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INFLUENCE OF RHENIUM ON THE HEAT RESISTANCE OF THE ALLOY OF COBALT WITH NIOBIUM CARBIDE H. P. Dmytrieva,1, 2 Т. S. Cherepova,1 Т. А. Kosorukova,1 and Т. V. Pryadko1

UDC 669 018.28.225: 620.193.22

By the methods of physicochemical analysis, we study the influence of 1–9 wt.% of rhenium on the melting temperature, structure, and heat resistance of the industrial KhTN-62 cast alloy used for wear protection of the contact surfaces of working blades of gas-turbine engines. It was established that, for the optimal rhenium content varying from 3 to 9 wt.%, the oxidation resistance of the alloy at 1100°C becomes twice higher. In this case, the melting temperature of the alloy remains not lower than 1300°C, its structure does not change, and therefore, it is quite promising for application under severe operating conditions of gas-turbine engines. Keywords: cobalt, niobium carbide, eutectic, industrial KhTN-62 alloy, rhenium, heat resistance, melting temperature, structure.

Introduction In the structures of turbines of contemporary gas-turbine engines (GTE), it is customary to use blades with shroud platform with special contact areas on the lateral end faces aimed at guaranteeing the stiffness of their connection after mounting in a wheel. The damage to shroud platforms is one of the main factors restricting the lifetime of blades and engines as a whole. It is possible to efficiently increase the duration of operation of the blades by applying wear-resistant materials to the contact surfaces of shroud platforms. For this purpose, the Institute of Metal Physics, together with the “Іvchenko-Prohres” State Enterprise, on the basis of their own results of investigations of the phase equilibria in alloys of the С–Со–Nb system and the conditions of crystallization of alloy with eutectic composition in a Со–NbC quasibinary cross section [1], created industrial alloys wear-resistant at temperatures ≥ 1000°С, namely, the KhTN-61 alloy guaranteeing the service life of the engine greater than 6000 h [2] and its more heat-resistant analog (KhTN-62) [3]. These alloys are used in the as-cast state and do not require thermal treatment. They are applied for the production of new and restoration of old engines for the АN-124, АN-225, and АN-148 aircrafts. These alloys are also used at the other plants of the “Іvchenko-Prohres” State Enterprise and “Motor Sich” JSC [4, 5]. In the process of development of the spacecraft and aircraft industries, the conditions of operation of GTE become more severe and, hence, the plants are interested in the improvement of alloys and, in particular, in elevation of their heat resistance with preservation of the high-temperature wear resistance. In the present work, we determine the influence of additional doping of the industrial KhTN-62 alloy with rhenium aimed at increasing its oxidation resistance at 1100°С with the preservation of melting temperature on a level not lower than 1300°С, its structure, and phase state. 1 2

Kurdyumov Institute of Metal Physics, Ukrainian National Academy of Sciences, Kyiv,