Quantitative acoustic microscopy for determination of properties of hard coatings

For quantitative assessment of the properties of hard coatings there is an increasing demand for testing methods with high reliability of the test res ults, especially concerning the independence of the method and the comparab ility between different laboratories. This includes the knowledge about all the factors which influence the test procedure itself, determination of be st testing conditions, testing of these conditions in round-robins to get a view of the comparability of results, and formulation of guidelines for st andardization. In a European project several test methods for hard coatings on steel were investigated for this purpose and the elastic moduli of the coating and coating thickness were determined non-destructively by means of quantitative acoustic microscopy, This method and the instruments availabl e had not yet been certified in the fields of coatings simply owing to the absence of standardised signal processing, followed by the determination of sound velocities and materials parameter extraction. For this purpose four laboratories carried out investigations and measurements on reference samp les and on two types of hard coatings (titanium nitride and C-doped chromiu m) on M2 tool steel.