Base material and coating degradation of a Frame 6-GTD 111 DS blade after 25,800 hours of service.
These photographs show variations of coating degradation between two locations near the leading edge of a Frame 7FA blade. The coating at location 2 (Picture 1) is in good condition, while at location 1 (Picture 3), the coating is completely degraded after 20,000 hours of service.
Degradation of material properties of a GTD 111 DS First Stage Blade after 49,000 hours of service.
GTD 111 blade with GT29 coating and 54,000 hours of service. Photo shows coating degradation in grid area ranging from 0 to 100 percent. Eddy current data (graph) of the same area shows that the eddy current signal increases in response to increasing degradation.
Material and Coating Degradation
Hot section component materials and coatings degrade when they are exposed to service. The extent of degradation depends on both metal temperature and service time. In a cooled component, the material and coating degradation varies from location to location. The extent of in-service degradation increases with increasing metal temperature and/or service time. In-service material and coating degradation lowers mechanical properties, which lower the service life of components.
Material Properties Evaluation
The service life of a gas turbine part is controlled by mechanical properties of the material. Southwest Research Institute (SwRI), staff has experience in material property evaluation, conducting extensive testing of both new and service-run components to generate material properties for life assessment and to determine the extent of material degradation during service.
SwRI has performed nondestructive evaluation (NDE) condition assessment studies to identify the degradation mechanisms for several coatings and base materials and extensive NDE testing of new and service-exposed components. Knowledge of a component condition is required to make prudent run, repair, and replacement decisions.
SwRI can offer you a full range of capabilities and experience in gas turbine technology including becoming an extension of your engineering department.
Contact us for more information about our gas turbine condition assessment capabilities, or how you can contract with SwRI.