Scratch Testers are dedicated instruments for characterizing the surface mechanical properties of thin films and coatings, e.g. adhesion, fracture and deformation. The scratch tester’s ability to characterize the film-substrate system and to quantify parameters such as friction and adhesive strength, using a variety of complementary methods, makes it an invaluable tool for research, development and quality control.
This technique involves generating a controlled scratch with a sharp tip on a selected area. The tip material (commonly diamond or hard metal (WC)) is drawn across the coated surface under constant, incremental or progressive load.
At a certain critical load the coating will start to fail. The critical loads are very precisely detected by means of an acoustic sensor (MST & RST) attached to the load arm but can also be confirmed and collated with observations from a built-in optical microscope. The critical load data is used to quantify the adhesive properties of different film – substrate combinations.
In addition to acoustic emission, the Scratch Testers measure the applied normal force, the tangential (friction) force and the penetration depth. These parameters, together with the acoustic emission data, provide the mechanical signature of the coating system.
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