ABSTRACTDiscontinuities during both load and depth controlled continuous indentation tests have been ascribed to dislocation nucleation or multiplication and film fracture. In materials which exhibit permanent deformation prior to a discontinuity in loading, it is more likely that the phenomena is indeed controlled by film fracture, and not the rapid generation of dislocations. The current study has been undertaken to examine the properties of passivating films on engineering alloys. An electrochemical cell coupled with a scanning probe microscope and nanoindentation system allows growth and mechanical testing of passive films on an austenitic stainless steel as well as a titanium alloy. A complementary set of ex situ experiments shows the presence of deformation prior to film fracture with both load – depth sensing techniques as well as imaging the surface topography. The occurrence of excursions is shown in these materials to be linked directly with film fracture, rather than dislocation multiplication.
Influence of Vickers tip imperfection on depth sensing indentation tests
