OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 26 No. 2 2024 Oxidation temperatures of WC-Co cemented tungsten carbides Igor Efimovich a, *, Ivan Zolotukhin b Tyumen Industrial University, 38 Volodarskogo, Tyumen, 625000, Russian Federation a https://orcid.org/0000-0002-9060-4988, egor_kosin@mail.ru; b https://orcid.org/0000-0002-1517-9117, zolotuhinis@tyuiu.ru Obrabotka metallov - Metal Working and Material Science Journal homepage: http://journals.nstu.ru/obrabotka_metallov Obrabotka metallov (tekhnologiya, oborudovanie, instrumenty) = Metal Working and Material Science. 2024 vol. 26 no. 2 pp. 199–211 ISSN: 1994-6309 (print) / 2541-819X (online) DOI: 10.17212/1994-6309-2024-26.2-199-211 ART I CLE I NFO Article history: Received: 29 January 2024 Revised: 26 February 2024 Accepted: 20 March 2024 Available online: 15 June 2024 Keywords: Elevated temperatures High-temperature oxidation Tungsten cemented carbides WC-Co Dilatometry Thermal expansion Temperature of oxidation Gas corrosion Chemical destruction ABSTRACT Introduction. Products containing WC-Co cemented tungsten carbides are commonly used in various industries. It is often operates at elevated temperatures, at which, as noted in the literature, tungsten carbides are susceptible to severe oxidation in air. However, no sufficiently accurate values of oxidation temperatures and dependence of these temperatures and the oxidation rate of tungsten carbides on the cobalt content with its wide variation have been established. The subject of the study is the oxidation process of WC-Co cemented tungsten carbides. The purpose of the work is to obtain the oxidation temperatures of WC-Co cemented tungsten carbides with different cobalt content by weight in the range of 3–20 %. Methods. The dynamics of oxidation was studied in air. Specimens of the same length were heated to a temperature of 850 °C and cooled at the same rate in the furnace of a push-rod dilatometer Netzsch 402 PC while its expansion was simultaneously recorded. The oxidation rate of the specimens was determined by the difference in its length before heating and after cooling. The values of oxidation temperatures were obtained by mathematical analysis of relationships of the expansion on temperature. Results and discussion. Experimental dependences of expansion of WC-Co cemented tungsten carbides on temperature in the range from 20 to 850 °C, and for WC-8Co – up to 1,150 °C, were obtained. The oxidation rate of WC-Co cemented tungsten carbides increased linearly with increasing concentration of tungsten carbides (decreased with increasing cobalt content). During heating, two characteristic temperatures were identified: the onset of oxidation (631±4 °C) and the transition to active oxidation (804±11 °C). The established temperatures were the same for different ratios of tungsten carbides and cobalt. The results can be used when choosing temperature conditions for products made from WC-Co cemented tungsten carbides. For citation: Efimovich I.A., Zolotukhin I.S. Oxidation temperatures ofWC-Co cemented tungsten carbides. Obrabotka metallov (tekhnologiya, oborudovanie, instrumenty) = Metal Working and Material Science, 2024, vol. 26, no. 2, pp. 199–211. DOI: 10.17212/1994-6309-2024-26.2199-211. (In Russian). ______ * Corresponding author Efimovich Igor A., Ph.D. (Engineering), Associate Professor Tyumen Industrial University, 38 Volodarskogo, 625000, Tyumen, Russian Federation Tel.: +7 3452 50-49-15, e-mail: egor_kosin@mail.ru Introduction Tool WC-Co cemented tungsten carbides are widely used in various industries. Products containing these alloys are often used in a range of elevated temperatures, which determines the relevance of studying its performance under these conditions. The properties of most materials change significantly as temperature increases, and an increase in chemical activity plays a special role, in particular, when interacting with atmospheric oxygen. The fact of high-temperature oxidation of WC-Co cemented tungsten carbides is confirmed by a number of researchers. The oxidation of WC-Co cemented tungsten carbides is weak up to 600–650 °C [1–3], only cobalt is slightly oxidized [4]. In the temperature range of 650–800 °C, there is a sharp increase in the oxidation rate [3, 5–8], which is confirmed by the curves obtained by the thermogravimetric analysis (TGA). At temperatures above 800 °C, intense oxidation begins. The longer the thermal exposure time (even at constant temperature), the greater the thickness of the oxide layer, which is confirmed by all researchers.
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