Actual Problems in Machine Building 2016 No. 3

Актуальные проблемы в машиностроении. 2016. №3 Материаловедение в машиностроении ____________________________________________________________________ 467 STRUCTURAL FEATURES OF PLASMA COATINGS OF Ni-Cr-Si-B SYSTEM ALLOYED Nb Kornienko E.E., Ph.D. (Engineering), Associate Professor, e-mail: kornienko_ee@mail.ru Gnidan K.A. , Graduate student, e-mail: g.k.a@inbox.ru Novosibirsk State Technical University, 20 Prospekt K. Marksa, Novosibirsk, 630073, Russian Federation Abstract The powders mixture (98 wt. % Ni-Cr-Si-B, 2 wt. % Nb) was coated onto steel tube (0.2 % C) with help air-plasma spraying. The obtained coatings were melted in furnace (heating temperature – 1100 °C, holding time - 10 min, cooling - air). The coatings research was carried out using optical microscopy, scanning electron microscopy and EDS analysis. In the coating before heating the gray interlayers of niobium boride (NbB 2 ) were uniformly distributed on the powder self-fluxing particles boundaries. The melted coatings are characterized by the presence of γ-Ni solid solution dendritic, eutectic of Ni-Ni3B, niobium carbide (NbC), chromium borides (CrB or CrB 2 ) and chromium carbides (Cr 7 C 3 and Cr 23 C 6 ). It was established, that NbC are crystallization centers, from which plates of chromium boride grow in different directions. It was showed that in the coatings alloyed niobium chromium boride plates finer than plates in coatings without Nb. Keywords plasma spraying; alloying, self-fluxing material, Ni-Cr-Si-B