ICMCTF 2012! - CD-Lab Application Oriented Coating Development

This shift is already known in literature, but has not yet been entirely
clarified. In pursuing annealing experiments a minor effect of residual stress
on this shift was observed. Film adhesion was evaluated by a modified
scratch test. Film growth, surface topography and failure mechanisms where
analyzed by SEM imaging.
Additionally this paper gives advice to select and apply methods suitable for
deposition processes from a broad range of methods in the statistical design
of experiments (DoE).
3:30pm E3-1/G2-1-8 Numerical analysis of the influence of film
thickness and properties on the stress state of thin film-coated piston
rings under contact loads., L.G.D.B.S. Lima (luiz.lima@esss.com.br),
L.C.S. Nunes, Universidade Federal Fluminense, Brazil, R.M. Souza, N.K.
Fukumasu, Universidade de São Paulo, Brazil, A. Ferrarese, Mahle Metal
Leve S/A, Brazil
In this work, a series of finite element analyses were conducted to analyze
the stresses in thin film-coated piston rings under contact loads. The actual
normal and tangential pressure observed during a complete four-stroke
gasoline engine cycle (720 o ) was used as input to load an axisymmetric
film/substrate mesh. Four values of coating thickness were analyzed (from
20 to 100 μm) and, for each one, five values of Young´s modulus (from 144
to 578 Gpa) were considered. The systems were compared based on the
stress distribution, particularly in terms of the intensity and position of the
peak stresses in the film and at the film/substrate interface. Results show
that the stiffer (or thicker) the film, the higher the stresses at the interface
immediately under the film-sleeve contact, and the higher the compressive
stresses around this region. The range of thickness and Young’s modulus
values considered in this work did not provide significant changes in terms
of substrate stresses.
3:50pm E3-1/G2-1-9 Numerical analysis of wear and failure zones of
coated piston skirt and piston rings under scuffing conditions, N.K.
Fukumasu (newton.fukumasu@gmail.com), University of São Paulo,
Brazil, L.G.D.B.S. Lima, Universidade Federal Fluminense, Brazil, A.
Ferrarese, Mahle Metal Leve S/A, Brazil, R.M. Souza, University of São
Paulo, Brazil
In this work, 3D finite element analyses (FEA) were conducted to improve
the understanding of wear and failure of coated piston skirt and piston rings
under scuffing in fire operating conditions. The model was based on a fourstroke
port fuel engine and considered the interaction between the piston,
piston rings and the cylinder liner. Piston pin, connecting rod, crankshaft
and cylinder wall were modeled as rigid components, allowing the
reproduction of the piston dynamics. The influence of the lubricant was
considered in the simulations through a time dependent friction coefficient
at the contact points. Full combustion cycles (720 degree rotation of the
crankshaft) were simulated for velocities between 2000 and 6000rpm.
Coatings were considered in piston rings and piston skirt regions in contact
with the cylinder liner. The mechanical properties were derived from either
carbon-based or nitride-based thin films. Stress results on film surfaces and
film/substrate interfaces were analyzed to identify regions more prone to
wear due to adhesive/cohesive failure of the films. The numerical prediction
presented good correlation with literature results in terms of failure regions
and the wear zones in engine components.
4:10pm E3-1/G2-1-10 Effect of chromium on the wear mechanisms of
self-adaptive WSC-Cr sputtered coatings, T. Polcar
(t.polcar@soton.ac.uk), University of Southampton, UK, F. Gustavsson,
Uppsala University, Angstrom Laboratory, Sweden, M. Danek, Czech
Technical University in Prague, Czech Republic, A. Cavaleiro, University
of Coimbra, Portugal
Transition metal dichalcogenides (TMD) belong to one of the most
developed class of materials for solid lubrication. However, one of the main
drawbacks of most of the self-lubricating coatings is their low load-bearing
capacity, particularly in terrestrial atmospheres. In previous works, alloying
TMD thin films based on tungsten disulfide with non-metallic interstitial
elements, such as carbon or nitrogen, has been studied in order to improve
tribological performance in different environments. Excellent results were
reached having the deposited coatings hardness, in some cases, more than
one order of magnitude higher than single W-S films.
In this work, W-S-C films were alloyed with Cr by-co sputtering chromium
and composite WS2-C targets. Cr-contents in the range [0-25 at.%] were
selected for sliding tests (pin-on-disc, 100Cr6 steel ball as a counterpart)
under different conditions (dry or humid air, increasing load, etc.) Besides
the usual physical, chemical and mechanical characterization, including the
evaluation of the chemical composition, the structure, the morphology, the
hardness and the cohesion/adhesion, special attention was paid to the
friction and wear analyses. The surfaces in the contact were analysed by Xray
photoelectron spectroscopy (bonding), Auger emission spectroscopy
(surface chemical composition), and scanning electron microscopy (SEM).
