A NEW TEST METHOD FOR THE INTRINSIC ABRASION RESISTANCE OF THIN COATINGS

A new method has been developed for checking the mechanical quality of thin coatings by determining their resistance to small-scale abrasion. The method is capable of determining the wear constants for the coating and the substrate individually, even for very thin coatings. The theory for imposed shape wear scars is introduced. Suitable parameters and test procedures are proposed and the repeatability, experimental scatter and general capability of the method are presented. The method has the following advantages: (1) The intrinsic abrasion resistance of the coating and the substrate are measured individually. In contrast to competing wear tests which evaluate the wear resistance of the composite rather than the coating and the substrate individually, these values are independent of the wear scar size. (2) Very thin coatings can be evaluated. In the most favourable situation, where the coating has a considerably higher abrasion resistance than the substrate, the wear constant of coatings of sub-micron thickness can be readily determined. (3) The small volume needed makes the test virtually non-destructive. For example it is fully possible to test the coating of a cutting insert before using it in a tool life test. (4) The craters are produced in a commercially available dimple grinder, which remains useful for its original purposes of preparing transmission electron microscopy samples and coating thickness measurements.