ПОРІВНЯЛЬНИЙ АНАЛІЗ КОМПЛЕКСУ ВЛАСТИВОСТЕЙ ЖАРОМІЦНИХ НІКЕЛЕВИХ СПЛАВІВ

Purpose. To conduct comparative studies of the complex of physico-mechanical properties of the imported alloy N-155 and the domestic alloy ЗМІ-11 in order to increase the service life of the rotating blades. To conduct comparative tests on the short-term and long-term strength of the alloys in the initial state (after heat treatment), to conduct comparative tests on the short-term and long-term strength of the alloys after prolonged thermal action at  T = 850 °C, 950 °C for 1000, 3000, 5000 hours and to conduct research by metallographic method and micro-X-ray spectral analysis of the microstructure and phase composition of the alloys. Research methods. Alloy samples were made from ingots weighing 10 kg in a vacuum induction furnace УППФ-3M in an argon environment at a pressure of 1.4–5.3 Pa in crucibles with the main lining with simultaneous pouring of samples of equiaxed crystallization. Chemical analysis was carried out by standard methods in accordance with the requirements of TU 14-1689-73 and OST 1.90127-85. Microstructure studies were carried out on microsections, the plane of which was oriented normal to the surface on a light optical microscope “Olympus IX-70” with a digital video camera “ExwaveHAD color video camera Digital Sony” at magnifications ×200, ×500, ×1000. Strength tests (GOST 1497-61, GOST 9651-61, GOST 1497-84) were carried out on standard cylindrical samples (diameter of the working part 5 mm, length 25 mm) at temperatures 200, 800, 900 and 1000°C on a УМЕ-10TM brand tensile machine. Long-term strength tests (GOST 10145-81) were carried out on standard cylindrical samples at temperatures 800, 900, 10000 °C and corresponding loads 600, 400, 180 MPa on an AIMA-5-2 machine. Obtained results. It was found that during tests at 800 and 900°С, the tensile strength of the N-155 alloy is 1.2 times lower than that of ЗМІ-11, and the long-term strength is 5.2 times lower, respectively. It was shown that the amount of the strengthening phase in the ЗМІ-11 alloy is 6…10 % more, evenly distributed throughout the alloy body. It was established that in the composition of the strengthening phase of the ЗМІ-11 alloy, the concentration of chromium, tungsten, and molybdenum remains practically unchanged and does not depend on the presence of niobium. At the same time, in the composition of the strengthening phase of the ЗМІ-11 alloy, the concentration of cobalt increases by             1.4 times, and the concentration of aluminum and titanium decreases by 1.1 times compared to the N-155 alloy. It was established that in the process of dissolving non-equilibrium eutectic precipitates, microvolumes arise, locally supersaturated with tungsten, chromium, and titanium, in which the probability of the formation of carbides on a more complex basis increases. It was found that during prolonged thermal action carbides based on tantalum TaC and on a mixed basis (Ta, Ti) C in the ЗМІ-11 alloy are thermally more stable than carbides in the N-155 alloy. Scientific novelty. The obtained results allow us to understand the thermodynamics of phase formation processes in two alloying systems and to establish the relationships between alloying elements concentration and the phase composition of the alloy. Practical value. The obtained results allow us to recommend the domestic ЗМІ-11 as a substitute for the foreign alloy N-155 without loss of properties and service life.