This paper describes a method for determining the effective in-service material temperatures at specified locations of coated single crystal gas turbine blades. For this purpose, the microstructural changes of diffusion coated new and aged blades have been evaluated for the characteristic features and kinetics of degradation. After comparing alternative approaches, two indicators appear to be particularly useful: a) the extent of gamma prime coarsening and degradation in the blade interior and b) the combined layer thickness of the intermediate diffusion zone (IDZ) and the zone with topologically close-packed (TCP) precipitates below the coating. The applicability of the indicators was demonstrated for selected ex-service blades. With both indicators the relevant service temperatures can be inferred, although not to the same level of uncertainty. The thickness of IDZ+TPC layers can provide the temperature estimates to a relatively good accuracy as long as the layers remain sufficiently intact for the assessment.

YLI-OLLI Sanni;  RANTALA Juhani;  SALONEN Jorma;  AUERKARI Pertti;  HOLMSTROM Bjorn; 

2015-01-19

Forschungszentrum Jülich

JRC92103

978-3-95806-000-5,   

1866-1793,   

https://publications.jrc.ec.europa.eu/repository/handle/JRC92103,