Control of carbon content and properties of WC–6Co cemented carbide using different plasticizers and carbon black or graphite additives

Different plasticizers and free-carbon additives, can be used not only to improve the formability and compactability of cemented carbide blanks but also to control carbon content. This study examined the effect of plasticizer content of 1, 2, and 4 % for rubber, PEG-4000, and paraffin, as well as graphite and carbon black additives, on the phase composition, density, porosity, hardness, and fracture toughness of products obtained from a WC–6Co powder mixture with insufficient carbon content. An increase in rubber content by 1 % increased the carbon content by 0.2 %. The addition of carbon black and graphite resulted in an equivalent increase in carbon content. Graphite is unsuitable for increasing carbon content because it is distributed unevenly throughout the sample volume, which reduces the material properties. Paraffin and polyethylene glycol used as plasticizers did not cause noticeable changes in carbon content or in the phase and chemical composition of the resulting cemented carbide products. Empirical relationships were developed to predict the carbon content, phase composition, density, hardness, and fracture toughness of the resulting cemented carbide products depending on the initial carbon content and the content of plasticizers or added carbon black. Relationships were also established describing the increase in hardness with increasing η-phase content and the decrease in hardness with increasing free-carbon content. The use of 1 % rubber as a plasticizer and 0.1 % carbon black as an additive compensated for the carbon deficiency of 0.39 % in the medium-grained WC–6Co cemented carbide blanks and increased fracture toughness from 8.4 MPa·m^1/2 for the alloy without a plasticizer to 12.2 MPa·m^1/2 with rubber and 12.7 MPa·m^1/2 with carbon black. High hardness was retained in both cases, with HV values of 1420 and 1410, respectively.

1. Dvornik M.I., Mikhailenko E.A., Shichalin O.O., Buravlev I.Yu., Burkov A.A., Vlasova N.M., Chernyakov E.V., Khe V.K., Chigrin P.G. Grain contiguity of tungsten carbide and hardness of nanostructured and ultrafine-grained WC–(Co)–VC–Cr3C2 cemented carbides fabricated by spark plasma and liquid phase sintering. Powder Metallurgy аnd Functional Coatings. 2025;19(2):51–61. https://doi.org/10.17073/1997-308X-2025-2-51-61

2. Dvornik M.I., Mikhailenko E.A., Burkov A.A., Chernyakov E.V. Investigation of the properties of WC–5TiC–10Co cutting inserts produced using a 3D-printed plastic mold. Powder Metallurgy аnd Functional Coatings. 2024;18(5):55–65. https://doi.org/10.17073/1997-308X-2024-5-55-65

3. Panov V., Shumenko V. Technology and properties of sintered hard alloys. Moscow: Izd-vo MISIS, 2013. 144 p. (In Russ.).

4. Nie H., Zhang T. Development of manufacturing techno­logy on WC–Co hardmetals. Tungsten. 2019;1(3):198–212. https://doi.org/10.1007/s42864-019-00025-6

5. Zhadyaev A.A., Novikov V.A., Khakimov A.M., Amo­sov A.P. Determining the cause of microstructure defects of WC–Cо carbon alloy products in production. Sovremennye materialy, tekhnika i tekhnologii. 2020;6(33): 21–28. (In Russ.).

6. Shi X., Yang H., Wang S., Shao G., Duan X. Influences of carbon content on the properties and microstructure of ultrafine WC–10Co cemented carbide. Journal of Wuhan University of Technology-Material Science. 2007;22(3):473–477. https://doi.org/10.1007/s11595-006-3473-8

7. Delanoë A., Lay S. Evolution of the WC grain shape in WC–Co alloys during sintering: Effect of C content. International Journal of Refractory Metals and Hard Mate­rials. 2009;27(1):140–148. https://doi.org/10.1016/j.ijrmhm.2008.06.001

8. Gu L., Huang J., Xie C. Effects of carbon content on microstructure and properties of WC–20Co cemented carbides. International Journal of Refractory Metals and Hard Materials. 2014;(42):228–232. https://doi.org/10.1016/j.ijrmhm.2013.09.010

9. Wang H., Song X., Liu X., Gao Y., Wei C., Wang Y., Guo G. Effect of carbon content of WC–Co composite powder on properties of cermet coating. Powder Techno­logy. 2013;246:492–498. https://doi.org/10.1016/j.powtec.2013.06.012

10. Kim S., Han S.-H., Park J.-K., Kim H.-E. Variation of WC grain shape with carbon content in the WC–Co alloys during liquid-phase sintering. Scripta materialia. 2003;48(5):635–639. https://doi.org/10.1016/S1359-6462(02)00464-5

11. Lantsev E.A., Chuvil’deev V.N., Nokhrin A.V., Bol­din M.S., Tsvetkov Yu.V., Blagoveshchenskiy Yu.V., Isaeva N.V., Andreev P.V., Smetanina K.E. Kinetics of spark plasma sintering of WC–10%Co ultrafine-grained hard alloy. Fizika i khimiya obrabotki materialov. 2019;(6): 36–51 (In Russ.). https://doi.org/10.30791/0015-3214-2019-6-36-51

12. Krasovskii P.V., Blagoveshchenskii Yu.V., Grigoro­vich K.V. Determination of oxygen in W–C–Co nanopowders. Inorganic Materials. 2008;44(9):954–959. (In Russ.). https://doi.org/10.1134/S0020168508090100

13. Zaitsev A.V. Physico-chemical analysis of the processes of obtaining nanodisperse WC–Co powders and improving their sintering technology. Diss. Cand. (Eng.). St. Petersburg: Peter the Great St. Petersburg Polytechnic University, 2016. (In Russ.).

