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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.ruGnidan K.A.
, Graduate student, e-mail:
g.k.a@inbox.ruNovosibirsk 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