Novel high temperature vacuum nanoindentation system with active surface referencing and non-contact heating for measurements up to 800 °C.

High temperature nanoindentation is an emerging field with significant advances in instrumentation, calibration, and experimental protocols reported in the past couple of years. Performing stable and accurate measurements at elevated temperatures holds the key for small scale testing of materials at service temperatures. We report a novel high temperature vacuum nanoindentation system, High Temperature Ultra Nanoindentation Tester (UNHT3 HTV), utilizing active surface referencing and non-contact heating capable of performing measurements up to 800 °C. This nanoindenter is based on the proven Ultra Nano-Hardness Tester (UNHT) design that uses two indentation axes: one for indentation and another for surface referencing. Differential displacement measurement between the two axes enables stable measurements to be performed over long durations. A vacuum level of 10-7 mbar prevents sample surface oxidation at elevated temperatures. The indenter, reference, and sample are heated independently using integrated infrared heaters. The instrumental design details for developing a reliable and accurate high temperature nanoindenter are described. High temperature calibration procedures to minimize thermal drift at elevated temperatures are reported. Indentation data on copper, fused silica, and a hard coating show that this new generation of instrumented indenter can achieve unparalleled stability over the entire temperature range up to 800 °C with minimum thermal drift rates of <2 nm/min at elevated temperatures.