الفهرس 
AcknowledgementOnly 14 pages are availabe for public view
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Abstract
Mo-base found other cracks
Ni- and Fe-base alloys are favored for use in industrial applications because they form chromia scale which are highly corrosion resistant. Some Ni-base alloys also contain aluminum which oxidizes internally. The formed alumna is useful for establishing the protective surface layer of chromia. Oxidation does not present a problem for Ni-base alloys provided that operating temperatures are maintained at appropriate levels. The additives in Ni-base alloys play an influenced role in hot corrosion. Addition of Ni to Fe-base alloys results in its withstanding high temperature oxidation and its content in the alloy has a great effect on the corrosion rate.
In this thesis, the performance of Ni- and Fe-base alloys in an atmosphere of arsenic vapor was studied. Hastelloy X, Inconel 617, Inconel 600, and MA 754 were tested
o
as Ni-base alloys. The corrosion temperature was 650 C or
o
700 C. It was found that increasing the Ni content in Ni-base
alloys resulted in increasing the wt. gain %. Ni is the main constituent element in the scale. Cr does not form a protective layer as that for oxidation. Increasing Fe concentration in the subscale is accompanied by decreasing the As concentration and vice versa.
Fe-base alloys were tested in As atmosphere for 10, 20,
o
and 30 days at 700 C. The formed scale on Incoloy 800-H was
changed into powder as a result of corrosion in As atmosphere. The first subscale of the corroded layer was a porous type. When the corrosion time was increased into 20 days this porous subscale disappeared but the formed layer as a result of corrosion for 30 days as 2 cycles, the first one for 10 days and the second one for 20 days, contained the porous subscale. The corrosion of MA 956 and Fecraloy had the same corrosion mechanism.
Samples of a rZM alloy were investigated as a alloy in As atmosphere for 10, 20, and 30 days. It was that spallation of corroded layer was higher than the types of alloys and the formed layer had perpendicular to the sample surface.
Mixed ceramics (AIN, BN, and TiB), boron nitride, and 2
titanium diboride were also investigated as different types of ceramics. The samples were also spalled off and internal
corrosion was obvious.
Chemical Vapor Deposition, CVD, methods constitute a highly versatile and flexible procedure of applying coating of the refractory metals and nonmetals. TiN in the form of thin protective and/or decorative coating. TiN films were deposited on stainless steel samples. TiCI, Hand N were
” 2 2 ’
the reacting gases used. X-Ray diffraction revealed the
o
growth of crystalline TiN with a = 4.24 A. It was also
o
’i,J2)gnd that the deposition on polished samples may result in a ’L~siting of preferred orientation crystals.