Comparison of hardness and Young's modulus by single indentation and multiple unloading indentation

Multiple partial unloading indentation is a useful technique for depth-dependent nanoindentation yielding up to 20 hardness and modulus values of different depth with one single measurement. A comparison between multiple partial unloading indentation and conventional single unloading technique is presented. A representative selection of materials (sapphire, TiN, DLC, tool steel, Ti alloy and aluminium) has been tested and it is found that both methods give comparable results. Soft materials as Al or Ti show certain deviations of about + 11 ± 4% in hardness and + 3.1 ± 1.2% for the modulus. For all other materials, the difference is + 2.2 ± 1.0% for the hardness and -2.1 ± 2.2% for the modulus. Possible reasons for these small systematic deviations will be discussed.