Impact test

Principle of impact test
© Fraunhofer IST
Principle of impact test.
View on the test arrangement with impact ball.
© Fraunhofer IST, Falko Oldenburg
View on the test arrangement with impact ball.
Coating disruption after impact test on a piston ring. SEM analysis of top view and cross-section.
© Fraunhofer IST
Coating disruption after impact test on a piston ring. SEM analysis of top view and cross-section.

Coatings are increasingly being used where the strength of technical components is no longer sufficient. The increasing demands on technical components result from elevated temperatures as well as longer service intervals. The fatigue behavior and film adhesion are core parameters to guarantee the functional reliability of a coating.

The impact test is a supplementary test method for thin PVD and CVD hard material layers and is available at the Fraunhofer IST. A firmly clamped test ball exerts a cyclic load on the component to be tested. In addition to the conventional key parameters which describe a layer system, such as layer thickness, hardness and adhesion, the result of the impact test provides a statement about the fatigue strength of the layer system. Depending on the field of application, the impact test can be operated in the swelling permanent contact or in the lifting mode.

The layer system is analyzed either by light-optical or by SEM-EDX (see figures below) with regard to damage. A cross-section of the impact imprint also makes it possible to make a statement about material damages below the layer system.

The lifetime of coatings can be determined on flat as well as on convex curved components.

Light-optical analysis of the damage pattern.
© Fraunhofer IST
Light-optical analysis of the damage pattern.
EDX analysis of the damage pattern.
© Fraunhofer IST
EDX analysis of the damage pattern.