Indentation strain, reduced modulus and the determination of the elastic modulus of thin coatings using nanoindentation

Results from several series of experimental investigations are described, which, it is hoped, will increase our understanding of the distribution of plastic strain around spherical and Vickers indentations in metals. It is shown that the plastic strains around spherical and Vickers indentations are much higher than the traditional values. Experiments made using elastic cones and elastic substrates have also been used to highlight the inaccuracies which arise due to the use of the “reduced modulus” for analysing load versus displacement data obtained using pointed indenters. The final part of the paper describes the successful use of a new analytical model for deconvoluting the elastic modulus of a thin film deposited on a hard substrate using nanoindentation experiments