ICMCTF 2012! - CD-Lab Application Oriented Coating Development

4:30pm B7-2-9 Improving thermal stability of hard coating films via a
concept of multicomponent alloying., H. Lind (halin@ifm.liu.se), R.
Forsén, B. Alling, N. Ghafoor, F. Tasnádi, M. Johansson, I. Abrikosov, M.
Odén, Linköping University, Sweden
We propose a design route for the next generation of nitride alloys via a
concept of multicomponent alloying based on self-organization on the
nanoscale via a formation of metastable intermediate products during the
spinodal decomposition. We predict theoretically and demonstrate
experimentally that quasi-ternary (TiCrAl)N alloys decompose spinodally
into (TiCr)N and (CrAl)N-rich nanometer sized regions. The spinodal
decomposition results in age hardening, while the presence of Cr within the
AlN phase delays the formation of a detrimental wurtzite phase leading to a
substantial improvement of thermal stability compared to the quasi-binary
(TiAl)N or (CrAl)N alloys.
4:50pm B7-2-10 Packing structure and optical properties of
functionalized pentacene, U. Schwingenschlogl
(udo.schwingenschlogl@kaust.edu.sa), N. Singh, Y. Saeed, KAUST, Saudi
Arabia
By their enormous variability and potential low-cost fabrication, organic
electronics attract significant commercial and scientific interest in recent
years. In particular, pentacene was studied quite extensively as organic
molecular semiconductor in various thin film applications. Although
pentacene is currently among the organic materials with the highest charge
carrier mobility, it is believed that there is still much room for improvement
if the p-p interaction can be enhanced. To this aim, functional substitution
can induce modified packing structures and electronic properties. For
example, pristine pentacene shows a slipped 1D packing, while (6,13)bis(triisopropyl-silylethynyl)-pentacene
(TIPS pentacene) realizes a
brickwork 2D packing. By introducing a trifluoromethyl group on the TIPS
pentacene backbone (TIPS-CF3 pentacene), the system becomes soluble in
common organic solvents. Moreover, the bulky side groups interrupt the
herringbone pattern and induce a regular columnar stacking of the acene
planes.
We study the effect of functional substitution and of the induced packing on
the electronic and optical properties of pentacene, TIPS pentacene and
TIPS-CF3 pentacene in comparison to each other in order to evaluate the
influence of the functional group. The results are also compared to
experimental data. Our calculations are based on density functional theory,
using the full potential linearized augmented plane wave method. Exchange
and correlation effects are treated within the local density approximation.
An enhanced difference between the band gaps of the molecule and the
crystal is found for TIPS pentacene. The frequency dependent dielectric
functions and absorption spectra are calculated and analyzed in terms of the
transitions between the highest occupied (HOMO) and lowest unoccupied
(LUMO) molecular orbitals. It turns out that C and Si states from atoms in
the chain which connects the side group to the pentacene account for the
main contribution to the optical transitions. The calculated dielectric
functions agree well with experimental data. Moreover, the experimentally
observed red shift from the molecule to the crystal is confirmed.
Tribology & Mechanical Behavior of Coatings and
Engineered Surfaces
Room: Pacific Salon 1-2 - Session E3-2/G2-2
Development, Characterization, and Tribology of
Coatings for Automotive and Aerospace Applications
Moderator: R. Evans, Timken Company, US, H. Rudigier,
OC Oerlikon Balzers AG, Liechtenstein, S. Dixit, Plasma
Technology Inc., US
1:50pm E3-2/G2-2-1 In situ tribology of cold spray-deposited pure
aluminum and Al-Al2O3 composite coatings, J.M. Shockley, R. Chromik
(richard.chromik@mcgill.ca), H. Strauss, McGill University, Canada, E.
Irissou, J.-G. Legoux, National Research Council, Canada
Cold sprayed aluminum coatings are valued for their good corrosion
resistance, but their poor tribological performance limits their use in
automotive and aerospace applications where wear resistance is also
required. Hard phases such as Al2O3 may be co-sprayed along with
aluminum powders to create Al-Al2O3 composite coatings with improved
tribological performance. Traditional ball-on-flat tribometry prevents direct
observation of the sliding interface during wear, meaning only ex situ
analysis of wear surfaces and debris is possible. In the present study, an in
situ tribometer with a transparent sapphire counterface was used for ball-onflat
testing of cold sprayed aluminum coatings deposited with up to 20
Tuesday Afternoon, April 24, 2012 44
vol.% Al2O3 particles. Similar to the use of in situ tribometry for solid
lubricants, the technique revealed details of metallic transfer film formation
and detachment. It was found that in the Al-Al2O3 cold spray coatings, the
transfer film was more stable as hard phase content increased, which was
also correlated to increase in friction stability and decreased wear.
