ICMCTF 2012! - CD-Lab Application Oriented Coating Development

EP-13 Adhesion tendency of polymers to hard coatings, M. Rebelo de
Figueiredo (marisa.figueiredo@unileoben.ac.at), C. Bergmann, C. Ganser,
C. Teichert, C. Mitterer, Montanuniversität Leoben, Austria
In micro-injection moulding of small, precise and complex-shaped polymer
parts, adhesion between the mould and the polymer needs to be minimized
to achieve the requested tolerances of the parts and sufficient lifetime of the
mould. Therefore, friction and wear behavior of the coating materials TiN,
CrN, Al2O3, CrAlN, TiAlN and TiCN as well as an uncoated high-speed
steel were studied against the polymers of interest polyoxymethylene
(POM), polyamide 6.6 (PA 6.6) and polyether ether ketone (PEEK). Ballon-disk
tests in ambient air were performed at half of the melting
temperature for each polymer. For POM and PEEK, the lowest friction
(~0.15) and counterpart wear volume (7.8 x 10 -4 mm 3 ) were observed for
CrN, whereas for PA 6.6 TiCN and TiAlN showed the lowest friction
(~0.55) and CrN the lowest counterpart wear volume (1.2 x 10 -3 mm 3 ). Exsitu
Raman analyses carried out on the wear tracks of both parties revealed
that chemical changes in the contact were only observed for the high-speed
steel, giving evidence of the presence of hematite and magnetite and most
importantly transfer material of the polymer counterparts. Correlations
between the Raman results as well as roughness and surface energy to the
obtained friction and wear properties provided new insights regarding the
understanding of the tribological behavior.
EP-14 Effect of Nitrogen content on the Microstructure and Residual
Stress of Ternary Ta-Ti-N Thin Films Using Magnetron Sputtering,
C.K. Chung (ckchung@mail.ncku.edu.tw), Y.R. Lu, T.S. Chen, C.H. Li, Y.T.
Lin, National Cheng Kung University, Taiwan
Binary transition metal nitride of Ta-N and Ti-N film has been extensively
applied as diffusion barriers for Cu interconnection and hard coatings for
protective application. The combination of Ta-N and Ti-N is expected to
extend and develop functional for promising application of films. However,
the films’ buckling and peel off from substrate may be observed due to high
residual stress. In this paper, the ternary Ta-Ti-N thin films were fabricated
by magnetron co-sputtering using various nitrogen flow ratios (FN2%) of 0-
20% for studying the evolution of microstructure and residual stress of
films. The microstructure, morphology, composition, and residual stress of
Ta-Ti-N films were measured by grazing incident angle X-ray diffraction
(XRD), scanning electron microscopy (SEM), energy dispersed spectrum,
and surface profilemeter with curve fitting by Matlab, respectively. XRD
patterns showed that Ta-Ti film is body center cubic structure with three
distinct (110), (200) and (211) diffraction peaks and the phase transforms to
face center cubic (FCC) structure as over 5 FN2%. The SEM image showed
that the particle was precipitated on the film’s surface at 20 FN2% due to
the over solubility of Ta-Ti-N. The tensile stress of 2.36 GPa was observed
from the film at 0 FN2% while the compressive stress of 1.64 GPa was
obtained at 10 FN2%. The relationship between the nitrogen flow ratios,
microstructure and residual stress of ternary Ta-Ti-N thin films is discussed
and established.
EP-15 A study of microstructures and mechanical properties of
cathodic arc deposited ZrSiN coatings with silane gas, S.H. Huang,
National Chiao Tung University, Taiwan, T.C. Tseng, C.Y. Tong, Y.B. Lin,
J.W. Lee (jefflee@mail.mcut.edu.tw), Ming Chi University of Technology,
Taiwan, T.E. Hsieh, Gigastorage Corporation, Taiwan, J.G. Duh, H.W.
Chen, National Tsing Hua University, Taiwan
The ZrSiN coatings were deposited by the cathodic arc deposition system.
The silane gas flow rate was adjusted to fabricate the ZrSiN coatings with
different silicon contents. The crystalline structure of coatings was
determined by a glancing angle X-ray diffractometer. Microstructures of
thin films were examined by a scanning electron microscopy (SEM) and
transmission electron microscopy (TEM), respectively. A nanoindenter,
scratch tester and pin-on-disk wear tests were used to evaluate the hardness,
adhesion and tribological properties of thin films, respectively. It was found
that the hardness and tribological properties were strongly influenced by the
silane gas flow rate, i.e. the Si contents of the ZrSiN coatings. Optimal
silicon content for the ZrSiN coating was proposed in this work.
