Extreme nanomechanics: vacuum nanoindentation and nanotribology to 950 °C

Abstract

Elevated temperature mechanical and tribological properties can be more relevant for practical wear situations than corresponding measurements at room temperature. However, high temperature nanomechanics and nanotribology is highly challenging experimentally. To overcome these challenges the NanoTest*** has been developed with active heating of the indenter and sample with resistive heaters, horizontal loading, patented thermal control method and stage design. By separately actively heating*** and controlling the temperatures of indenter and sample their temperatures can be precisely matched so that there is no heat flow and minimal/no thermal drift during the high temperature indentation,*** and measurements can be performed as reliably as at room temperature. Above 500 °C it is beneficial to use a cubic Boron Nitride indenter with gas purging to limit oxidation of samples. To achieve higher temperatures without indenter or sample oxidation an ultra-low drift high temperature vacuum nanomechanics/tribology system capable of testing to*** much higher temperatures has been recently developed (NanoTest Xtreme). The influence of time-dependent deformation on elevated temperature nanomechanical behaviour is discussed, using published results in Argon on glass-ceramic solid oxide fuel cell seal materials and previously unpublished nanoindentation measurements on single crystal silicon and polycrystalline tungsten using the NanoTest Xtreme in vacuum at temperatures up to 950 °C. Studies of the elevated temperature nano-/micro-tribological*** behaviour of wear-resistant*** nitride-based and MAX-phase coatings are also briefly reviewed.