Interfacial Stresses and Degradation of Oxide Scale and Substrate Interface at High Temperature

Interfacial analysis utilizing interfacial indentation methodology (where micro/nano indentation is performed at the oxide scale/substrate interface to create and propagate cracks at the interface) was completed for the 14,000 and 20,000 hours, 800oC surface modified specimens. The localized oxide thickness and crack lengths were measured after applying loads ranging from 0.2 to 1.8 N. Post-processing of the results to date indicate that the critical load for surface blasted (SB) surface modified specimens is greater than the equivalent surface grind (SG) surface modified specimens which is indicative of a ~ 25% increase in interfacial strength in the SB specimens in comparisons to the SG specimens. However, more data is needed to further quantify the interfacial strength and to reduce any uncertainty due to the approach applied.