An investigation into the external friction of niobium and tantalum carbides at high temperatures in vacuum
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An investigation was carried out into the temperature dependence of external friction between specimens made from NbC0.98 and also between specimens made from TaC0.97 in the temperature range extending from room temperature to 1800°C in a vacuum of 10−5 mm Hg.
The coefficient of friction of niobium carbide has its minimum at 1200°C and that of tantalum carbide at 1300°C. Above this temperature a sharp increase in the coefficient of friction is observed. The reason for this increase is an intense adhesion interaction between contact surfaces.
It was found that the loading of a static contact surface between the materials under investigation at high temperatures produces creep processes controlled by transverse slip of dislocations with a considerable contribution from the diffusion mechanism. The creep activation energy in the temperature range 1300–1500°C is 1.3 eV for NbC and 1.4 eV for TaC.
It was shown that the slip activation energy is determined mainly by the presence of convalent bonds in pure materials and compounds.
KeywordsCarbide Activation Energy Niobium Contact Surface Tantalum
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