Hardness determination by means of a FEM-supported simulation of nanoindentation and applications in thin hard coatings

In nanoindentation procedures, due to indenter tip form deviations from its ideal geometry and the limited indentation depth, the contact region between the indenter and the specimen cannot be accurately determined. In this way, up to now, the hardness values are approximated by means of empirical methods with restricted accuracy, in a wide range of applications. In the frame of the present paper, the contact area between the indenter and the specimen during loading and unloading nanoindentation phases are defined through FEM supported calculations, thus enabling the hardness determination after various methods. The material constitutive laws required in these calculations are predefined by means of nanoindentations and a FEM-based evaluation of the corresponding results, considering the actual indenter tip geometry. In order to check the validity of the developed hardness determination procedure, various materials and coatings were tested through nanoindentations and their Vickers HV and indentation hardness H-IT were computed and experimentally verified versus the indentation depth, by means of SEM-supported observations of the occurring impressions. Using the described methodology, coating thickness and substrate material effects on the film hardness can be predicted. Corresponding examples are illustrated in the present paper. (c) 2005 Elsevier B.V. All rights reserved.