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Nanotribology of Hard Thin Film Coatings:
A Case Study Using the G200 Nanoindenter
Application Note
Introduction is also important in many applications
Thin film coatings are extensively to understand the deformation behavior
used in various applications, such as of the film due to lateral movement of
microelectronics, data-storage media, sharp contacts, which is referred to
surgical tools, biomedical prosthetic as nanotribology. Most thin film hard
components, machining tools, turbine coatings should possess two important
blades etc. Along with some functional characteristics, low coefficient of friction
improvements, these thin coatings also and a high strength adhesive bonding
significantly enhance the mechanical with the underlying substrate. In some
reliability of the components. Hard applications a low wear rate under
thin films provide the resistance cyclic scratching may also be important,
to mechanical deformation that but it was not a critical concern for the
the components need during their thin film with extremely high hardness,
application. With the advancements in discussed herein. Nanoindentation with
nanomaterials research, new thin film lateral force measurement capability is
systems -- often only a few 100's of an ideal tool to address the tribological
nm -- are being developed to improve characteristics of such thin film materials
the performance of thin coatings in at nano length scales.
all of these technologically important
areas. Hence, it is becoming more and Before we discuss the tribological
more important to design new test properties of a thin hard coating,
methods that addresses the relevant it is important to differentiate the
deformation mechanisms in thin films, measurements using a nanoindenter with
which are not suited to be characterized those performed at micro/macro-scale.
by the conventional test methods and Tribology being a subject of interest
standards. for long time, there are quite a few
international standards for tribological
Nanoindentation has been a method measurements, some of which also
of choice to characterize mechanical include measurement on thin coatings.
properties of small volumes of materials, However, according to all the standards,
such as thin films. This is especially true the measurements are performed with
since an analytical method has been a probe of much larger length scale
proposed to measure the properties (usually 100's of microns) compared to
of the films without the substrate the coating material. Although the larger
effect. Besides measuring the elastic probes enable an optical investigation
modulus and hardness of thin films, it of the scratched region, the forces
(a) (b)
Apparent Elastic Modulus (GPa)
Hardness (GPa)
Displacement Into Surface (nm) Displacement Into Surface (nm)
Figure 1. Continuous stiffness measurement of (a) elastic modulus and (b) hardness for thin film coating on WC-Co substrate. Note the thin film and substrate
have similar elastic modulus, but the thin film is much harder than the substrate. Measured properties in the greyed region (below 50 nm) are artifacts of the
tip shape.
required for scratching a hard coating to measure the critical parameters for as a function of penetration into the
often surpasses any realistic values of these thin films. Hence, a nanoindenter, surface. Details of continuous stiffness
forces these coatings encounter during where the force and displacement measurement (http://cp.literature.
their operation. The measurements are calibrated in compliance with agilent.com/litweb/pdf/5990-4183EN.
with the larger probes are also affected international standards is more suitable pdf) can be found elsewhere [Hay et al.,
by significant deformation of the for addressing this need for the future Experimental Techniques 34, 86