ICMCTF 2012! - CD-Lab Application Oriented Coating Development

Coatings for Use at High Temperature
Room: Golden Ballroom - Session AP
Symposium A Poster Session
Thursday Afternoon Poster Sessions
AP-1 Contact Corrosion propriety between Carbon Fiber Reinforced
Composite Materials and Typical Metal alloys in an aggressive
environment, Z.J. Peng, University of Windsor, Canada, Z.J. Wang,
Univeristy of Windsor, Canada, X. Nie (xnie@uwindsor.ca), University of
Windsor, Canada
The demand for the use of carbon-fiber-reinforced materials in automotive
and aerospace industry is increasing worldwide. However, a destructive
galvanic corrosion is inevitable in the case that carbon fiber contacts with
metals. In this research, the galvanic corrosion between carbon fiber and
three kinds of commonly used metals, AISI 304 steel, A356 aluminum alloy
and Ti6Al4V titanium alloy, were studied. By employing the
potentiodynamic polarization corrosion tests and zero resistance Ammeter
tests (ZRA), the corrosion potentials and their differences in values were
determined. The corrosion behavior of the samples was evaluated in a 3.5%
NaCl solution. It was found that all the metals were corroded when they
contacted with the carbon fiber. To address the problems, plasma
electrolytic oxidation (PEO) technique were employed to synthesize oxide
coatings on the stainless steel and aluminum and titanium alloys. The
results of the experiments showed that the gavalnic corrosion rates could be
decreased significantly when the PEO coatings were applied on the metallic
surfaces. All the coatings possessed a much better corrosion resistance
compared to the uncoated substrates. Key words: Galvanic Corrosion,
Carbon Fiber, PEO Coating, Corrosion resistance Corresponding author. Email:
xnie@uwindsor.ca
AP-2 Influence of native oxide scales on the mechanical properties of
polycrystalline nickel substrates, M. Tatat (matthieu.tatat@ensma.fr), P.
Gadaud, C. Coupeau, X. Milhet, Institut P’, CNRS – ENSMA - Université
de Poitiers – UPR 3346, France, P. Renault, Institut P' - Universite de
Poitiers, France, J. Balmain, Laboratoire d’Etude des Matériaux en Milieux
Agressifs - Université de La Rochelle, France
Severe operating conditions promoting corrosion or oxidation may result to
the damage and further ruin of the considered materials. Structural materials
that are used in such aggressive environments are consequently usually
protected by passive thin films or coatings. In the case of native thermallygrown
oxides, only few studies are available in the literature concerning the
coupling effect between their ageing and the mechanical behaviour of their
associated substrate.
In this context, the influence of thermally-grown oxide films on the
mechanical properties of polycrystalline nickel substrates has been
investigated using a dynamical resonant method and instrumented
indentation tests. Being a major component of superalloys used in the
hottest parts of turbojets, nickel appears as a model material for oxidation
due to the growth of only one form of oxide (NiO). Oxide scales have been
developed at various temperatures and times to study the effect of
thicknesses and microstructures on the mechanical behavior.
The dependence of the nickel elastic constants on temperature below the
Curie temperature (631 K) is characterized by an anomalous behavior,
resulting from its ferromagnetic character. On one hand, it is shown that the
NiO layer that represents less than 3% of the total thickness of the
specimens affects however significantly the elastic constants of the oxidized
material below the Curie temperature, compared to those measured for the
substrate in the same temperature range. These experimental results suggest
that the internal stresses developed during oxidation play a key role in the
competition between the magnetostrictive and elastic expansions. On the
other hand, it is believed that these unexplored magnetoelastic coupling of
the nickel substrate explains the scattering of the elastic modulus
measurements of NiO reported in the literature.
AP-3 Evaluation of galvanic and corrosion behaviour of some
commercial aluminium-based coatings deposited by various methods,
O. Fasuba, A. Yerokhin, A. Matthews, A. Leyland
(a.leyland@sheffield.ac.uk), University of Sheffield, UK
The galvanic and corrosion behaviour of commercial slurry-coated Al-Cr-
Mg-P composite, electrodeposited Al, HVOF-Al and IVD-Al coatings was
studied in 3.5 wt. % NaCl electrolyte. The coatings were evaluated by: open
circuit potential (OCP), potentiodynamic polarisation, electrochemical noise
and electrochemical impedance spectroscopy (EIS) techniques. SEM, EDX,
XRD and optical microscopy were used to characterise the coating
structure. A comparison of the OCP vs. saturated calomel electrode (SCE)
Thursday Afternoon Poster Sessions 94
measurements in 3.5 wt. % NaCl showed that all coatings behave anodically
with respect to the steel substrate. During electrochemical noise
measurements the galvanic current density and mixed potential of the
coatings/bare mild steel couples were measured simultaneously during 12
hours of immersion. In the slurry-coated Al-Cr-Mg-P composite/bare steel
and IVD-Al/bare steel couples, bare steel was found to be anodic to the two
coatings during the initial stages of the measurement, before a polarity
reversal occurred. HVOF-Al and electrodeposited Al coatings showed
unstable potential behaviour with a fluctuating variation in current density
with increased exposure time. Overall, results of the OCP, polarisation and
the electrochemical noise measurements showed that the coatings behaved
as the anodic element of the galvanic pairing, with the slurry-coated Al-Cr-
Mg-P composite exhibiting the lowest galvanic current density which is a
desirable feature for long-term cathodic protection of the steel substrate.