Monday Afternoon, April 23, 2012 18
Selected ball wear scars and wear tracks were investigated by transmission
electron microscopy (TEM); the samples for them were prepared by focus
ion beam (FIB).
Surface and sub-surface structural modification of the coating and
composition of the transferred tribolayer are discussed in detail. The main
aim of this study is to shed light on following issues: i) the role of Cr in
microstructural transformation, ii) the role of Cr in sliding process, iii) the
formation of low-friction tribolayer based on tungsten disulfide.
4:30pm E3-1/G2-1-11 Performance impact of honing dynamics on
surface finish of precoated cylinder bores, M. El Mansori
(mohamed.elmansori@ensam.eu), Arts et Métiers ParisTech, France, B.
Goeldel, L. Sabri, Renault sas, France
Minimization of the friction losses is a major concern for Internal
Combustion Engine designers. The strategy often followed, to reduce
losses, is to modify the topography of the rubbing surfaces of the cylinder
bores and the piston rings. This strategy aims to reduce metallic friction and
to allow less oil consumption and high operational reliability. The surface
modification of cylinder bore with improved sliding properties is often
produced at industrial level by honing process. Abrasive stones are hence
loaded against the bore and simultaneously rotated and oscillated. To
guarantee a robust surface production of cylinder bore of specific shape
with acceptable dimensional accuracy and surface quality, the stone
dynamic effects in continuous balanced contact with the workpiece are of
primary importance. This paper addresses these effects on honed surface
structure of cylinder bores. The stone dynamic behavior while bore honing
was studied at conventional regime ranged from 0,5g to 1,5g as often used
in mass bore production. Under these dynamic conditions of bore
processing, the dimensional accuracy holds by opposition to the surface
appearance. However, the highly accelerated regime in honing up to 2,5g
promotes simultaneously the form quality (especially straightness) and
reduces the cycle time. The reported results are the first demonstration that
the bore surface finish can be dynamically controlled when honing. This
technology is enabled by a microscale regeneration mechanism of abrasive
stones.
4:50pm E3-1/G2-1-12 Macroscopic simulation of the liner honing
process, B. Goeldel (benoit.goeldel@gmail.com), Renault SAS, France, M.
El Mansori, Arts et Métiers ParisTech, France, L. Sabri, Renault SAS,
France
The honing process produces surface liners with specific functional
properties. Engine performances and life expectancy are directly impacted
by the quality of honed surface. The form quality, the roughness and the
surface appearance produce by honing determine the friction of the piston in
the liner. The process is however mechanically complex and the selection of
the process parameters is currently based on empirical methods. The aim of
this paper is thus to develop a macroscopic simulation environment which
will help end-users during this setting-up stage. The development of this
virtual tool is based on a space-time discretization and a macroscopic
cutting model taking into account local contacts between the workpiece and
the abrasives tool. The space-time discretization allows representing the
machine environment with the tool, the workpiece and the machine
kinematic. The cutting model allows converting kinematics and abrasive
contacts in dynamic data and material removal rate by calculation. Initially
the cutting model was adjusted on simple experiments. After, we have
extrapolated the stock removal equation to the whole range of stone cutting
condition. This approximation allows simulating the real process. The
simulation of a whole honing cycle is possible and results were validated by
comparison with industrial context experiments. The simulation of the
whole honing cycle allow to predict the form quality, one of the roughness
criteria and the surface appearance. Simulation results are represented in
mapping which allow seeing quality criteria for each point of the surface.
5:10pm E3-1/G2-1-13 Fiction and adhesion of Si and F incorporating
diamond-like carbon (DLC) coatings sliding against aluminum, F.G.
Sen (senf@uwindsor.ca), X. Meng-Burany, University of Windsor, Canada,
M.J. Lukitsch, Y. Qi, General Motors Research and Development Center,
US, A.T. Alpas, University of Windsor, Canada
Diamond-like carbon (DLC) coatings exhibit low coefficient of friction
(COF) and good adhesion mitigating properties when placed in sliding
contact against aluminum but their tribological properties are very sensitive
to the environmental conditions. This study examines tribological properties
of 20 at % Si and 12 at % F containing DLC coatings (with 14 at % O and
18 at % H) tested against 1100 aluminum under a vacuum atmosphere (0.01
Pa) and an ambient air (39% relative humidity) condition. Pin-on-disk type
sliding test showed a COF of 0.08 under both conditions. The changes in
contact surface tribo-chemistry and material transfer processes were
studied. Carbonaceous transfer layers that incorporated F, Si and O
compounds formed on aluminum contact surface under both testing