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Scratch
Testers are ideal instruments for characterizing the surface mechanical
properties of thin films and coatings, e.g. adhesion, fracture and
deformation. They can be used for all kinds of industrial coatings from the
plasma processed layers used in semiconductor and optical technology to the
decorative and protective coatings used for consumer goods and automobile
parts. The scratch tester’s ability to characterize the film / substrate
system and to quantify parameters such as friction force and adhesive
strength, using a variety of complementary methods, make it an invaluable tool
for research, development and quality control. The technique involves
generating a controlled scratch with a diamond tip on the sample under test.
The tip, either a Rockwell C diamond or a sharp metal tip, is drawn across the
coated surface under either a constant or progressive load.
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a certain critical load the coating will start to fail. The critical loads are
detected very precisely by means of an acoustic sensor attached to the load
arm together with observations from a built in optical microscope. The
critical load data are used to quantify the adhesive properties of different
film - substrate combinations. In addition to acoustic emission the scratch
testers measure the load normal to the coating, the tangential or friction
force, and also the penetration depth. These
parameters, together with the acoustic emission, constitute a unique signature
of the coating system
under test. |
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