ABSTRACT
For many years the hardness of bulk materials and thick coatings
has been determined by optical analysis of indentation marks. The
development of thin coatings deposited by techniques such as phys-
ical vapor deposition (PVD) and chemical vapor deposition (CVD),
to improve wear resistance, led to the requirement to measure their
properties at a smaller scale. Initially such coatings were typically
relatively thick (e.g., ∼10 μm) and microhardness measurements could be performed to determine their hardness. However, as the
thickness of the films reduced the reliable determination of their
hardness by conventional optical means became impossible. Depth-
sensing indentation (DSI) instruments have been developed to
address this need and have become increasingly popular. The test
technique is also called instrumented indentation testing (IIT) or
nanoindentation and has progressed sufficiently for standardization
to be required with the first international standard for DSI
being released in 2002 and is currently in revision [1]. Provided
instruments are well calibrated the data from nanoindentation
tests are routinely analyzed by well-established contact mechanics
treatments to provide the reduced elastic modulus and the hardness
(or more strictly the mean contact pressure) of the test sample
[2-3]. Conversion between nanoindentation hardness and Vickers
hardness requires a little care. In addition to knowledge of the
indenter geometry the actual contact areas used in the two
definitions of hardness are slightly different necessitating the need
for a geometric correction factor.
