Numerical modeling of substrate effect on determination of elastic and plastic properties of TiN nanocoating in nanoindentation test

The wall of a ventricular assist device is composed of a titanium nitride (TiN) nanocoating deposited on a biopolymer. Because of difficulties of the precise measurement of the force–displacement data for the soft substrate of polymer and for the very thin hard nanocoating of TiN in the nanoindentation test, it is assumed that the correctness of the results measured for these coatings deposited on steel is better. The sensitivity of results of nanoindentation test reached for different substrates with respect to properties of TiN influences the accuracy of the determination of mechanical properties in inverse analysis. In this work it is proved that the use of the steel instead of the biopolymer as a substrate for the measurement of the properties of the TiN increases the accuracy of determination of the plastic properties of the coating TiN in the nanoindentation test without significant reduction the accuracy of the determination of the elastic properties.