Nanoindentation provides a unique opportunity to probe the creep response of individual components or phases in complex microstructural materials that are not possible with conventional bulk testing techniques.
Elevated temperature creep resistance is important in many applications of high temperature materials. Understanding the fundamental relationship between creep and microstructure is a route to developing improved materials with enhanced stability at elevated temperatures.
Advantages of the NanoTest:
To measure indentation creep accurately it is essential that the test instrument exhibits ultra-low thermal drift across the entire measurement range. The NanoTest Vantage (-25 °C to 850 °C) and NanoTest Xtreme (-50 °C to 1000 °C) are renowned for their industry-leading thermal stability in conjunction with the flexibility to measure the widest range of sample geometries.
Electromagnetic force actuation combined with an extremely low drift National Instruments data acquisition system provides the excellent thermal stability necessary for long duration creep tests
Thermal drift hold period for an indentation on a polymer coating with the sample and indenter at 100 °C. Negligible drift rates are achievable – even at elevated temperatures – due to the superior thermal stability of the NanoTest.
Example – Solid Oxide Fuel Cell Materials
High temperature nanoindentation creep tests have been performed on a barium calcium aluminosilicate glass– ceramic (G18) used for seals that separate the fuel and air sides of a solid oxide fuel cell . The glass transition temperature for this material was 620 °C. Creep of the seal at the operating temperature of 800 °C can lead to early failure of the cell. Using a cubic boron nitride indenter the influence of a thermal “pre-ageing” process of 4 or 100 h at 800 °C was studied.
Indentation creep for G18 after 4h (left) and 100 h (right) thermal pre-ageing treatment
Marked differences in indentation creep resistance were observed from 550 °C (approaching its glass transition temperature). The creep resistance of the sample pre-aged for 100 h at 550 °C was only slightly worse than at room temperature. As the test temperature increased, both 4 h and 100 h samples showed more time-dependent deformation, although this was relatively lower after the longer duration of pre-ageing.
To find out more, download our creep testing application note using the link at the top of the page.
 Mechanical properties of solid oxide fuel cell glass-ceramic seal at high Temperatures, J Milhans et al, J Power Sources 196 (2011) 5599-5603.