Testing the adhesion of hard coatings including the non-destructive technique of surface acoustic waves

It is generally accepted to distinguish two terms, “fundamental adhesion” and “practical adhesion” [1,2]. The term “fundamental adhesion” is used to describe the fundamental aspect that two materials adhere by the nature of the chemical bonds at the interface between them. This suggests quantifying the adhesion by the force necessary to break the interface bonds or by the specific work to sepa­ rate the two materials.