Title : A Case Study of Austenitic Stainless Steel Air Tube Fracture from an Aircraft Gas Turbine Engine
An air tube made of austenitic stainless steel (grade 347) that belonged to an aircraft gas turbine engine was found to have fractured. The fracture was found along the edge of a circumferential weld (HAZ) between the flange and the tube. Fractographic examination revealed that one half of the fracture surface was due to intergranular cracking, whereas the other half was predominantly transgranular cracking. The transgranular fracture was a result of High Cycle Fatigue (HCF) mode of propagation which had originated from the intergranular fracture zone. Metallographic examination across the fracture confirmed that the material had been sensitised which was considered to be caused by prolong exposure of the tube material to high temperature air in the range of 500ºC to 900ºC. The evidence suggested that the intergranular cracks was initiated due to sensitisation which was likely to have weakened the material sufficiently to allow a HCF failure mode to occur and resulted in the final failure of the tube.
What will audience learn from your presentation?
The presentation is a case study that describes a problem encountered in an aircraft gas turbine engine. It explains the materials characterization techniques and methodologies commonly used in the aerospace industry to determine the root cause of the failure. With the root causes identified, steps can be taken, for example by improving the design of the product and/or reviewing of in-service conditions to prevent similar failure occurrence.