With nickel-based superalloys reaching their limit in high-temperature gas turbines, further refinement and new alloys are required with improved mechanical properties. Small-scale mechanical testing – particularly nanoindentation – is of great benefit to alloy development, allowing hardness to be measured on small volumes of newly-developed materials.
In this work, we present high-temperature nanoindentation results on CMSX-4 and an Amdry-386 bondcoat up to 1000?C. We measure a room-temperature hardness of 4 GPa and modulus of 110 GPa, matching well with literature values. A peak hardness of 5.5 GPa is seen at 400?C, after which the hardness rapidly falls to 0.5 GPa at 1000?C. The Amdry-386 bondcoat matches this behavior closely. This behavior is explained with regards to the deformation processes in L12 crystal structures and the stress states during nanoindentation.
A discussion of the issues encountered during nanoindentation at extreme temperatures is also presented.