A Study of the Affected Layer and Stress Corrosion Crack of Ultra-high-strength Steel (300M) for Aircraft Parts

Mechanical components that support structures in aerospace and power generation industries requirehigh-strength materials. Particularly, in the aerospace industry, aluminum alloys, titanium alloys, and compositematerials are increasingly used due to their high maneuverability and durability to withstand low temperatureextreme environments; however, ultra-high-strength steel is still used in key components under heavy loadssuch as landing gears. In this paper, the fault cause analysis and troubleshooting of aircraft parts made ofultra-high-strength steel (300M) broken during normal operation are described. To identify the cause of thedefect, a temporary inspection of the same aircraft was performed, and material testing, non-destructiveinspection, microstructure examination, and fracture area inspection of the damaged parts were performed. Fracture analysis results showed that a crack in the shape of a branch developed from the tool mark in thedirection of the intergranular strain. Based on the results, the cause of fracture was confirmed to be stresscorrosion.