The EIS analysis and the results of the structural characterisation of the
coatings correlate with that of the OCP, polarisation and electrochemical
noise measurements.
AP-4 High Temperature Diffusion Barriers for InSb based IR
Detector, A. Le Priol (arnaud.le.priol@univ-poitiers.fr), E. Le Bourhis, P.
Renault, Institut P' - Universite de Poitiers, France, H. Sik, P. Muller,
SAGEM Défense Sécurité, France
InSb based infra-red (IR) detectors are constituted by an Si supported
Integrated Circuit (IC) and an InSb matrix which are electrically and
mechanically connected thanks to solder balls in pure indium deposited on
underbump metallic layers (UBM). This UBM ensures adherence between
solder balls on both Si and InSb substrates, acts as diffusion barrier and
facilitated the wetting of solder metal. High temperature diffusion occurs
during the assembly process with intermetallic compounds (IMC) being
formed. This process may short-circuit pixels and hence dramatically
affecting the strength of the solder joint at the bonding interface.
To avoid indium diffusion across UBM, different routes have been
investigated: (i) variation of residual stresses in W-Ti thin film barrier, and
(ii) use of new refractory metal like tantalum and its nitride.
It is well known that refractory metal film deposited under the condition of
limited atomic mobility have columnar microstructure. It is unfavorable
since indium diffusion occurs along the grain boundaries. Thus, tailoring
the columns microstructure from dense under compression stress state to
porous under tension stress state has been explored since this should
improve the performance of the barrier. We indeed report on the beneficial
influence of the working pressure employed during physical deposition
(PVD) on barrier performance.
On the other hand, to develop a Ta-based barrier, it is mandatory to obtain
the stable phase of Ta (bcc α-Ta), for which deposition conditions have
been be optimized. Bi-layer TaN / Ta are shown to be a potential diffusion
barrier system. TaN underlayer is shown to promote α-Ta growth and
improve barrier performance.
AP-5 Improvement on the mechanical and corrosion properties of
nanometric HfN/VN superlattices, P. Prieto, Excellence Center for Novel
Materials, CENM, Colombia, C. Escobar, J Caicedo
(jcaicedoangulo@gmail.com), Thin Film Group, Universidad del Valle,
Colombia, W. Aperador, Ingeniería Mecatrónica, Universidad Militar
Nueva Granada, Colombia, J. Esteve, Universitat de Barcelona, Spain, M.
Gómez, Thin Film Group, Universidad del Valle, Colombia
The aim of this work is the improvement of the mechanical and
electrochemical behavior of 4140 steel substrate using HfN/VN
multilayered system as a protective coating. We have grown HfN/VN
multilayered via reactive r.f. magnetron sputtering technique in which was
varied systematically the bilayer period (Λ), and the bilayer number (n),
maintaining constant the total thickness of the coatings (~1.2 μm). The
coatings were characterized by X-ray diffraction (XRD), X-ray photo
electron spectroscopy (XPS), electron microscopy assisted with selected
area electron diffraction. The mechanical properties were analyzed by
nanoindentation method. The electrochemical properties were studied by
Electrochemical Impedance Spectroscopy and Tafel curves. XRD results
showed a preferential growth in the face-centered cubic (111) crystal
structure for [HfN/VN]n multilayered coatings. The best improvement of
the mechanical behavior was obtained when the bilayer period (Λ) was 15
nm (n = 80), yielding the highest hardness (37 GPa) and elastic modulus
(351 GPa). The values for the hardness and elastic modulus are 1.48 and
1.32 times greater than the coating with n = 1, respectively. The
enhancement effects in multilayer coatings could be attributed to different
mechanisms for layer formation with nanometric thickness due to the Hall-
Petch effect. The maximum corrosion resistance was obtained for coating
with (Λ) equal to 15 nm, corresponding to n = 80 bilayered. The