Abstract
The aim of the present investigation is to understand the localised failure mechanism of diamond-like carbon (DLC) film during multiple load cycle nanoindentation. The DLC film investigated was 500 nm thick sputter coated on Si (100) wafer of 500 μm thickness. Multiple load cycle nanoindentation tests under diamond Berkovich and conical indenters were performed using a calibrated NanoTest at five different load ranges between 0·1 and 500 mN. Test results indicated forward deviation, no deviation and backward deviation of the force-displacement profile, which provided some insights to the mechanisms of localised film failure. During backward deviation, film failure starts from interfacial delamination. This was observed for a conical indenter in a particular load range (1-10 mN). An elastic finite element model during nanoindentation loading indicated that this was caused by the location of maximum stress near the interface. Forward depth deviation was observed for conical and Berkovich indenter at all the other load ranges.