ICMCTF 2012! - CD-Lab Application Oriented Coating Development

3 [http://www.mrl.uiuc.edu/], [http://www.uiuc.edu/],104 S. Goodwin
Avenue, [http://www.city.urbana.il.us/Urbana/], IL 61801, USA
A unique self-organized nanostructure is reported for (Zr0.64Al0.36)N thin
films that forms during reactive magnetron sputter deposition from
elemental targets on MgO(001) substrates. HRTEM and EDX/STEM
imaging shows that it consists of a nanolabyrinth of alternating ZrN-rich
and AlN-rich lamellae along the MgO in plane directions, with
typical width of a 4 nm and that extends throughout the film thickness.
According to ab-initio calculations, a significantly higher solid solution
mixing enthalpy of c-Zr0.6Al0.4N (∆H=0.392 eV/f.u), compared to c-
Ti0.6Al0.4N (∆H 0.178 eV/f.u) results in a comparatively higher driving force
for isostructural decomposition in ZrAlN during secondary phase
transformation on post annealing. Growth kinetics and pseudomorphic
epitaxial forces also effects the segregation to occur during growth.
The phase segregation is studied in 1.5 µm thick (Zr0.64Al0.36)N films grown
at different temperatures between 500-900 °C. It is shown that a maximum
hardness of ~38 GPa is associated with a nano-labyrinthine nanostructure
that forms at higher temperatures. The ZrN/AlN phase separation is
complete at 900°C. The ZrN rich platelets retain the original B1 NaCl
structure with cube on cube epitaxy with the MgO substrate, whereas the
AlN-rich regions transform to wurtzite. The geometrical arrangement and
the mutual relationships of the two phases on decomposition will be
presented with respect to the growth temperatur
9:00am B5-1-4 Wear/erosion behavior of TiN-based nanocomposite
coatings on SS304 and a synchrotron radiation assisted coating failure
investigation, Y. Li (yul088@mail.usask.ca), Q. Yang, A. Hirose,
University of Saskatchewan, Canada, R. Wei, Southwest Research Institute,
US
Thick TiN and a series of TiN-based nanocomposite coatings have been
deposited on SS304 substrates using a plasma enhanced magnetron
sputtering technique. The morphology, microstructures were characterized
by SEM, AFM and XRD. The mechanical properties are measured by
indentation testings (Rc, micro- and nanoindentations). The tribological
performances were evaluated by solid particle erosion testing and pin-ondisk
wear testing. The results reveal that the hard coatings imposed have
significantly improved the tribological properties of the bare steel
substrates. A preliminary synchrotron radiation-based analysis was further
performed to track the microstructure and composition changes and stress
state distribution in the damaged coatings after tribological testing. The
coating failure mechanism was discussed.
9:20am B5-1-5 Erosion Mechanisms of Hard Nanocomposite Coatings,
E. Bousser (etienne.bousser@polymtl.ca), L. Martinu, J.E. Klemberg-
Sapieha, École Polytechnique de Montréal, Canada INVITED
Economic and technological progress as well as environmental concerns
requires that modern equipment be designed with ever more stringent
performance criteria, frequently pushing components to the very limits of
their capabilities. Consequently, tribological deficiencies, such as
lubrication breakdown, excessive wear and tribo-corrosion, are amplified
leading to unnecessary operational costs, decreased efficiency and
premature failure. Therefore, appropriate material’s selection for a given
application must be guided by an accurate understanding of the intervening
tribological processes.
Solid Particle Erosion (SPE) occurs in situations where hard solid particles
present in the environment are entrained in a fluid stream, and impact
component surfaces. It is well known that ductile materials erode
predominantly by plastic cutting or ploughing of the surface, while brittle
materials do so by dissipating the particle kinetic energy through crack
nucleation and propagation. Although the most widely accepted brittle
erosion models were developed more than 30 years ago, little has been
published on how the material removal process differs for hard brittle
coatings when compared to bulk materials. In this presentation, we outline
the work performed at École Polytechnique on understanding the material
loss mechanisms occurring during the SPE of hard coatings.
In the first part, we will discuss the validity of existing brittle SPE models
when applied to the erosion of hard coatings. We examine the mechanisms
by which surfaces dissipate the kinetic energy of impacting particles, and
compare the erosive response of brittle bulk materials to that of hard
coatings. Also, we investigate the means by which surface engineering can
enhance erosion resistance, and correlate surface mechanical properties to
the erosion behaviour of brittle bulk materials and coatings. We will show
that the experimental results are also well supported by the finite element
modelling of single particle impacts of coated surfaces.
The second part of the talk will focus more closely on TiN-based hard
nanocomposite coatings and on the role microstructure has on the surface
mechanical properties and on the enhanced erosion performance. Finally,
erosion tests being notoriously inaccurate, we discuss the methodology of
Wednesday Morning, April 25, 2012 54
coating erosion testing, and present a novel in-situ erosion characterization
technique used for time-resolved erosion testing.
