OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 26 No. 2 2024 This is apparently due to the properties of the tungsten carbides, which do not significantly depend on the concentration of the cobalt phase. The resulting temperatures of the onset of oxidation (631±4 °C) and the transition to active oxidation (804±11 °C) are in good agreement with the ranges of characteristic temperatures of oxidation obtained by other researchers using methods other than the one used here. Conclusions 1. Oxidation of WC-Co cemented tungsten carbides with a wide variation in cobalt content (Co = 3–20 wt. %) heated to elevated temperatures was studied. 2. After heating in a laboratory furnace to 900 °C, strong oxidation of these tungsten carbides was observed, with the material structure being destroyed. 3. Dilatometric studies resulted in obtaining experimental graphs of the expansion of WC-Co cemented tungsten carbides specimens at temperatures up to 850°C. The graphs have a characteristic hysteresis, indicating permanent elongation due to the presence of oxide layers. The two characteristic temperature ranges of slight expansion and a sharp increase in specimen size are observed. 4. For a specimen with a cobalt content of 8 %, an additional experiment was carried out with heating to 1,150 °C; as a result, it was completely destroyed. 5. The average rate of oxidation of WC-Co cemented tungsten carbides increases with increasing content of tungsten carbides (decreases with increasing cobalt content) and this relationship is linear. 6. Two characteristic temperatures were identified: the onset of oxidation (631±4 °C) and the transition to active oxidation (804±11 °C). These temperatures are the same for different ratios of tungsten carbides and cobalt. References 1. Basu S.N., Sarin V.K. Oxidation behavior of WC-Co. Materials Science and Engineering, 1996, vol. 209 (1–2), pp. 206–212. DOI: 10.1016/0921-5093(95)10145-4. 2. Hidnert P. Thermal expansion of cemented tungsten carbide. Journal of Research of the National Bureau of Standards, 1936, vol. 18, pp. 47–52. Available at: https://nvlpubs.nist.gov/nistpubs/jres/18/jresv18n1p47_A1b.pdf (accessed 04.04.2024). 3. Verkhoturov A.D., Gordienko P.S., Konevtsov L.A., Panin E.S., Potapova N.M. Temperaturnoe okislenie vol’framokobal’tovykh tverdykh splavov [Thermal oxidation of tungsten-cobalt hard alloys]. Perspektivnye materialy = Advanced Materials, 2008, no. 2, pp. 68–75. (In Russian). 4. Chen L., Yi D., Wang B., Liu H., Wu C., Huang X., Li H., Gao Y. The selective oxidation behaviour of WCCo cemented carbides during the early oxidation stage. Corrosion Science, 2015, vol. 94, pp. 1–5. DOI: 10.1016/j. corsci.2015.02.033. 5. Chen L., Wang B., Yi D., Liu H. Non-isothermal oxidation kinetics of WC-6Co cemented carbides in air. International Journal of Refractory Metals and Hard Materials, 2013, vol. 40, pp. 19–23. DOI: 10.1016/j. ijrmhm.2013.02.003. 6. Liu S. Oxidation behavior of WC-Co cemented carbide in elevated temperature. Materials Research Express, 2018, vol. 5 (9). DOI: 10.1088/2053-1591/aad535. 7. Shi X., Yang H., Shao G., Duan X., Wang S. Oxidation of ultrafine-cemented carbide prepared from nanocrystalline WC-10Co composite powder. Ceramics International, 2008, vol. 34, pp. 2043–2049. DOI: 10.1016/j. ceramint.2007.07.029. 8. Gu W.-H., Jeong Y.S., Kim K., Kim J.-C., Son S.-H., Kim S. Thermal oxidation behavior of WC-Co hard metal machining tool tip scraps. Journal of Materials Processing Technology, 2012, vol. 212, pp. 1250–1256. DOI: 10.1016/j.jmatprotec.2012.01.009. 9. Lofaj F., Kaganovskii Y.S. Kinetics of WC-Co oxidation accompanied by swelling. Journal of Materials Science, 1995, vol. 30, pp. 1811–1817. DOI: 10.1007/BF00351615. 10. Bagnall C., Capo J., Moorhead W. Oxidation behavior of tungsten carbide-6% cobalt cemented carbide. Metallography, Microstructure, and Analysis, 2018, vol. 7, pp. 661–679. DOI: 10.1007/s13632-018-0493-7.
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