2:10pm E3-2/G2-2-2 Thermal Spray Lubricious Oxide Coatings, S.
Dixit (sdixit@ptise.com), Plasma Technology Inc., US, O.L. Eryilmaz, A.
Erdemir, Argonne National Laboratory, US
During the extreme conditions experienced in automotives and aerospace
applications, oil-based lubricants break down at high temperatures. Under
such conditions, conventional fluid lubricants either fail early or never are
considered as an option. As a result, components of engines that are run at
high temperatures to improve their fuel efficiency tend to wear rapidly and
require replacement. One solution to extend bearing life is with the
implementation of a low friction, high temperature stable, and low wear
coatings to the component surface that can perform under extreme
conditions. Solid lubricant coatings offer a solution for diverse applications
exhibiting extreme and difficult running conditions. Although the most
common dry-solid lubricants are graphite, MoS2, WS2, TaS2, and PTFE,
they are limited in terms of their high temperature capabilities as well as
their wear characteristics. Hence in this paper we propose novel thermal
spray lubricious oxide coatings based on a crystal chemical approach.
Different combinations of the oxide materials are chosen based on their
ionic potential differences and plasma sprayed to a thickness of 150 to 200
microns. Their composition, microstructure and high temperature wear
characteristics are reported in this paper.
2:30pm E3-2/G2-2-3 Tribological properties of plasma sprayed AlSi
coatings reinforced by nano-diamond particles, M.D. Bao, Ningbo
University of Technology, China, C. Zhang, D. Lahiri, A. Argarwal
(agarwala@fiu.edu), Florida International University, US
Al-Si coatings reinforced with nano-diamond particles with different
volume percentage were prepared by plasma spraying. The composite
coatings show a two-phase microstructure of Al-Si matrix with
homogeneously dispersed nano-diamond particles. The hardness and elastic
modulus of Al-Si coatings reinforced by nano-diamond particles of various
concentrations were investigated in comparison with pure Al-Si coatings.
The tribological behavior including friction coefficient and specific wear
rate of these different coatings were also studied. The mechanism of wear
resistance and anti-friction behavior of coatings is discussed in this study.
2:50pm E3-2/G2-2-4 High temperature abrasive systems, J. Davenport
(jrd49@cam.ac.uk), R. Stearn, University of Cambridge, UK, M. Hancock,
Rolls Royce, US, W. Clegg, University of Cambridge, UK
Increasing the efficiency of a gas turbine engine requires that any leakage of
gas from the working gas path is minimized, of particular importance is
leakage around the tips of high pressure (HP) turbine blades. This can be
approached by using an abradable sealing system, where abrasive particles
embedded in an anchor phase are fixed to the end of the turbine blade tip,
and an abradable coating. The turbine blades cut a track through the
abradable coating on the shroud, the abrasive particles protect the turbine
blade from wearing away against the abradable.
However lifetimes of the current sealing system are unacceptably short,
with oxidation of the abrasive and creep of the anchor phase being two
major factors.
The abrasion behavior of various abrasives against a magnesium aluminate
spinel abradable has been studied using a pin-on-disc abrasion rig at
temperatures up to 1300 o C. It has been shown, even at the velocities of just
a few metres per second, that abrasion causes fracture of the particles and
frictional heating approximately consistent with predictions in the literature.
At elevated temperatures and at these velocities it is shown that correcting
for the difference in velocity predicts temperature changes about the melting
point of the MCrAlY, and even close to that of the abrasive.
3:10pm E3-2/G2-2-5 Customized Surface Technology for Innovative
Automotive and Industrial Products, T. Hosenfeldt
(Tim.Hosenfeldt@schaeffler.com), Y. Musayev, Schaeffler Technologies
GmbH & Co. KG, Germany INVITED
Modern components and systems for automotive and industrial applications
have to meet various requirements in multiple technical fields. Apart from
properties that affect the part itself – like geometry, stiffness, weight or
rigidity – the surface properties must be adjusted to the growing
environmental requirements. This includes measures for corrosion and wear
protection, for optimum electrical or thermal conductivity and for optical
purposes. Beyond those, coatings are increasingly used to reduce the
friction losses of car components, improve fuel efficiency and reduce CO2emissions.