Cracking of Pipe Assembly Exhaust of an Aeroengine of a Military Aircraft

摘要

The Pipe Assembly Exhaust belonging to engine of a military aircraft had cracked in-service. The crack was observed at change in section in the body portion of the pipe assembly exhaust. The part was made of stainless steel material of specification CRES 347/AMS 5512. The chemistry, hardness and microstructure of the part conformed to the specification requirements. Fractographic studies showed that features of fatigue failure on the fracture surface of the crack. Fatigue failure had originated at multiple locations from the outer surface of the part. Macro and micro examination of samples extracted close to and away from the failure location showed presence of weld beads at the change in section in the part. Cracks were also observed in some of the weldbeads and the cracks had initiated from the weld face. The presence of weld beads at the change in section in the body of the pipe assembly exhaust was inexplicable. Nevertheless, these weld beads had acted as weak area and caused failure/cracking of the part in-service by fatigue.