The information richness of imprints topographies obtained after Berkovich nanoindentation tests at grain scale is assessed for identifying all or part of the parameters of a single crystal plasticity law. In a previous paper (Renner et al., 2016), the strong potential of imprints topographies has been shown through a large experimental campaign conducted on nickel samples. A 3D crystal plasticity finite element modelling (CPFEM) of the nanoindentation experiment using the Méric-Cailletaud has also showed a large sensitivity of residual topographies to the indenter/grain orientation and to the plastic parameters, including the interaction matrix coefficients specifying the interactions between dislocations on different slip systems. This makes imprints topographies very good candidates to provide information for the single crystal parameters identification. The present paper focuses on the Méric-Cailletaud law parameters identifiability using residual topographies. A method is built to define the best well-posed inverse problem to ensure the parameters identification using a crystal plasticity finite element modelling updating (CPFEMU) method. An identifiability index proposed by Richard et al. (Richard et al., 2013) for measuring the information richness of the indentation curve is extended to the analysis of residual topographies. This index quantifies the possibility to achieve a stable/unstable solution using an inverse method. For the studied behaviour, the results show that eight of the nine Méric-Cailletaud law parameters can be identified using three topographies.

This study aims to model, by using a finite element method, the relationship between the hardness and the period Λ of metal/nitride multilayer coatings (Ti0.54Al0.46/Ti0.54Al0.46N)n in order to understand the increase of the hardness at the low periods [1] and then optimise the multilayer coating architecture to obtain the best mechanical properties. A 2D axisymmetric finite element model of the Berkovich nanoindentation test was developed. The coating was designed as a stacking of Ti0.54Al0.46 and Ti0.54Al0.46N nanolayers with, in the first hypothesis, equal thickness and perfect interface. The elastoplastic behaviours of the metal and nitride layers were identified by Berkovich nanoindentation experiments and inverse analysis on thick monolayer samples. The indentation curves (P-h) obtained by this model depend on the period Λ of the stacking. Simulated (P-h) curves were compared with experimental data on 2 μm thick films with different periods Λ ranging from 10 to 50 nm deposited by RF magnetron sputtering using reactive gas pulsing process (RGPP). The model forecasts are very consistent with the experience for the largest period but the model does not reproduce the hardness increase at the lowest periods. The Λ = 10 nm coating was analysed by electron energy loss spectroscopy (EELS) on a transmission electron microscope. Results show intermixing of the layers with the presence of nitrogen atoms in the metal layer over a few nanometers [1]. It was concluded that the metal/ceramic interface plays an important role at low periods. The addition in the model of a transition layer in the metal/nitride stacking, with an elastoplastic metal/ceramic medium behaviour, allows to reproduce the nanoindentation experimental curves. The thickness of this transition layer deduced from model updating method is in very good agreement with EELS observations.