Round Robin into Best Practices for the Determination of Indentation Size Effects

Abstract

The paper presents a statistical study of nanoindentation results obtained in seven

European laboratories that have joined a round robin exercise to assess methods for the evaluation of

indentation size e ects. The study focuses on the characterization of ferritic/martensitic steels T91 and

Eurofer97, envisaged as structural materials for nuclear fission and fusion applications, respectively.

Depth-controlled single cycle measurements at various final indentation depths, force-controlled

single cycle and force-controlled progressive multi-cycle measurements using Berkovich indenters

at room temperature have been combined to calculate the indentation hardness and the elastic

modulus as a function of depth applying the Oliver and Pharr method. Intra- and inter-laboratory

variabilities have been evaluated. Elastic modulus corrections have been applied to the hardness data

to compensate for materials related systematic errors, like pile-up behaviour, which is not accounted

for by the Oliver and Pharr theory, and other sources of instrumental or methodological bias. The

correction modifies the statistical hardness profiles and allows determining more reliable indentation

size e ects.