Chemical composition and structure of interfacial boundaries in Cr₃C₂-Ti powder hard alloys after explosive pressing and subsequent heating

The paper presents the results of studies of the fine structure, chemical and phase composition of boundaries between the components of the Cr₃C₂-Ti hard alloy containing 40 wt.% of titanium bond in the state after explosive pressing, as well as after heat treatment. The powder mixture was subjected to shock-wave loading at a heating temperature of 730 °C and pressure of 14 GPa to ensure the maximum compaction and consolidation of the powder mixture without sintering. Compact specimens were heat-treated by heating from 400 to 700 °С and holding in the oven for 1 hour followed by still air cooling. The equilibrium phase composition was calculated by numerical thermodynamic modeling using Thermo-Calc software. The structure and elemental composition were studied using FEI Quanta 3D and Versa 3D electron microscopes with an integrated focused ion beam system for foil fabrication, as well as FEI Tecnai G2 20F and Titan 80-300 transmission electron microscopes with foil transmission scanning mode. The Bruker D8 Advance diffractometer was used for X-ray phase analysis. It was shown that the formation of strong interfacial boundaries under explosive pressing of titanium and chromium carbide powder mixtures is accompanied by chemical interaction between the components with the formation of boundary layers having a total thickness of about 90 nm. There is a continuous monotonic change in the Cr and Ti content within the transition layer at the almost constant carbon content. The phase composition of layers corresponds to the equilibrium one calculated at the shock-wave compression pressure but it is thermodynamically nonequilibrium under normal conditions. When heated to 400 °C, boundary layers dissolve with the transition of Cr₃C₂-Ti hard alloys into a two-phase state. When heated to 700 °C, alternating layers of carbon-depleted chromium carbides (Cr₇C₃, Cr₂₃C₆) and titanium carbide (TiC) form along the interfacial boundaries by carbon diffusion from the original chromium carbide (Cr₃C₂) to titanium.

1. Nesterenko V.F. Dynam1cs of heterogeneous materials. New York: Springer Sc1ence, 2001.

2. Rogozin V.D. Explosive treatment of powder materials. Volgograd: Politekhnik, 2002 (In Russ.).

3. Prummer R. Explosive compaction of powders and composites. Boca Raton: CRC Press, 2006.

4. Krokhalev A.V., Kharlamov V.O., Kuz'min S.V., Lysak V.I, Pai V.V. Explosive compaction of chromium carbide powders with a metallic binder. Combustion, Explosion and Shock Waves. 2019. Vol. 55. No. 4. P. 491—499.

5. Ageev E.V., Latypov R.A., Ageeva E.V. Investigation into the propert1es of electroerosion powders and hard alloy fabricated from them by isostatic pressing and sintering. Izvestiya Vuzov. Tsvetnaya Metallurgiya (Universities' Proceedings Non-Ferrous Metallurgy). 2014. No. 6. P. 51—55 (In Russ.).

6. Panov V.S., Zaitsev A.A. Development trends of technology of ultrafine and nanosized hard alloys WC—Co. Izvestiya Vuzov. Poroshkovaya Metallurgiya i Funktsional'nye Pokrytiya (Universities’ Proceedings. Powder Metallurgy and Functional Coatings). 2014. No. 3. С. 38—48 (In Russ.).

7. Kear B.H., Skandan G., Sadangi R.K. Factors controlling decarburization in HVOF sprayed nano-WC/Co hard coatings. Scripta Mater. 2001. Vol. 44. No. 8-9. P. 1703—1707.

8. Kalita V.I., Radyuk A.A., Komlev D.I., Ivannikov A.Yu., Blagoveshchenskii Yu.V., Grigorovich K.V., Shibaeva T.V., Umnova N.V., Molokanov V.V., Umnov P.P., Mel’nik Yu.I. Mechanically alloy powder plasma WC—Co coatings. Fizika i khimiya obrabotki materialov. 2014. No. 5. P. 22—29 (In Russ.).

9. Mrdak M.R. Mechan1cal propert1es and microstructure of vacuum plasma sprayed СгзС2—25 (Ni20Cr) coatings. Vojnotehnickiglasnik. 2015. Vol. 63. No. 2. P. 47—63.

10. Pirso J., Viljus M. Structure formation of CrзC2-based cermets during sintering. Proceedings of Powder Metallurgy World Congress. 2000. P. 1265—1268.

11. Duran C., Eroglu S. Liquid-phase sintering and properties of Cr3С2/NiCr cermets. J. Mater. Proces. Technol. 1998. Vol. 74. No. 1-3. P. 69—73.

