartrand P., Degterov S.A., Eriksson G., Hack K., Mahfoud R. Ben, Melançon J., Pelton A.D., Petersen S. FactSage thermochemical software and databases. Calphad. 2002;26(2):189–228. https://doi.org/10.1016/s0364-5916(02)00035-4

20. Physical quantities: Handbook (Eds. I.S. Grigor’ev, E.Z. Meylihov. Moscow: Energoatomizdat, 1991. 1232 p. (In Russ.).

21. Zhang B., Wub L., Li Zh. Predicted structural evolution and detailed insight into configuration correlation, mechanical properties of silicon-boron binary compounds. RSC Advances. 2017;7:16109–16118. https://doi.org/10.1039/c7ra00592j

22. Predel B. Hf–Si (Hafnium-Silicon). Landolt-Börnstein – Group IV: Physical Chemistry. 1996;5F:1–2. https://doi.org/10.1007/10501684_1604

23. Zhao J.C., Bewlay B.P., Jackson M.R., Chen Q. Hf–Si binary phase diagram determination and thermodynamic modeling. Journal of Phase Equilibria. 2000;21(1):40–45. https://doi.org/10.1361/105497100770340408

24. Cai G.M., Zheng F., Yi D.Q., Chen H.M., Zhou S.X., Long Z.H., Jin Z.P. Experimental investigation and thermodynamic modeling of Hf–Si–B system. Journal of Alloys and Compounds. 2010;494(1-2):148–154. https://doi.org/10.1016/j.jallcom.2010.01.050

25. Tremblay R., Angers R. Preparation of high purity SiB4 by solid-state reaction between Si and B. Ceramics International. 1989;15(2):73–78. https://doi.org/10.1016/0272-8842(89)90017-5

26. CRC Handbook of Chemistry and Physics: 104th ed. Ed. J.R. Rumble. CRC Press: Taylor & Francis Group, 2023. 1580 p.

27. Low R.J., Robertson I.M., Schaffer G.B. Excessive poro­sity after liquid-phase sintering of elemental titanium powder blends. Scripta Materialia. 2007;56(10);895–898. https://doi.org/10.1016/j.scriptamat.2007.01.040

28. Astapov A.N., Pogodin V.A., Sukmanov I.V., Zhestkov B.E., Prokofiev M.V. Development of Cf/C-UHTC composite and study of its resistance to oxidation and ablation in high-speed high-enthalpy air plasma flow. International Journal of Lightweight Materials and Manufacture. 2024;7(3):362–377. https://doi.org/10.1016/j.ijlmm.2024.02.003