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JTST
HIGHLIGHTS
13
The
Journal of Thermal Spray Technol-
ogy
(JTST),
the official journal of the ASM
Thermal Spray Society, publishes con-
tributions on all aspects—fundamental
and practical—of thermal spray science,
including processes, feedstock manufac-
ture, testing, and characterization. As the
primary vehicle for thermal spray informa-
tion transfer, its mission is to synergize the rapidly advancing
thermal spray industry and related industries by presenting
research and development efforts leading to advancements
in implementable engineering applications of the technology.
Articles from the October and December issues, as selected
by
JTST
Editor-in-Chief Armelle Vardelle, are highlighted here.
The December issue also features the 7th Asian Thermal Spray
Conference (ATSC-7). In addition to the print publication,
JTST
is available online through springerlink.com. For more infor-
mation, visit asminternational.org/tss.
ESTABLISHED AND ADAPTED DIAGNOSTIC
TOOLS FOR INVESTIGATION OF A SPECIAL
TWIN-WIRE ARC SPRAYING PROCESS
Johannes König, Michael Lahres, Stephan Zimmermann,
and Jochen Schein
In a twin-wire arc spray (TWAS) process developed by
Daimler AG, known as LDS (Lichtbogendrahtspritzen), gas in-
jection and arc feed play a crucial role in separating molten
particles from the wire ends. This paper describes an investi-
gation of the gas and particle behavior according to individual
LDSprocessparameters. Coatingproblemsarenot considered.
Measurements are separated into two different parts: Cold
(without arc and particles) and hot (with arc and particles).
Results provide the first detailed understanding of the effect of
different LDS process parameters. A correlation between the
gas parameter settings and the particle beam properties was
found. Using established and adapted diagnostic tools, also
used in conventional TWAS processes, this special LDS process
was investigated and the results (gas and particle behavior)
validated, thereby allowing explanation and comparison of
the diagnostic methods, which is the main focus. Based on
error analysis, individual instabilities, limits, and deviations
during the gas determinations and particlemeasurements are
explained in more detail. The paper concludes with presenta-
tion of the first particle-shadow diagnostic results and main
statements regarding these investigations (Fig. 1).
MANUFACTURING AND PROPERTIES OF
HIGH-VELOCITY OXYGEN FUEL
HVOF)-SPRAYED FeVCrC COATINGS
Paolo Sassatelli, Giovanni Bolelli, Luca Lusvarghi, Tiziano
Manfredini, and Rinaldo Rigon
This paper studies the microstructure, sliding wear be-
havior, and corrosion resistance of high-velocity oxygen fuel
(HVOF)-sprayed FeVCrC-based coatings. Various process pa-
rameters were tested to evaluate their effects on coating prop-
erties, which were also compared to those of HVOF-sprayed
NiCrBSi and Stellite-6 coatings. Fe-alloy coatings are com-
posed of flattened splats, originating from molten droplets
and consisting of a super-saturated solid solution, together
with rounded particles, coming from partially unmolten ma-
terial and containing V- and Fe-based carbide precipitates. All
process parameters, apart from extreme settings with excess
comburent in the flame, produce dense coatings, indicat-
ing that the feedstock powder is quite easily processable by
HVOF. These coatings, with a microhardness of 650-750 HV0.3,
exhibit wear rates of ≈2 × 10
−6
mm
3
/(Nm) in ball-on-disk tests
against sintered Al
2
O
3
spheres. They perform far better than
the reference coatings, and better than other Fe- and Ni-base
Fig. 1 —
Laser doppler anemometry: Principle of setup.
Fig. 2 —
SEMmicrograph of Sample 1 cross-section after electro-
chemical polarization test.