Investigation of the properties of candidate reference materials suited for the calibration of nanoindentation instruments

In order to guarantee the accuracy of nanoindentation instruments it is necessary to carry out a series of rather time-consuming and costly direct calibrations. Reference materials with known mechanical properties can be used alternatively for most of these calibrations. Compared with the direct calibration methods, reference materials excel by their lower costs and easy operation. Of high importance is the determination of the indenter tip geometry and the instrument’s compliance with suitable reference materials. Within the framework of the European Union (EU) a project “Certified Reference Materials for Depth Sensing Instruments” was started for the development of certified reference materials with traceability to metrological standards that can be used for the calibration of indentation instruments. As result of a review of candidate materials, a rather broad spectrum of material classes was considered for the investigation of their mechanical properties. The selected candidate materials represent wide ranges of elasticity and hardness. The investigations concentrate on indentation tests. In a first step, the investigations are directed at the determination of the homogeneity of hardness and indentation modulus as well as the propensity to cracking, definition of working load range, the influence of surface roughness, and the effects of different indenter geometry.