EP-16 Effect of micro-droplets and surface morphology on the local
residual stress field in thin hard coatings, E. Bemporad
(e.bemporad@stm.uniroma3.it), M. Sebastiani, M. Piccoli, F. Carassiti,
University of Rome "Roma Tre", Italy
The effect of surface defects on the residual stress distribution in thin
coatings has been investigated by an innovative high resolution
methodology, which mainly consists of incremental focused ion beam (FIB)
ring-core milling (IµRCM), combined with high-resolution in situ SEM-
FEG imaging of the relaxing surface and a full field strain analysis by
digital image correlation (DIC). The through-thickness profile of the
residual stress can be obtained with sub-micron spatial resolution (both
lateral and in-depth), by comparison of the experimentally measured surface
strain with finite element modeling using Schajer’s integral method.
Thursday Afternoon Poster Sessions 114
Commercial Titanium Nitride (TiN) and Chromium Nitride (CrN) coatings
were produced by Cathodic Arc Evaporation Physical Vapor Deposition
(CAE-PVD) on tool steel substrate, which were prepared at three different
roughness levels.
Preliminary characterization of coatings consisted on nanoindentation
testing, FIB cross section microstructural analysis and XRD (sin2ψ) average
residual stress measurement and micr-scratch testing on each coating.
Local residual stress were measured by the IµRCM method nearby to
droplets of different size, with the main aim of investigating the effect of
such defect on the residual stress in-depth distribution. FIB cross section
were also prepared in correspondence of each test, in order to investigate
the changes of microstructure and growth mechanism due to the defect.
Residual stress were also measured in correspondence of surface roughness
defects (polishing scratches, wrinkles, asperities). A series of stress
measurements were finally performed on the homogeneous defect-free
coating
Significant differences were found in terms of residual stress and stress
gradient in proximity of surface defects, in comparison with the residual
stress measured in defect-free areas.
In case of micro-droplets, such differences were attributed to significant
modification of growth mechanisms and microstructure of the coating. This
assumption was supported by the microstructural FIB-SEM observation,
which showed anomalous grain growth and changes in crystal orientation in
correspondence of a droplet.
Finally, the observed surface residual stress local variation where correlated
to the failure modes during scratch test, which could be affected by local
residual stress peaks.
EP-17 Tribological Behaviour of Electrodeposited CoW-WC
Nanocomposite Coatings, S.K. Ghosh (sghosh@barc.gov.in), A.K. Suri,
BARC, India, J.P. Celis, KUL, Belgium
Research for alternatives to electroplated hard chromium coatings is
continued because of their tremendous environmental and health hazard
concern. Among the various possibilities, recently, electroplated Co-W
alloys show promising results like abrasive wear and corrosion resistance
close to and even better than electroplated hard chromium. In the present
study, the Co-W alloy matrix is further strengthened by incorporating nanosize
WC particle ( 500 nm) via electrochemical codeposition technique. The
matrix cobalt helps in binding the WC particles and in return particles
strengthen the matrix along with host tungsten as alloy element. A sulphatetungstate
based electrolyte was used to electrodeposit the Co-W alloys and
Co-W-WC nanocomposites. In order to increase the particle-content within
the alloy matrix, effect of current density and particle loading within the
electrolyte were investigated in detail. Nanoindentation was used to
evaluate the nanohardness and elastic modulus of the CoW alloys and
CoW-WC nanocomposites deposited under identical current density
conditions in order to study the strengthening performances. No drastic
change in hardness was observed in case of nanocomposite as compared to
alloy counterpart. On the other hand, a significant improvement in wear
behaviour was noticed for CoW-WC nanocomposites in comparison to
CoW alloy coatings. The fretting tests were performed at a normal load of
2-10N, keeping the total displacement amplitude at 200 μm, the frequency
at 5 Hz for 10000-100000 cycles in humid air (50% RH) at 23 °C. A
corundum (Al2O3) ball of 10 mm diameter was used as counter body.
Typical wear volume measured in case of CoW-WC (deposited at
50mA.cm -2 ) under 3D optical profilometer was almost half of CoW alloy
(deposited at 50mA.cm -2 ), after fretting test under identical conditions. Post
deposition annealing of these coatings was done to found influence on
hardness and wear rate. The observed wear rate data of coatings will be
discussed in the light of microstructure, crystal structure and surface
morphology of the as deposited coating and wear scar analysis. A special
attention was given to correlate nanohardness, elastic modulus with the
measured wear rate of these coatings.
EP-18 Duplex coating of DLC films for Al and Al alloys, Y. Sakamoto
(yukihiro.sakamoto@it-chiba.ac.jp), Chiba Institute of Technology, Japan
Aluminum is one of light metals and thermal conductivity of aluminum and
its alloy is excellent. However, tribological properties of aluminum and
aluminum alloys are worse compared with iron based material.
On the other hand, “Duplex coating” is a one of hardening processing such
as thin nitride film formation on the surface of nitrided layer. The adhesion
strength was improved by introducing of the chemical bonding between the
film and the substrate using this method.
In this study, duplex coating of Diamond Like Carbon coating on the nitride
layer were studied to improve the tribological properties of aluminum and
aluminum alloys.
AC8A and ADC12 were used as the substrates. The mixture of NH3 and H2
was used as a reaction gas of radical nitriding. DLC films were prepared on