10:00am B5-1-7 Effects of structure and phase transformation on
fracture toughness and mechanical properties of CrN/AlN multilayers,
M. Schlögl (manfred.schloegl@unileoben.ac.at), J. Paulitsch, J. Keckes, C.
Kirchlechner, P.H. Mayrhofer, Montanuniversität Leoben, Austria
Transition metal nitrides, such as CrN are highly attractive materials for a
wide range of applications due to their outstanding properties like high
hardness, excellent corrosion and oxidation resistance. Consequently, many
research activities deal with their synthesis-structure-properties-relations.
However, also because the fracture toughness of thin films is a difficult-toobtain
material property, only limited information is available on this topic.
Therefore, this work is devoted to the study of the fracture mechanisms of
CrN based thin films with the aid of in-situ scanning electron microscopy
microbending, microcompression and microtension tests. The small testspecimens
are prepared by focused ion beam milling of individual freestanding
thin films. As generally monolithic coatings with their columnar
structure provide low resistance against crack formation and propagation we
perform our studies for CrN thin films and CrN/AlN multilayers. The latter
offer additional interfaces perpendicular to the major crack-propagationdirection
having different elastic constants and shear modulus and binding
characteristics. Adjusting the AlN layer-thicknesses to ~3 and ~10 nm
allows studying the impact of a cubic stabilized AlN layer and an AlN layer
composed of cubic, amorphous and hexagonal fractions being extremely
sensitive to stress fields.
The microtests clearly demonstrate that the monolithic CrN as well as the
CrN/AlN multilayer coating with the ~10 nm thin AlN layers (and hence a
mixture of cubic, amorphous and hexagonal AlN phases) fail as soon as
small cracks are initiated. Contrary, the CrN/AlN multilayer coatings
composed of ~3 nm thin c-AlN layers are able to provide resistance against
crack propagation. Hence, they allow for significantly higher loads during
the tests. Detailed structural investigations, in-situ and after the tests,
suggest that the cubic AlN layers, which are stabilized by coherency strains
in the CrN/AlN multilayer coatings, phase transform when experiencing
additional strain fields and thereby hinder crack propagation.
10:20am B5-1-8 Nanoindentation and fatigue properties of magnetron
sputtered AlN/NiTi multilayer thin films, D. Kaur
(dkaurfph@iitr.ernet.in), N. Choudhary, Indian Institute of Technology
Roorkee, India
The present study explored the in-situ deposition of high damping AlN/NiTi
multilayer heterostructures with different bilayer periods (Λ) and bilayer
numbers (n) by using dc/rf magnetron sputtering. The heterostructures were
characterized in terms of structural, morphological, mechanical and
damping properties by XRD, FESEM and Nanoindentation, respectively.
XRD analysis revealed the formation of highly oriented AlN and NiTi
films. The higher hardness and elastic modulus of multilayer coatings could
be attributed to different mechanisms for layer formation with nanometric
thickness and better adhesion of AlN layer with NiTi. The enhanced
damping and fatigue properties of AlN/NiTi multilayers was due to the
combined effect of piezoelectric AlN and NiTi shape memory alloy layers.
The obtained results suggest that AlN/NiTi multilayers exhibit higher
damping capacity as compared to PZT/NiTi heterostructures.
Keywords: Sputtering; Heterostructures; Nanoindentation; Damping
10:40am B5-1-9 Hardness of CrAlSiN nanocomposite coatings at
elevated temperatures, S. Liu (sl559@cam.ac.uk), S. Korte, Gordon
Laboratory, Department of Materials Science and Metallurgy, University of
Cambridge, UK, X.Z. Ding, X.T. Zeng, Singapore Institute of Manufacturing
Technology, Singapore, W. Clegg, Gordon Laboratory, Department of
Materials Science and Metallurgy, University of Cambridge, UK
Cr-based nanocomposite coatings are attracting increasing attention for use
as protective coatings in dry machining and aerospace applications where
the components are consistently exposed to high temperatures. In this
report, CrAlSiN nanocomposite coatings have been deposited with different
silicon contents and at different substrate bias voltages using a lateral
rotating cathode arc technique. Their composition, microstructure and
mechanical properties were characterized using EDS, XRD and
nanoindentation respectively and compared with CrN and CrAlN coatings
deposited under the same conditions. The flow behaviour around the indent
has been studied using AFM and TEM. The mechanical behaviour of the
coatings has been determined both from room temperature tests after
annealing at elevated temperatures and hot stage nanoindentation, allowing
the hardness to be measured at temperatures up to 600 °C. The evolution of
the structure and internal stress has been measured in both cases allowing
the two approaches to be compared.