An analysis of spalling in the microscratch test

An analysis of the microscratch test is presented for the case when extensive spalling occurs ahead of the scratch. In contrast to earlier models, attention is not focused on modeling the loads exerted on the film during a scratch test. Rather, the analysis relies on using the geometry of the spall to deduce the critical in-plane load for delamination and, hence, the interfacial toughness. It is shown that the extent of the spall is inversely proportional to the fourth root of the toughness. The model is used to compute the interfacial toughness between a Pt film and a NiO substrate using experimental data given in the literature. The predicted toughness is very consistent with the expected value. (C) 1998 Elsevier Science Ltd. All rights reserved.