12. Al’tshuler L.V., Trunin R.F., Urlin V.D., Fortov V.E., Funtikov A.I. Development of dynamic h1gh pressure research methods 1n Russ1a. Uspekhi fizicheskikh nauk. 1999. Vol. 169. No. 3. P. 323—344 (In Russ.).

13. Lee S.H., Hokamoto K. WC/Co coating on a mild steel substrate through underwater shock compact1on us1ng a self combustible material layer (WC/Co coating through underwater shock compaction). Mater. Trans. 2007. Vol. 48. No. 1. P. 80—83.

14. Yakovlev I.V., Ogolikhin V.M., Shemelin S.D. Explosive manufacturing of ceramic-metal protective containers. Vestnik Permskogo natsional'nogo issledovatel'skogo politekhnicheskogo universiteta. Mashinostroenie, materialovedenie. 2012. Vol. 14. P. 55—60 (In Russ.).

15. Buzyurkin A.E., Kraus E.I., Lukyanov Y.L. Explosive compaction of WC + Co mixture by axisymmetric scheme. Journal of Physics: Conf. Ser. 2015. Vol. 653. No. 1. P. 012036.

16. Krokhalev A.V., Kharlamov V.O., Tupitsin M.A., Kuz'min S.V., Lysak V.I. Revisiting the possibility of formation of hard alloys from powder mixtures of carbides with metals by explosive compacting without sintering. Russ. J. Non-Ferr. Met. 2018. Vol. 59. No. 5. P. 550—556.

17. Bondar' M.P., Nesterenko V.F. Contact deformation and bonding criteria under impulsive loading. Combustion, Explosion and Shock Waves. 1991. Vol. 27. Iss. 3. P. 364—376.

18. Bondar' M.P. Explosive compaction: the type of microstructure of contact boundaries produced by formation of a strong bond. Combustion, Explosion and Shock Waves. 2004. Vol. 40. Iss. 4. P. 489—497.

19. Bondar' M.P., Obodovskii E.S., Psakh'e S.G. A study into the microstructure features of the zone of contact interaction between powder particles at dynamic pressing. Fizicheskaya mezomekhanika. 2004. Vol. 7. No. 3. P. 17—23 (In Russ.).

20. Krokhalev A.V, Kharlamov V.O., Kuz'min S.V., Lysak V.I. Foundations of the fabrication technology of wearresistant coatings made of mixtures of chromium carbide powders with a metallic binder by explosive pressing. Russ. J. Non-Ferr. Met. 2018. Vol. 59. Iss. 4. P. 419—432.

21. Tkachenko Yu.G. Friction and wear of oxygen-free refractory compounds and materials based on them at high temperatures. Trenie i iznos. 1981. Vol. 2. No. 5. P. 864— 876 (In Russ.).

22. Lysak V.I., Kuz'min S.V., Krokhalev A.V., Grinberg B.A. Structure of boundaries in composite materials obtained using explosive loading. Physics of Metals and Metallography. 2013. Vol. 114. No. 11. P. 947—952.

23. Wang D.Y., Weng K.W., Chang C.L., Ho W.Y. Synthesis of Cr3C2 coatings for tribological applications. Surf. Coat. Technol. 1999. Vol. 120. P. 622—628.

24. Li J.F., Huang J.Q., Zhang Y.F., Ding C.X. Tribological properties of plasma-sprayed coatings under water-lubricated sliding. J. Inorg. Mater. 1998. Vol. 13. No. 4. P. 519—520.

25. Lysak V.I., Krokhalev A.V., Kuz'min S.V., Rogozin V.D., Kaunov A.M. Explosive pressing of powders. Moscow: Mashinostroenie, 2015 (In Russ.).

26. Konyashin I., Sologubenko A., Weirich T., Ries B. Complexion at WC—Co grain boundaries of cemented carbides. Mater. Lett. 2017. Vol. 187. P. 7—10.

27. Konyashin I., Straumal B.B., Ries B., Bulatov M.F., Kolesnikova K.I. Contact angles of WC/WC grain boundaries with binder in cemented carbides with various carbon content. Mater. Lett. 2017. Vol. 196. P. 1—3.

28. Konyashin I., Zaitsev A.A., Sidorenko D., Levashov E.A., Ries B., Konischev S.N., Sorokin M., Mazilkin A.A., Herrmann M., Kaiser A. Wettability of tungsten carbide by liquid binders in WC—Co cemented carbides: Is it complete for all carbon contents? Int. J. Refract. Met. Hard Mater. 2017. Vol. 62. P. 134—148.

29. Konyashin I., Zaitsev A., Meledin A., Mayer J., Loginov P., Levashov E., Ries B. Interfaces between model Co—WC alloys with various carbon contents and tungsten carbide. Materials. 2018. Vol. 11. No. 3. 404.