Adhesion evaluation of PVD coatings to aluminium substrate

In this study the adhesion of physical vapour deposition coatings to aluminium substrate has been evaluated using a modified test similar to the scratch hardness method. The technique relies on the development of a number of scratches of different width on the coated surface produced at a range of loads. Metallic titanium and titanium nitride coatings of different thicknesses were deposited by a PVD technique. The effect of coating structure, process parameters, and the presence of an interlayer between the coating and the substrate was investigated. Experimental data show that the technique can be used to evaluate the adhesion of PVD coatings to aluminium substrates. The sensitivity of the test method is sufficiently high to characterise between coatings produced under different conditions, but the interpretation of the results is not always straightforward. Comparison of the results indicate that the method could provide useful information on coating performance, although it suffers from many problems associated with the critical load in the conventional scratch adhesion test.