% IMPORTANT: The following is UTF-8 encoded. This means that in the presence
% of non-ASCII characters, it will not work with BibTeX 0.99 or older.
% Instead, you should use an up-to-date BibTeX implementation like “bibtex8” or
% “biber”.
@PHDTHESIS{TenevaKosseva:60785,
author = {Teneva-Kosseva, Guergana I.},
othercontributors = {Köhne, Heinrich},
title = {{O}xidschichtbildung und {M}aterialprobleme metallischer
{W}erkstoffe bei {V}erbrennungsprozessen mit {H}eizöl {EL}},
address = {Aachen},
publisher = {Publikationsserver der RWTH Aachen University},
reportid = {RWTH-CONV-122475},
pages = {VIII, 171 S. : Ill., graph. Darst.},
year = {2006},
note = {Zsfassung in dt. und engl. Sprache; Aachen, Techn.
Hochsch., Diss., 2005},
abstract = {Scope of the present work was the investigation of the
oxide scale formation on metallic high-temperature alloys
resulting during reaction with the atmosphere of the
combustion of industrial gas oil (IGO). The Ni-Cr-based
alloys 601 (2.4851), 602 (2.4633), 603, 693 and 617 (2.4663)
were tested at elevated temperatures between 900°C and
1050°C in a burner rig equipped with a low-NOx
recirculation burner by application as material of the
burner flame tube. Further on, the oxide scale on a woven
wire cloth made of a Ni-Cr-based alloy was analysed. The
wire cloth was used as the hot surface of a radiant burner
at temperatures of approximately 685°C for an operation
time of 844 h. All alloys investigated in the low-NOx burner
rig showed following oxide scale structure: a chromium oxide
scale at the alloy surface and aluminium or silicon oxide
(on alloy 603) beneath. Particles with a composition similar
to that of the bulk alloy were found enclosed in the
chromium oxide scale. Frequently these particles were
located near the oxide-gas boundary indicating an impending
local degradation of the chromium oxide scale. Aluminium
oxide grew predominantly along grain boundaries in the depth
of the bulk. During the test period of up to 3000 h no
aluminium oxide scale was found. For longer investigation
times accelerated internal oxidation of aluminium was
observed.In contrast to aluminium, silicon formed an albeit
noncontinuous scale of silicon oxide directly below the
chromium oxide layer. The diffusion of chromium towards the
surface was inhibited by the silicon scale, which resulted
in a slower kinetic of the chromium oxide growth and
consequently a thinner chromium oxide scale. However, as the
silicon oxide scale was not protective. Mo-oxides formed in
the bulk – Mo being an alloying element of alloy 603 –
followed by breakaway oxidation. In case of the aluminium
alloyed material the formation of nitrides in the bulk
indicated the breakdown of the oxide scale. Failure of the
alloys was related to massive inward nitrogen diffusion and
the formation of aluminium nitrides in the bulk. Therefore
it is assumed that in nitrogen rich atmospheres a high
aluminium content is unfavourable due to the strong affinity
of aluminium to nitrogen. In general it was observed, that
at lower temperatures, as a result of a slower growth
kinetic, the nitride formation began later.Short term tests
of 50 hours of alloy 602, alloy 603 and alloy 693 showed,
that a thicker and more uniform oxide layer formed when the
burner was operated with standard quality IGO (1700 mg/kg
S), compared with the oxide scale formed in the case of
operation with fuel with reduced sulphur content (20 mg/kg
S). Ventilation with air after burner shut down had no
significant effect on chromium oxide scale thickness.The
time dependence of the observed growth of the chromium oxide
scale was fitted with a power law. A deviation from the
parabolic law has been found indicating an oxide loss due to
spallation.Reasonable estimation of life time was achieved
by logarithmic plots of the time dependence of the chromium
depletion measured by line scans on cross sections of the
samples.The metallographic investigation of the hot surface
of the radiant burner showed a thin continuous chromium
oxide layer. No indication of damage of the scale, a small
depth of internal oxidation and the absence of a significant
chromium depletion zone were found. Hence, a long life time
of the woven wire cloth can be expected.},
cin = {500000},
ddc = {620},
cid = {$I:(DE-82)500000_20140620$},
typ = {PUB:(DE-HGF)11},
urn = {urn:nbn:de:hbz:82-opus-14156},
url = {https://publications.rwth-aachen.de/record/60785},
}
guest ::