Dureté des matériaux déposés en couches minces

Hardness of deposited thin films materials

¹ Maître de Conférences, Universite des Sciences et Technologies de Lille, Laboratoire de Mecanique de Lille (L.M.L.), URA CNRS 1441, IUT A GM P, Le Recueil, Villeneuve D'Ascq
² Professeur des Universités, Universite des Sciences et Technologies de Lille, Laboratoire de Mecanique de Lille (L.M.L.), URA CNRS 1441, IUT A GM P, Le Recueil, Villeneuve D'Ascq

Abstract

One of the most important feature of the hardness tests is that the hardness value depends of the applied load. In order to obtain a constant value, independent of the load, it is possible to use the presentation of Thomas, this presentation being related to the diameter of the impression. For bulk materials this does not bring any problem. But for films or coatings and for a large range of indentation loads, the apparent hardness is the result of contributions by both substrate and film or coating. Several models exist to account for this somewhat composite behaviour.

In this work we discuss the validity of the previously published models and a new model is presented in order to obtain the absolute hardness of thin films or coatings. On the basis of the relative plastic deformation of the coating and the substrate, this approach takes into account the role of the interface, introducing a function related to the substrate in the film hardness coefficient. The model is verified for titanium-nitride films on different substrate materials.