Metallurgical Analysis of Temperature Monitored Gas Turbine Blades FREE

A thorough visual inspection and metallurgical analysis of the gamma prime microstructure of GE Frame 6 first row blades has been performed after they were taken out of service. During the last few years of their service life these blades have been temperature monitored using a radiation thermometry system. The monitoring program included the registration of blade temperature profiles as well as temperature transients during start-up and shutdown. The temperature data were correlated to other gas turbine parameters. This radiation thermometry system revealed significant temperature differences between blades (up to 27°C). Accurate spatial information has been obtained using a high-resolution radiation thermometer having a spot size of 1.2 mm and 1.8 MHz electronic bandwidth. There is a clear relation between the observed blade temperatures and the degradation of the material structure. The results clearly show the capabilities of radiation thermometry in indicating blades with potential problems with respect to creep.