A COMPARISON OF 3 MICROINDENTATION HARDNESS SCALES AT LOW AND ULTRALOW LOADS

Indentation hardness tests were performed on thick, fine-grained, elec tro-formed deposits of copper and nickel using Knoop, Vickers, and Ber kovich indenters. The latter type of indenter was used for shallow pen etrations (85-1750nm), and results are reported in terms of nanoscale hardness (NH) numbers. Knoop and Vickers indenters were used with appl ied loads of between 0.15 and 0.98 N, and at the lowest load, produced indentation depths comparable to the larger ones obtained with the Be rkovich indenter. The NH numbers became very sensitive to penetration depth when the penetration depth was less than certain critical values . NH numbers for Cu and Ni were higher than those for Knoop and Vicker s testing at comparable penetration depths. Applying indenter area fun ction corrections to calculate hardness numbers (i.e., considering pro jected area versus facet contact area) resulted in a closer correlatio n between microhardness and nanohardness scales; however, changes in t he tip shape because of wear or other imperfections.can lead to inaccu rate calculation of NH numbers at the lowest loads. Results also sugge st that the interconversion of lowload hardness numbers from one scale to another can be material-dependent.