Analysis of spherical indentations of coating-substrate systems: Experiments and finite element modeling

The influence of surface layers and thin coatings on the load-bearing capacity of elements under contact load conditions has yet to be sufficiently described theoretically. In this study, the deformations of coated surfaces were analyzed using spherical indentation and finite element method (FEM) modeling. The paper presents a complex procedure of indentation result analysis, based on the transformation of load-penetration depth curves into stress–strain curves. Such a procedure was applied for 0.7–2.4 μm thick titanium nitride (TiN) coatings deposited by the Pulsed Laser Deposition (PLD) technique on steel substrates. Indentation experiments showed that the critical stress for fracture of TiN coatings deposited on steel substrates is 2–3 GPa. The result of the theoretical analysis, FEM modeling and experiments is the map of failure, which shows elastic, elastic–plastic and fracture regimes of the tested coating-substrate systems.