The inclined impact test: A novel method for the quantification of the adhesion properties of PVD films

The inclined impact test constitutes a new reference to the prediction of the coatings’ impact failure, managing to approach loading stages of coated surfaces in different applications. In this experimental method, the repetitive impacts are applied on an oblique coated surface, which is loaded vertically and tangentially simultaneously. To calculate the occurring stress distribution in the loaded film's and substrate's region, an appropriate finite elements method (FEM) simulation is developed, which considers the mechanical elastic–plastic properties of all involved materials. In this way, critical equivalent stresses leading to a coating damage can be determined and moreover, the ratio of tangential to the normal stiffness between film and substrate can be quantified. This magnitude describes the adhesion strength and was further experimentally–analytically determined for coatings deposited on various adherent substrates. With the aid of the coating impact adhesion (CIA) metric, the film adhesion can further be qualitatively characterized and correlated to the film contact stiffness ratio.