Characterizing the true stress-strain curve of CrAlN coatings by nanoindentation using finite element-reverse analysis

¹ Laboratoire de recherche LR18ES45 sis à l’institut préparatoire aux études d’Ingénieur de Nabeul, Université de Carthage, Campus Universitaire, 8000, Mrezga, Tunisia
² Higher Institute of Applied Sciences and Technology University of Gafsa, Gafsa, Tunisia
³ Applied Mechanics and Systems Research Laboratory (LR03ES06), Tunisia Polytechnic School, University of Carthage, BP 743, Rue El Khawarizmi, La Marsa, 2078, Tunisia.
⁴ Moroccan Foundation for Advanced Science, Innovation and Research (MAScIR), Rue Mohammed El Jazouli, Rabat Design Center, 10100, Rabat, Morocco.
⁵ Arts et Metiers Institute of Technology, LABOMAP, HESAM Université, UBFC, F-71250, Cluny, France

^* Corresponding author: This email address is being protected from spambots. You need JavaScript enabled to view it.

Abstract

This paper proposes a methodology to convert thin film nanoindentation load-displacement curves into tensile stress-strain curves. An optimization procedure, based on the trust-region reflective algorithm, is established to identify a unique set of three elastoplastic properties: Young’s modulus, yield stress and the strain hardening coefficient of the coating materials. The uniqueness issue of the optimization results is addressed by choosing initial guess parameters closer to the target values. The initial guess parameters are provided by the Jönsson and Hogmark model. The optimal elastoplastic properties of the coatings including, Young’s modulus (E), yield stress (σ_y) and work hardening exponent (n), are used to generate the true stress-strain curve. The presented methodology is validated on CrAlN monolayer coatings with different aluminum content. The results show good agreement between the simulated and the experimental nanoindentation load-displacement curves and as a result, the true stress-strain curve of the studied monolayer coatings is built successfully. These findings provide valuable insight for evaluating the elastoplastic properties of monolayered systems in order to optimize their structure.