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Journal of Material Sciences
ISSN: 2321-6212
I n t e r n a t i o n a l C o n f e r e n c e o n
Metal, Mining and
Magnetic Materials
N o v e m b e r 0 1 - 0 2 , 2 0 1 8
P a r i s , F r a n c e
Metal and Magnetism 2018
Recent trends in development of high temperature metallic
materials and protective coatings
Sanjib Majumdar
Bhabha Atomic Research Centre, India
M
olybdenum and niobium based metallic materials or composites are being investigated as the potential alternative for high
temperature applications beyond the capability limit of nickel based superalloys. Mo-Si-B alloy comprised with the three
phase microstructure of Moss–Mo5SiB2 (T2)-Mo3Si (A15) is considered as the most promising material for these applications.
The effect of rare earth elements Y and La on oxidation behaviour of Mo-Si-B alloys was studied in detail. These elements promote
the formation of stable yttrium/lanthanum-molybdate phases at the early stages of oxidation. Formation and volatilization of
MoO3 is suppressed and a silica-rich outer scale is formed providing superior protection against oxidation. Mo-Ti-Si alloys of
compositions Mo-40Ti-30Si (in wt %) and Mo-40Ti-10Si were prepared in the form of plates by adopting mechanical alloying and
subsequent reactive hot pressing at 1600 °C. The densities of the alloys were found to be much lower than the conventional alloys
used for high-temperature applications. Oxidation tests of both the alloys were conducted in the temperature range 900-1300 °C
in static air. Alloy Mo-40Ti-30Si showed superior oxidation resistance and the thickness of the oxide layer varied between 2-90
µm depending upon temperature and time of exposure. Mechanical properties of these alloys were compared with respect to
micro or nano hardness measurements of the individual phases. Mo-TZM (Mo-0.5Ti-0.1Zr-0.02C) and Nb-1Zr-0.1C alloys were
produced respectively by powder metallurgy and reduction followed by electron beam melting. Development of microstructure
and evaluation of mechanical properties are studied in detail with varying heat treatment procedure. Silicide and alumino-silicide
based coatings were developed on Mo-Si-B, Mo-Ti-Si, TZM and Nb-1Zr-0.1C alloys. The coated alloys showed superior oxidation
resistance as compared to the bare materials. The detailed microstructural characterization using scanning electron microscopy
(SEM), energy dispersive spectrometry (EDS), electron backscattered diffraction (EBSD) and transmission electron microscopic
(TEM) analysis revealed the formation of different phases in the alloy systems, coating layers and protective oxide scales.
sanjib731@gmail.comJ Mat. Sci. 2018, Volume:6
DOI: 10.4172/2321-6212-C7-033