14. Yang Y., Luo L. M., Zan X., Zhu X. Y., Zhu L., Wu Y.C. Study on preparation and properties of WC–8Co cemented carbide doped with rare earth oxide. International Journal of Refractory Metals and Hard Materials. 2021;98:105536. https://doi.org/10.1016/j.ijrmhm.2021.105536

15. Qian C., Liu Y., Cheng H., Li K., Liu B., Zhang X. The effect of carbon content on the microstructure and mechanical properties of cemented carbides with a CoNiFeCr high entropy alloy binder. Materials. 2022;15(16):5780. https://doi.org/10.3390/ma15165780

16. Straumal B., Konyashin I. WC-based cemented carbides with high entropy alloyed binders: A review. Metals. 2023;13(1):171. https://doi.org/10.3390/met13010171

17. Lantsev E.A., Nokhrin A.V., Boldin M.S., Popov A.A. The influence of C content on the spark pulse plasma sintering of WC–Co. In: III International conference of young scientists on modern problems of materials and structures (24–28 August 2019). Ulan-Ude: Buryatskii gosudarstvennyi universitet imeni Dorzhi Banzarova, 2019. P. 82–86 (In Russ.).

18. Fries S., Burkamp K., Broeckmann C., Richter S., Westermann H., Süess B. Influence of carbon content on fatigue strength of cemented carbides. International Journal of Refractory Metals and Hard Materials. 2022;105:105823. https://doi.org/10.1016/j.ijrmhm.2022.105823

19. Tang Y., Wang S., Xu F., Hong Y., Luo X., He S., Chen L., Zhong Z., Chen H., Xu G., Yang Q. Effect of carbon content on the properties of inhomogeneous cemented carbides with fine-grained structures produced via one-step transformation. Journal of Alloys and Compounds. 2021;882:160638. https://doi.org/10.1016/j.jallcom.2021.160638

20. Dvornik M.I., Mikhailenko E.A. Production of WC–15Co ultrafine-grained hard alloy from powder obtained by VK15 alloy waste spark erosion in water. Powder Metal­lurgy аnd Functional Coatings. 2020;15(3):4–16. (In Russ.). https://doi.org/10.17073/1997-308X-2020-3-4-16

21. Dvornik M.I., Zaitsev A.V., Mikhailenko E.A. The distribution of carbon in a tungsten–cobalt alloy during heat treatment in a gaseous medium of carbon oxides. Theoretical Foundations of Chemical Engineering. 2019;53(5): 916–920. https://doi.org/10.1134/S0040579518050081

22. Dvornik M.I., Mikhaylenko E.A. Control of carbon content in ultrafine cemented carbide by heat treatment in reducing atmospheres containing carbon oxides. Journal of Materials Engineering and Performance. 2018;27(7): 3610–3618. https://doi.org/10.1007/s11665-018-3460-1

23. Konyashin I., Ries B., Lachmann F., Fry A. A novel sintering technique for fabrication of functionally gradient WC–Co cemented carbides. Journal of Materials Science. 2012;47(20):7072–7084. https://doi.org/10.1007/s10853-012-6516-x

24. Parker S.R., Whiting M.J., Yeomans J.A. Control of carbon content in WC–Co hardmetal by heat treatment in reducing atmospheres containing methane. International Journal of Refractory Metals and Hard Materials. 2017;66:204–210. https://doi.org/10.1016/j.ijrmhm.2017.02.009

25. Kanerva U., Karhu M., Lagerbom J., Kronlöf A., Honkanen M., Turunen E., Laitinen T. Chemical synthesis of WC–Co from water-soluble precursors: The effect of carbon and cobalt additions to WC synthesis. International Journal of Refractory Metals and Hard Materials. 2016;56:69–75. https://doi.org/10.1016/j.ijrmhm.2015.11.014

26. Wei C., Song X., Fu J., Lv X., Wang H., Gao Y., Zhao S., Liu X. Effect of carbon addition on microstructure and properties of WC–Co cemented carbides. Journal of Materials Science & Technology. 2012;28(9):837–843. https://doi.org/10.1016/S1005-0302(12)60140-6

27. Li X., Zhang X., Zhang J., Zhang Q., Ji V., Liu J. Effect of Mo and C additions on eta phase evolution of WC–13Co cemented carbides. Coatings. 2022;12(12):1993. https://doi.org/10.3390/coatings12121993

28. Suetin D.V., Shein I.R., Ivanovskii A.L. Structural, electronic and magnetic properties of η carbides (Fe3W3C, Fe6W6C, Co3W3C and Co6W6C) from first princip­les calculations. Physica B: Condensed Matter. 2009; 404(20):3544–3549. https://doi.org/10.1016/j.physb.2009.05.051

29. Lee H.C., Gurland J. Hardness and deformation of cemented tungsten carbide. Materials Science and Engineering. 1978;33(1):125–133. https://doi.org/10.1016/0025-5416(78)90163-5

30. Dvornik M.I., Zaitsev A.V. Variation in strength, hardness, and fracture toughness in transition from medium-grained to ultrafine hard alloy. Russian Journal of Non-Ferrous Metals. 2018;59(5):563–569. https://doi.org/10.3103/S1067821218050024

31. Bonache V., Rayón E., Salvador M.D., Busquets D. Nanoindentation study of WC–12Co hardmetals obtained from nanocrystalline powders: Evaluation of hardness and modulus on individual phases. Materials Science and Engineering: A. 2010;527(12):2935–2941. https://doi.org/10.1016/j.msea.2010.01.026