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 are 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is discussed, using published results in Argon on glass-ceramic solid oxide fuel cell seal materials and previously unpublished nanoindentation measurements on single crystal silicon and polycrystalline tungsten using the NanoTest Xtreme in vacuum at temperatures up to 950 °C. Studies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/microtribological behaviour of wear resistant nitride-based and MAX-phase coatings are also briefly reviewed.

Elevated temperature repetitive micro-scratch testing of AlCrN, TiAlN and AlTiN PVD coatings

“…In this study ramped load micro-scratch tests and repetitive micro-scratch tests were The critical load data were previously reported in [24] and [32]. L c1 = cohesive failure or unloading failure and L c2 = total failure in front of the probe.…”

“…As the load increased L c1 (= onset of cracking or unloading failure) and L c2 (= total failure in front of the probe) failures were observed. The critical load data from progressive load microscratch tests at 25 and 500 ºC have previously been reported in [24,32] and are shown in…”

Non-Newtonian Flow to the Theoretical Strength of Glasses via Impact Nanoindentation at Room Temperature

“…The latter is realized by accelerating the tip into the sample by releasing a controlled elastic deformation introduced into the tip mount, and collecting the position-time-signal at a high acquisition rate during impact and several subsequent rebounds. By using different tip geometries and a high temperature setup, such experiments could span a wide range of strain rates (10 −4 –10 5 s −1 ) and temperatures (≈150–1200 K) 14 , 15 entering regimes which have not been accessible so far by conventional methods (Fig. 1 ).…”