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@ARTICLE{Mauer:824696,
author = {Mauer, Georg and Sebold, Doris and Vaßen, Robert and
Hejrani, Elham and Naumenko, Dmitry and Quadakkers, Willem
J.},
title = {{I}mpact of {P}rocessing {C}onditions and {F}eedstock
{C}haracteristics on {T}hermally {S}prayed {MC}r{A}l{Y}
{B}ondcoat {P}roperties},
journal = {Surface and coatings technology},
volume = {318},
issn = {0257-8972},
address = {Amsterdam [u.a.]},
publisher = {Elsevier Science},
reportid = {FZJ-2016-07254},
pages = {114 -121},
year = {2017},
abstract = {One of the options to manufacture MCrAlY bondcoats (M = Co,
Ni) for thermal barrier coating systems is High Velocity
Oxy-Fuel spraying (HVOF). In this work, particle diagnostics
were applied to investigate the impact of processing
conditions and feedstock characteristics on the relevant
bondcoat properties. The results showed that compromises
must be made on the oxygen/fuel ratio, spray distance, and
particle size distribution to strike a balance between low
oxidation and dense microstructures.These limitations
initiated the development of the High Velocity Atmospheric
Plasma Spray process (HV-APS) as a further alternative
process. In this work, HV-APS process parameters were
developed for a three cathode torch in combination with a 5
mm diameter high speed nozzle. A one-dimensional calculation
of the expansion through this nozzle to atmospheric pressure
yielded supersonic conditions with a Mach number of 1.84.
The calculated plasma temperatures at the nozzle exit and in
the expanded jet are 8400 K and slightly above 5200 K,
respectively, which is low compared to conventional APS
processes.A very fine powder with a median particle size of
18 μm was identified to be most suitable. Although the
spray conditions were relatively cold, reasonable deposition
efficiencies up to $61\%$ and rather dense coatings were
achieved using this feedstock. The as-sprayed porosity was
≈ $2\%$ which was reduced by the subsequent vacuum heat
treatment to < $1\%.$ The oxygen content determined by
chemical analysis for a sample sprayed at a spray distance
of 100 mm was 0.41 ± 0.04 $wt\%.Moreover,$ reference
samples were manufactured by Low Pressure Plasma Spraying
(LPPS). The oxidation behavior was compared in isothermal
and cyclic oxidation tests. The oxidation rates of the
HV-APS coatings were found to be significantly lower than
those of LPPS coatings. The thermally grown oxide scale
showed less yttrium incorporation and better adherence in
case of HV-APS. The latter is suggested to be related to a
unique new distribution of Y-rich nano-sized oxide
precipitates. The cyclic oxidation test confirmed the better
oxidation resistance of the HV-APS coatings.},
cin = {IEK-1 / IEK-2},
ddc = {620},
cid = {I:(DE-Juel1)IEK-1-20101013 / I:(DE-Juel1)IEK-2-20101013},
pnm = {111 - Efficient and Flexible Power Plants (POF3-111)},
pid = {G:(DE-HGF)POF3-111},
typ = {PUB:(DE-HGF)16},
UT = {WOS:000402356100014},
doi = {10.1016/j.surfcoat.2016.08.079},
url = {https://juser.fz-juelich.de/record/824696},
}