ICMCTF 2012! - CD-Lab Application Oriented Coating Development

loading situations could help to obtain somewhat more generic parameters
for tribological simulations and life-time predictions.
In a second part of the presentation and based on the results obtained for
B(P) a theoretical feasibility study will tackle the question whether or
whether not it is possible to obtain hardness values higher than 100GPa (so
called "ultra hardness") for nano-composite TiN/a-Si3N4 and nanocomposite
TiN/a-Si3N4/TiSi2 coating materials. For this an effective indenter
concept is used which also takes into account the pressure induced increase
of the Young's modulus and yield strength during indentation. It will be
shown that these hardnesses could IN PRINCIPLE be obtained.
11:00am E2-1-10 A review of claims for ultra hardness in
nanocomposite coatings, A. Fischer-Cripps
(tony.cripps@ibisonline.com.au), Fischer-Cripps Laboratories Pty Ltd,
Australia INVITED
There has been intense interest over the past 10 years concerning claims of
the production and mechanical property measurement of ultra-hard (H >
100 GPa) nano composite coatings, particularly in relation to the work of
Prof S. Veprek of the Technical University, Munich. In 2006, the present
author prepared a critical review of the methods used to characterise these
coatings for measurements of elastic modulus and hardness. At that time,
various serious errors in procedure were identified in previous works that
called into question the validity of the claimed values of elastic modulus
and hardness. It was not possible to directly verify the claimed hardness
values in excess of 100 GPa for the coatings under review. Since then,
Professor Veprek and colleagues have published numerous works which
deal with the reasons why such coatings could be made, with the
implication and statement that their earlier coatings, whose hardness has
now degraded, must have indeed been ultra-hard as claimed. In this
presentation, earlier data will be re-examined in the light of new
information about the coatings, as well as a critical review of the more
recent papers dealing with the supporting theories in relation to these
coatings. It is shown that contrary to the claims made, the expected upper
limit of hardness achievable with these types of coatings is expected to be
about 65 GPa and that the coatings themselves, made many years ago, most
likely had a hardness of between 55 and 60 GPa.
Tribology & Mechanical Behavior of Coatings and
Engineered Surfaces
Room: Pacific Salon 1-2 - Session E4-2/G4-2
Coatings for Machining Advanced Materials and for use
in Advanced Manufacturing Methods
Moderator: M. Arndt, OC Oerlikon Balzers AG,
Liechtenstein, X. Nie, University of Windsor, Canada
8:00am E4-2/G4-2-1 New Coating Systems for Temperature
Monitoring in Turning Processes, M. Kirschner (kirschner@isf.de), K.
Pantke, D. Biermann, Institute of Machining Technology, Germany, J.
Herper, W. Tillmann, Institute of Materials Engineering, Germany
High temperature loads in cutting processes can cause high tool wear and
damages in the subsurface zone of the workpiece. Especially the interaction
between the different cutting parameters affects the thermal loads in the
cutting zone. Hence, the knowledge of temperatures in cutting processes is
an important fact and is under the main focus of current investigations.
Therefore, this paper deals with an in-process monitoring system for the
resulting temperatures in a turning process. In contrast to the investigations
performed hitherto, this research deals with a new tool sensor system for
temperature measurement. This sensor system is realized by a PVD coating
of a Nickel and a Nickel-Chromium layer on the rake face of cutting inserts.
On the junction points of this layer system, three thermocouples are formed.
The development of the coating system and the resulting measurement is
shown. Additionally, the results are discussed in comparison to thermal
imaging system and conventional thermocouples.
8:20am E4-2/G4-2-2 Hybrid TiSiN, CrCx/a-C:H PVD Coatings
Applied to Cutting Tools, W. Henderer (ted.henderer@kennametal.com),
F. Xu, Kennametal Incorporated, US
A very new development in cutting tools has been made for machining
aluminum. Hybrid PVD coatings consisting of a superhard TiSiN base layer
and a low friction CrCx/a-C:H top layer are used on cutting tools where the
combination of low friction and resistance to abrasion is required. For
example when machining aluminum silicon, CrCx/ a-C:H resists the
adhesion and galling of aluminum to the cutting tool by reducing friction
and TiSiN strongly resists abrasive wear.
Coatings deposited by sputtering Cr targets in an Ar + CH4 glow discharge
have been previously studied. A nanocomposite microstructure was formed
containing CrCx crystallites in a Cr containing amorphous diamond-like
C:H matrix [1].
