Examination of the failed 1st stage

Examination of the failed 1st stage compressor blade #1 revealed cracks initiated from the anomaly region and propagated towards airfoil midchord under moderate load levels until final tensile overload separation occurred. Boroscopic inspection records did not show any initiation of corrosion or pitting marks on the first stage blades. The service environ- ment is not considered a corrosive environment. Looking at the inlet duct filters, the status was good and induced FOD is discarded from the root cause analysis.
Deep investigation of the anomaly region displayed morphological features of intergranular separation, and a golden coloration indicating that the fracture at this region was produced by tensile overload at temperature above 1000