Metallurgical evaluation of HPT disk internal bore indications/cracks and subsequent root cause identification associated with contamination

Following a commercial engine field event in 2016 related to an internal anomaly found in the HP turbine disk bore, an initiative was implemented by GE Aerospace to perform enhanced ultrasonic inspections of similar fielded disks on an opportunistic basis. As a result, a series of parts were found with small rejectable sub-surface ultrasonic indications. All of the parts were forgings derived from the same heat/extrusion of PM billet. The metallurgical evaluation confirmed the indications to be the result of fatigue cracks growing from internal material anomalies/contamination. The report describes the nature of cracking/anomalies and helped identify the source to allow for appropriate corrective action.