In this research, TiSiN films with a CrCx/C top layer have been produced in
a hybrid cathodic arc/sputter physical vapor deposition system. Applied by
cathodic arc plasma deposition, X-ray diffraction shows TiN changes from
a (111) preferred orientation to (200) texture structure with silicon
additions. When CrCx/C is subsequently deposited by sputtering, CrC XRD
peaks are not found. The material is amorphous. SEM and TEM reveal the
complex microstructure of the hybrid coating.
Measured by nano-indentation hardness tests, Si is shown to increase the
hardness of TiSiN. When machining abrasive 390 aluminum, the wear
resistance of taps coated with TiSiN base layer and a low friction CrCx/C
top layer is likewise improved with silicon additions to TiN. The CrCx/C
top layer is shown to have frictional and wear characteristics similar to DLC
coatings.
[1] Gassner, G., et al., “Structure of Sputtered Nanocomposite CrCx/a-C:H
Thin Films”, J. Vac. Soc. Technol. B, Vol. 24, No. 4, July/Aug 2006
8:40am E4-2/G4-2-3 Effect of the Cutting Edge Entry Impact Duration
on the Coated Tool’s Wear in Down and Up Milling, K.-D. Bouzakis
(bouzakis@eng.auth.gr), Aristoteles University of Thessaloniki; Fraunhofer
Project Center Coating in Manufacturing, Greece, G. Katirtzoglou, E.
Bouzakis, S. Makrimallakis, G. Maliaris, Aristoteles University of
Thessaloniki; Fraunhofer Project Center Coatings in Manufacturing, Greece
The knowledge of tool wear mechanisms in milling is pivotal for explaining
the coating failure and adjusting appropriately the cutting conditions. In the
described investigations, coated cemented carbide inserts were applied in up
and down milling hardened and stainless steel for monitoring the tool wear
at various repetitive cutting loads and durations. The variable stress, strain
and strain rate fields developed in the tool during cutting affect the filmsubstrate
deformations and in this way the resulting coating loads and
fatigue failure.
For investigating the influence of cyclic impact loads magnitude and
duration on the film fatigue failure of coated specimens, an impact tester
was employed which facilitates its force signal modulation. By this device,
repetitive impact loads with variable duration and time courses were
exercised on coated cutting inserts. These loads approximately simulated
the developed ones in milling at various kinematics and process parameters.
The attained tool life up to the film fatigue failure was associated to a
critical force and an entry impact duration. The latter factors converge
sufficiently to the tool life in all investigated milling kinematics and
material cases.
Keywords: PVD coatings, milling, film fatigue, fatigue critical force, entry
impact duration
9:00am E4-2/G4-2-4 Cutting performance of PVD coatings during dry
drilling of sustainable austempered ductile iron (ADI), A. Meena
(anilme05@gmail.com), M. El Mansori, Arts et Métiers ParisTech, France
The present paper investigates the cutting performance of PVD coatings
during dry drilling of sustainable ADI material produced by the continuous
casting-heat treatment process [1]. The cutting tools used were PVD coated
carbide tools. SEM and EDS analyses were performed to investigate the
surface characteristics of PVD coatings. Cutting performance of different
coatings was evaluated by measuring cutting forces, chip types and undersurface
chip morphology. The phenomena and the causes of the tool wear
were studied too. The surface alteration at the machined subsurface was
confirmed from the hardness variation. It was shown that the major cause of
improved cutting performance and wear behavior of PVD coated tool is the
enhanced tribological adaptability of multilayer (Ti,Al,Cr)N coating. The
adaptability of multilayer (Ti,Al,Cr)N coating can be explained by the
formation of oxide layers on the cutting tool's surface, which further
increase tool wear resistance and lubrication at cutting zone. These oxide
layers reduce the severity of friction at the tool-chip interface by reducing
the strength of adhesion bonds at this interface.
9:20am E4-2/G4-2-5 Process design for the machining of high-strength
steels, F. Felderhoff (fabian.felderhoff@de.bosch.com), Robert Bosch
GmbH, Germany INVITED
In order to increase the efficiency and to reduce the emissions of internal
combustion engines for current and future generations of vehicles the
increase of the fuel injection pressure is needed.
In the field of diesel injection, pressures of up to p = 2500 bar are currently
implemented. As a result, stresses of the materials require special steels
with good levels of purity, so that the alloying with lead or sulfur to
improve machinability is no longer possible. Those steels are machined
with geometrically defined cutting edge in an annealed condition, which
79 Thursday Morning, April 26, 2012